Best Inorganic Chemistry Frontiers Covers of 2021

We are delighted to announce the Best Inorganic Chemistry Frontiers Covers of 2021!

Read below the scientific papers.

A red-light-chargeable near infrared MgGeO3:Mn2+,Yb3+ persistent phosphor for bioimaging and optical information storage applications

Inorg. Chem. Front., 2021,8, 5149-5157
https://doi.org/10.1039/D1QI01158H

Issue 24 Volume 8 Outside Front Cover

Binuclear metal complexes with a novel hexadentate imidazole derivative for the cleavage of phosphate diesters and biomolecules: distinguishable mechanisms

Inorg. Chem. Front., 2021,8, 2684-2696
https://doi.org/10.1039/D1QI00108F

Issue 11 Volume 8 Inside Front Cover

Designing lanthanide coordination nanoframeworks as X-ray responsive radiosensitizers for efficient cancer therapy

Inorg. Chem. Front., 2021,8, 3433-3439
https://doi.org/10.1039/D1QI00442E

Issue 14 Volume 8 Inside Front Cover

Congratulations to the winners of Best Inorganic Chemistry Frontiers Covers of 2021!

We expressed our sincere appreciation for all the support and contributions from our authors, reviewers, and readers in the past 2021.

Looking forward to receiving your high-quality work in 2022.

Happy Chinese New Year!

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A highly active and E-selective Co catalyst for transfer-semihydrogenation of alkynes

The efficient semihydrogenation of internal alkynes to selectively produce either E– or Z-alkenes is one of the main challenges in homogeneous catalysis. Numerous systems were reported in the past, however, such reactions typically require either the use of gaseous hydrogen at high pressure, noble metal catalysts, or rather high catalyst loading at long reaction times, the latter resulting in alkene isomerisation or overreduction to produce alkanes. Amine boranes such as ammonia borane (H3B·NH3) are known to be well-suited for transfer hydrogenation reactions, providing stoichiometric amounts of H2 either by dehydrogenation (i.e. H2 production), followed by hydrogenation, or by stepwise hydride and proton transfer to an organic substrate. Homogeneous precatalysts based on the Co(II) oxidation state have been reported in the past, however, mechanistic insights into such systems were rather limited to date.

Recently, the groups of Jiao and Beweries at LIKAT Rostock have demonstrated that PNN(H) Co(II) complexes serve as very efficient precatalysts for the selective formation of E-alkenes at very mild conditions, suing MeOH and H3B·NH3 as the hydrogen source. This reaction is suggested to take place exclusively via the Co(II) oxidation state, which was corroborated though a combination of control experiments, EPR spectroscopy, and DFT analysis. Key feature for the high activity of this Co system is the proton responsive PNN(H) ligand, possessing a pyrazole fragment that undergoes deprotonation during catalyst activation. The results presented herein could be relevant for the design of other proton responsive ligands for non-noble metal free transfer hydrogenation reactions.

Corresponding author:

PD Dr. Torsten Beweries (Leibniz Institute for Catalysis, Rostock)

Torsten Beweries is head of the department Coordination Chemistry and Catalysis at the Leibniz Institute for Catalysis in Rostock (Germany). He received his PhD in Chemistry at LIKAT in 2008, working on the coordination chemistry of hafnocenes. He then moved to the University of York (UK) for a postdoctoral stay with Prof. Robin N. Perutz in 2009, working on late transition metal complexes for halogen bonding. He returned to LIKAT in 2010, where he established an independent research group. The research field of PD Dr. Torsten Beweries is organometallic chemistry and homogeneous catalysis with focus on new pincer ligands and complexes, main group polymers, and unusual metalacyclic systems. He is the author of 91 articles indexed by SCI and cited more than 1600 times with an index H = 23.

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Unprecedented Organometallic Rare Earth Complexes Containing a Large, Flexible Salophen Ligand

Organometallic chemistry of the rare earth and actinide elements has been a driving force for the development of novel functional materials and catalysts for decades, giving rise to impressive advances in the fields of single-molecule magnetism, luminescence, and polymer sciences. Excitingly, organometallic approaches have always been on the forefront of fundamental chemistry and allowed breakthroughs in the field, not only with the lighter metals but also some of the heaviest actinide candidates. The inherent reactivity of organometallic compounds owing to the apparent labile and reactive metal-carbon bonds renders the isolation and characterization of such molecules exceptionally challenging, especially when aiming at polymetallic rare earth complexes, and is therefore underdeveloped to this date. Consequently, the exploration of suitable synthetic routes to access bridged organometallic metallocene complexes is of great interest for the rare earth and more general inorganic chemistry community.  

Recently, the group of Selvan Demir at Michigan State University has demonstrated that two rare earth metallocene fragments are able to capture the tetradentate salophen ligand, giving rise to the first series of dinuclear salophen-bridged rare earth metallocene complexes with the metals yttrium, gadolinium and dysprosium, Figure 1. These molecules also constitute the first metallocene salophen complexes for any metal ion. Remarkably, the flexibility of the salophen bridge allows the binding pockets to face outwards upon complexation to the metal ions which is a rare, yet intriguing, coordination mode. Consequently, a substantial separation of the metal centers (7.858 – 7.895 Å) occurs leading to weak electronic or magnetic communication between the rare earths. Since the magnitude of magnetic exchange coupling between paramagnetic metal centers and/or organic radical is crucial for the generation of better-performing multinuclear single-molecule magnets,  the magnetic communication in these salophen complexes was explored. 

Figure 1. (A) Schematic view of the salophen-bridged rare earth metallocene complexes. (B) Structure of the rare earth molecules as obtained through single-crystal X-ray diffraction. (C) Arial view of the calculated highest occupied molecular orbital.

The dynamic magnetic properties of the paramagnetic dysprosium complex revealed characteristics of single-molecule magnet behavior, while the static magnetic susceptibility data collected for the paramagnetic gadolinium complex allowed quantification of the magnetic exchange, Figure 2. The determined coupling is of similar magnitude to other polynuclear rare earth complexes containing diamagnetic bridging ligands. DFT calculations on the diamagnetic yttrium conger revealed negligible orbital overlap between the metal center and the salophen ligand in the highest occupied molecular orbital, Figure 1, which may account for the weak magnetic coupling in the paramagnetic variants.

Notably, the lowest unoccupied molecular orbital might be able to be populated with an unpaired electron. Radicals, innate to unpaired electrons, promote strong exchange coupling when placed between rare earth magnetic moments and are, thus, extremely sought-after in the fields of single-molecule magnetism and spintronics. Excitingly, cyclic voltammetry measurements of the salophen

Figure 2. (A) Electron uptake of the dysprosium molecule via electrochemistry. (B) Single-molecule magnet features of the dysprosium complex.

complexes revealed a quasi-reversible feature attributed to the reduction and oxidation of the salophen bridge on the timescale of the electrochemical experiment, Figure 2. This paves the way for chemical reductions of these molecules to generate coveted metal-radical compounds in the future. Noteworthy, chemical functionalization of the salophen backbone may readily be attained which serves as an additional path to augment magnetic coupling and as such highlights the enormous potential of the salophen ligand in organometallic chemistry.

Selvan Demir is an Assistant Professor of Chemistry at Michigan State University. She earned her Dr. rer. Nat. at the University of Cologne researching on scandium solid state chemistry with Prof. Gerd Meyer and scandium organometallic chemistry with Prof. William J. Evans at the University of California, Irvine. Subsequently, she focused on lanthanide-based single-molecule magnets and porous aromatic frameworks with Prof. Jeffrey R. Long at the University of California, Berkeley, and worked on transuranics with Dr. David K. Shuh at the Lawrence Berkeley National Laboratory. Afterwards, she took up a junior professorship of inorganic chemistry at the University of Göttingen. Since 2019, she researches with her group at Michigan State University, on various areas surrounding the chemistry of the rare earth elements and actinides. The research group focuses mainly on organometallic chemistry, small molecule activation, single-molecule magnetism, and lanthanide/actinide separations. A particular emphasis is also on heavy p-block element and uranium chemistry.

 

 

 

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Enantioselective chiral sorption of 1-phenylethanol by homochiral 1D coordination polymers

Amongst the myriad uses of metal-organic frameworks (MOFs) and coordination polymers, separation of complex mixtures, either gaseous or in solution, is one of the most promising applications due to the regular array of well-defined pores. Integration of specific points of interaction that are complementary to the targeted guest species can provide highly selective materials. In particular, precise control of the 3D space within pores may provide a mechanism for enantioselective discrimination for which the exact spatial arrangement of multiple sites of interaction is paramount.

The vast majority of research in this area is driven by 3D metal-organic frameworks, often those possessing permanent porosity. However, for solution-based applications this need not be a prerequisite and materials comprising lower dimensionality coordination polymers may be just as effective is they contain solvent-filled pores.

Recently the group of David Turner at Monash University has shown that a 1D coordination polymer, with pores formed by alignment of loops within the 1D chain, is capable of sorbing 1-phenylethanol with a good degree of enantioselectivity (Figure 1). A closely related material shows no such selectivity, and a reduced uptake capacity, highlighting the importance of structural match between the host framework and the analyte. Ground samples showed higher uptake than unground crystals for the active material, suggesting an influence of surface area or ease of permeation into the solid. Both static (soaking) and dynamic (“micro-LC”) methods showed enhanced uptake of one enantiomer from a racemic solution of 1-phenylethanol, albeit not perfect separation. The group was also able to crystallographically determine the binding site of the preferred enantiomer (Figure 2), showing an array of hydrogen bonding interactions that lie behind the enhanced uptake of one enantiomer over the other.

These results highlight the potential of non-3D coordination polymers in chemical separations and demonstrate the array of host-guest interactions that are required for separations of very similar compounds.

Figure 1. The chiral material contains guest-filled pores resulting from the alignment of loops within the 1D coordination polymer.

Figure 2. The preferred enantiomer of the guest is found crystallographically within the binding pocket, highlighting the array of interactions that hold it in place and provide the enantioselectivity.

Corresponding Author:

David Turner is a Senior Lecturer in the School of Chemistry at Monash University, Australia. After receiving his PhD in 2004 from King’s College, London, he held a number of fellowships at Monash University prior to joining as a Faculty member. Research in the Turner group revolves around metallosupramolecular assemblies, exploring both coordination polymers/MOFs and coordination cages with a particular emphasis on chirality. Dr Turner has published over 130 papers, in addition to two books, attracting almost 5000 citations and an h-index of 32.

https://research.monash.edu/en/persons/david-turner

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A New 2D Layered Aluminophosphate |Hada|6[Al6(PO4)8](H2O)11 Supported Highly Uniform Ag Nanoparticles for 4-Nitrophenol Reduction

Since Wilson and Flanigen found the first microporous aluminophosphate (AlPO) in 1982, the synthesis of AlPO materials with novel frameworks and study their potential properties, such as adsorption, catalysis, and separation, has attracted intense interest of researchers. As the main family of AlPO based materials, 2D layered materials show a rich variety of structures and compositions depending on the diverse coordination and connection modes of Al and P atoms. In recent years, 2D materials, possessing highly exposed surfaces and diverse structures, have become a dramatic category of supports. However, 2D molecular sieves are serving as catalyst supports are very few.

Recently, Prof. Jiuxing Jiang at Sun Yat-sen University and Dr. Jiang-Zhen Qiu of Zhongkai University of Agriculture and Engineering synthesized a new 2D layered aluminophosphate compound by adopting rigid and bulky template of 3,5,N,N-tetramethyladamantane-1-amine (ada) through hydrothermal conditions, which is named the Zhongkai University of Agriculture and Engineering NO.1 (ZHKU-1), with the composition |Hada|6[Al6(PO4)8](H2O)11. The structure of ZHKU-1 was constructed from the alternate connection of AlO4 and triply bridged PO4 tetrahedra ([O=PO3]3-) to form a 4, 6, 12-net (Figure 1). The inorganic sheets are linked and separated by protonated amine and H2O molecules by extensive H-bonds, giving a new 2D structure with an interlayer space of 19.6 Å.

Figure 1 Crystal structure figures of ZHKU-1

ZHKU-1, as a 2D material with a more exposed surface, could be adapted for encapsulating metal nanoparticles (NPs). Ag species are immobilized on the supports of ZHKU-1 by UV reduction and deposition, forming the catalyst of Ag@ZHKU-1 with high loading of 4.9 wt%. The HRTEM images reveal the highly uniform Ag clusters with visually observed sizes of 1.9 nm (Figure 2).

Figure 2 The characterizations of Ag@ZHKU-1 for HRTEM and corresponding mapping images

Since 4-nitrophenol (4-NP) is a notorious industrial pollutant, Ag@ZHKU-1 is applied to the model reaction for 4-NP reduction. The catalytic results show that the reduction reaction of 4-NP into 4-aminophenol could be completely performed within 75 s in NaBH4 solution (Figure 3). Moreover, the catalytic activity was almost the same, with almost 99% conversion after eight cycles. The remarkable catalytic activity and recyclability of Ag@ZHKU-1can be attributed to the high dispensability of Ag nanoclusters confined to the 2D support, which provides more accessible Ag active sites to 4-NP.

Figure 3 Catalytic activity and recycling tests for 4-nitrophenol reduction are over Ag@ZHKU-1 catalyst

This work reports a new 2D layered aluminophosphate compound, which expends the aluminophosphates family. Furthermore, the confinement of metal Ag on this new layer structure through photodeposition gives rise to a small size (~1.9 nm) of AgNPs with homogeneous dispersion. The catalyst of Ag@ZHKU-1 shows excellent catalytic activity and high conversion for 4-nitrophenol reduction. This work is significant for designing 2D aluminophosphate materials to confine small metal nanoparticles for catalytic application.

Prof: Jiuxing Jiang (ORCID: 0000-0001-9664-3235). I received Ph.D degree from Jilin University in 2010. Afterward, I spent 5 years for a Post Doc. stay in Instituto Technologia Quimica (UPV-CSIC) in Valencia Spain supervised by Prof: Avelino Corma. After independent work in Sun Yat-sen University (2015-now), I keep my interesting on the topologically new zeolite synthesis (four three letter code, IRR, -IRY, -IFU, -SYT were granted by Structure Committee of Internation Zeolite Association), and zeolite based heterogeneous catalysis, such as: acid-base catalysis, catalytic ammonium synthesis, NH3-SCR for deNOx reaction, porous materials for energy storage, etc. I have published more than 20 high-impact journal articles, such as Science, Angew. Chem. Int, Ed, Chem.Sci, Chem. Mater. etc. Among them, the work on the synthesis and structure of zeolite ITQ-43 was published in Science, 2011, 333, 1131-1134 and was selected as annually breakthrough of 2011 by Science. Currently serve as a member of Zeolite Committee of Chinese Chemical Society and youth editorial member of Journal of Chemical Research in Chinese University.

Jiang-Zhen Qiu: She received her Ph.D. degree in 2019 from Sun Yat-sen University with M.S. Supervisor Prof. Ming-Liang Tong and Ph.D. Supervisor Prof. Jiuxing Jiang. In 2020, she was introduced to Chemical Engineering of Zhongkai University of Agriculture and Engineering as an “Excellent Doctor”. Her interested research fields include synthesizing new topological structures of zeolite and exploring multifunctional materials with novel functionalities such as light, conductivity, magnetism, or catalysis. Currently, she and her collaborators published 10 papers in related fields, such as Chem. Mater., Chem. Sci., Inorg. Chem. Front., Chem. Commun., Chem. Eur. J.

 

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Optimizing the relaxivity at high fields: systematic variation of the rotational dynamics in polynuclear Gd-complexes based on the AAZTA ligand

Magnetic Resonance Imaging (MRI) is one of the most important and prominent techniques in in clinical diagnostic medicine, in preclinical studies and in biomedical research. As well as many other imaging modalities, MRI also makes extensive use of contrast agents (CAs) that allow achieving remarkable improvements in medical diagnosis in terms of higher specificity, better tissue characterization and functional information. For the vast majority, the clinically used CAs are coordination complexes in which a GdIII ion is encapsulated within octadentate chelators based on polyaminocarboxylate anions and has a directly bound water molecule. Their use is widespread and is estimated to correspond to approximately 40 million administrations per year of GdIII chelates worldwide.

Their effectiveness (relaxivity; the increase in the relaxation rate R1 of the water protons normalized to a 1 mM concentration of the paramagnetic ion) at the magnetic fields of clinical interest is dominated and limited by the fast rotational dynamics and tends to decrease with the increased magnetic field. However, the current trend in MRI development is towards higher magnetic field strengths and most scanners operate at 1.5 or 3 T, while there is increasing use of those at 7 T. Therefore, a different approach for the relaxivity enhancement of Gd-based CAs becomes necessary for the modern high-field systems.

Recently, the group of Mauro Botta and colleagues from the University of Eastern Piedmont in Alessandria (Italy) investigated the optimization of the efficacy of Gd-based CAs, between 1 and 7 T, by systematically modulating the rotational dynamics through the synthesis of polynuclear systems containing between two and eight GdIII chelates (Figure 1).

Figure 1. [Gd(AAZTA)(H2O)2] and polynuclear Gd2-6L2-L6 complexes 

The [Gd(AAZTA)(H2O)2] chelate was used as a building block due to its remarkable properties: a) ease and high-yield synthesis, presence of two inner sphere water molecules in fast exchange with the bulk; b) high thermodynamic stability; c) kinetic inertness in the presence of physiological concentrations of CuII and ZnII higher than that of the clinical agent [Gd(DTPA)]2-; d) negligible tendency to formation of ternary complexes with endogenous anions. The study demonstrates that the strategy for relaxation enhancement varies with the strength of the magnetic field used.

Up to 3 T, efficacy is limited by molecular rotation and therefore increases proportionally with the increase in molecular size. Between 3 and 7 T, the issue of local flexibility or anisotropic rotation, evaluated with NMR techniques and computational models, becomes more and more relevant and medium-sized rigid systems (tri- or tetranuclear) provide the best results. At ultra-high fields (> 7 T), small and compact mono- or binuclear complexes are most effective (Figure 2).

 

Figure 2. Upper: T1-weighted phantom MR-images at 3 and 7 T on selected polynuclear complexes highlighting the effective signal enhancement of the new MRI probes at clinically relevant magnetic field strengths in comparison to the commercial MRI agent ProHance®. Lower: Signal enhancement (298 K) of Gd3L3, Gd4L4 and Gd6L6 compared to Prohance at 1, 3 and 7 T.

The results of this study allow identifying the most effective strategy for optimizing the CAs, each suited to a well-defined range of applied magnetic field strength.

 

Mauro Botta is full professor of Inorganic Chemistry in the Department of Sciences and Technological Innovation at the University of Eastern Piedmont (Italy). He received the “Laurea” cum laude in Chemistry at the University of Turin in 1985. His scientific interests have focused on the use of NMR techniques for the characterization of inorganic systems, starting from organometallic clusters and then moving on the complexes of the f-elements. Recipient of the “Raffaello Nasini” gold medal award for Inorganic Chemistry of the Italian Chemical Society and of the “GIDRM gold medal for magnetic resonance”. He has published over 280 papers (index H = 63; citation: 12800) and several book chapters on these topics and filed 5 patents.

 

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Tailoring MOFs and COFs for artificial photosynthesis

Over a couple of decades, solar-to-chemical energy conversion—so called “artificial photosynthesis”—has been regarded as a holy grail that enables a carbon-neutral production and use of fuels and chemicals. In principle, various kinds of chemicals can be produced using semiconducting materials or photosensitizers with a proper bandgap and band-edge positions for target redox reactions. Despite conceptual simplicity and elegance, the realization of artificial photosynthesis is a highly challenging task. Its realization requires not only the development of various functional components such as light-harvesting, charge separation/ transporting, and catalytically active materials, but also their rational and precise assembly into an integrated device. Conventional solar-to-chemical conversion devices are mainly composed of inorganic materials and suffer from low efficiency and poor stability issues. These issues originate from the intrinsic problems of conventional inorganic materials, such as low absorption coefficient, high recombination of charge carriers, low electrical conductivity, poor catalytic activity. Furthermore, they have limited flexibility in engineering their physicochemical properties compared to organic materials.

Figure 1. Solar-to-chemical energy conversion by (a) powder-type photocatalysts and (b) photoelectrochemical (PEC) cells.

On the other hand, porous reticular materials such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs) are recently drawing huge attention from researchers as promising functional materials. The structure and properties of MOFs and COFs can be tailored by employing various metal nodes and/or organic linkers, introducing additional functional groups, and employing different symmetry combinations, even with similar building blocks. These have led to the boom of studies about their design and synthesis for various applications such as catalysis, separation, sensing, etc.

Figure 2. Schematic illustration of the structure and properties of MOFs and COFs.

Recently, Prof. Jungki Ryu, Hyunwoo Kim, and Nayeong Kim at Ulsan National Institute of Science and Technology (UNIST) reported a comprehensive review paper especially about the application of MOFs and COFs in solar-to-chemical energy conversion. Porous structure and readily tunable physicochemical properties of MOFs and COFs can be highly beneficial to improve light absorption, charge separation, and access to reactants. As a result, they have been employed as diverse functional components for various target photo-reactions, such as hydrogen evolution reaction, oxygen evolution reaction, and CO2 reduction reaction. To help readers readily understand recent progress and challenges in the application of MOFs and COFs for solar-to-chemical energy conversion, they have organized more than 200 recent studies on the basis of their function and target reaction in chronological order. In addition, they reviewed the application of MOFs and COFs parallelly to provide insights for researchers. For example, one can find similar strategies employed for their application and also expect future research directions for relatively new COFs based on the research progress for MOFs. Lastly, they pointed out that further studies are required especially for the growth of MOF and COF thin films to make more significant research progress in the application of MOFs and COFs for artificial photosynthesis.

Jungki Ryu is an associate professor in the UNIST School of Energy and Chemical Engineering. He received his bachelor’s and PhD degrees in Materials Science and Engineering from Yonsei University in 2006 and Korea Advanced Institute of Science and Technology (KAIST) in 2011, respectively. Before joining UNIST in 2014, he had worked as a postdoctoral associate at the Massachusetts Institute of Technology for 3 years. He is currently interested in designing innovative electrochemical and photoelectrochemical devices inspired by nature for a sustainable future. Currently, he is the author of more than 50 articles indexed by SCI(E) and cited over 3,000 times with an H-index of 28.

Homepage: https://www.bioinspired-materials.com/

Twitter account: @bfml_unist, @jungki1981

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Inorganic Chemistry Frontiers 2020 Best Paper Prizes

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Inorganic Chemistry Frontiers 2020 Best Paper Prizes

From this year onwards, we would like to introduce the Inorganic Chemistry Frontiers Best Paper prizes which recognize the most outstanding papers published in the journal. After a selection process involving the Associate Editors, Editorial and Advisory Board members, we have chosen to award not only a best paper but also a runner-up and a best review.

Best Paper 

High performance single-molecule magnets, Orbach or Raman relaxation suppression?

Alejandro Castro-Alvarez, Yolimar Gil, Leonel Llanos and Daniel Aravena

Inorg. Chem. Front., 2020,7, 2478-2486
https://doi.org/10.1039/D0QI00487A

 

Corresponding author:

Daniel Aravena is Associate Professor at University of Santiago of Chile. He was born in 1985 in Linares, Chile and received his undergraduate degree in Chemistry at University of Chile in 2009. He obtained his M. Sc. (2011) and Ph. D. (2013) from University of Barcelona (Spain) under the direction of Prof. Eliseo Ruiz. After a postdoctoral stage at Max-Planck Institute for Chemical Energy Conversion (Mülheim an der Ruhr, Germany) with Prof. Frank Neese and Prof. Mihail Atanasov, he joined University of Santiago de Chile in 2015. D.A. research focus in the calculation of spectroscopic and magnetic properties of diverse inorganic systems, such as Single Molecule Magnets, guest responsive Metal-Organic Frameworks, molecular devices, photomagnetic and spin-crossover compounds.

Currently, he is involved in the development of new models to simulate magnetic relaxation and the ab initio description of spin-orbit effects for excited state dynamics of inorganic complexes.

ORCID: https://orcid.org/0000-0003-3140-4852

 

Best Paper Runner-up

High-efficiency photocatalytic water splitting by a N-doped porous g-C3N4 nanosheet polymer photocatalyst derived from urea and N,N-dimethylformamide

Feng Guo, Lijing Wang, Haoran Sun, Mingyang Li and Weilong Shi

Inorg. Chem. Front., 2020,7, 1770-1779
https://doi.org/10.1039/D0QI00117A

 

Corresponding author:

Weilong Shi got his PhD from Huazhong University of Science and Technology in China, did his Postdoctoral at Zhengzhou University and is a Lecturer at Jiangsu University of Science and Technology, a Member of Jiangsu Composites Society. His research interests include design, construction and modification of carbon-based (carbon dots, carbon nitride) nano-semiconductor composite photocatalytic materials, as well as photocatalytic degradation of organic pollutants in aquatic environment and water splitting into hydrogen under visible light. So far, a total of 42 papers were published by SCI first author or correspondence author, 13 ESI highly cited papers, 6 ESI hot papers, 1 Running Up Best Paper in Inorganic Chemistry Frontiers of 2020, H-index 29. He is now in charge of the National Natural Science Foundation of China, Jiangsu Province “mass entrepreneurship and innovation doctor” talent project, Henan Province postdoctoral research project and so on.

ORCID: https://orcid.org/0000-0002-3555-4543

 

Best Review

Recent advances in MOF-based photocatalysis: environmental remediation under visible light

Qi Wang, Qiaoyuan Gao, Abdullah M. Al-Enizi, Ayman Nafady and Shengqian Ma

Inorg. Chem. Front., 2020,7, 300-339
https://doi.org/10.1039/C9QI01120J

 

Corresponding authors:

Qi Wang obtained her Ph.D. degree in 2009 under the supervision of Prof. Jincai Zhao from the Institute of Chemistry, Chinese Academy of Science. She is currently a professor in the School of Environmental Science and Engineering at Zhejiang Gongshang University. She worked as a visiting scholar in the University of South Florida in 2019. Her research interests focus on photocatalysis, photoelectrocatalysis and environmental catalysis.

ORCID: https://orcid.org/0000-0002-1941-5287

Shengqian Ma obtained his B.S. degree from Jilin University, China in 2003, and graduated from Miami University (Ohio) with a Ph.D. degree in 2008. After finishing two-year Director’s Postdoctoral Fellowship at Argonne National Laboratory, he joined the Department of Chemistry at the University of South Florida (USF) as an Assistant Professor in August 2010. He was promoted to an Associate Professor with early tenure in 2015 and to a Full Professor in 2018. His current research interest focuses on the development of functional porous materials including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), and porous organic polymers (POPs) for energy, biology, and environment-related applications.

ORCID: https://orcid.org/0000-0002-1897-7069

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Copper catalysts for photo- and electro-catalytic hydrogen production

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The development of carbon neutral, or better still carbon zero (H2) future fuels with production driven by green energy (renewables, such as solar, wind or wave generated energy) is an urgent necessity. To be cost competitive, green production of hydrogen requires long lived, high activity catalysts made from inexpensive, earth abundant metal ions.

 

Over the last few decades, various earth-abundant molecular cobalt, iron and nickel catalysts have exhibited activity for HER under photo- and electro-catalytic conditions. Prior to this study only 15 molecular copper complexes had been tested as catalysts for the H2 evolving reaction (HER) under either photo or electro-catalytic conditions.

 

Recently, Abdullah Abudayyeh in the group of Sally Brooker at the University of Otago and collaborators Garry Hanan and Olivier Scott at the University of Montreal reported the results of testing three copper(II) complexes – with a range of geometries, from square planar 1 to square pyramidal 2 and trigonal bipyramidal 3 (Figure 1) – as catalysts for HER under both photo- and electro-catalytic conditions.

Figure 1.  Right: Square planar 1 (pink), square pyramidal 2 (red) and trigonal bipyramidal 3 (green) copper(II) complexes. Left: HER electrocatalysis data shows that only square planar([CuIILEt]BF4 is, or forms, a good electrocatalyst for HER, and that it is still active after 6 hours. Black line = control.

The research team showed that under photocatalytic conditions the 3 copper complexes have modest turnover numbers (TON=460-620), but the control, using Cu(BF4)2, had a higher TON (740), and the blank (no copper) also had significant activity (TONequiv=290). So this is a cautionary tale: whilst these complexes initially appeared to be promising catalysts for photocatalytic HER, running the control and blank – studies often not reported – shows otherwise.

 

Hence the team changed focus and tested all three copper complexes as HER electrocatalysts in MeCN/acetic acid solution (Figure 1). The macrocyclic square planar complex, [CuIILEt]BF4 (1) (Figure 1, pink), is shown to be, or to form, an effective and stable electrocatalyst for HER in MeCN with acetic acid as the proton source (TON = 12.5 over six hours at -1.6 V vs 0.01 M AgNO3/Ag; at 100 mVs-1, Ecat/2=-1.64 V so overpotential necessary for catalysis=0.23 V), whilst the other two complexes, 2 and 3, had activities similar that of the control.

 

Preliminary ‘rinse and repeat’ and ‘drop of Hg’ tests – for the formation of catalytically active heterogeneous deposit on the glassy carbon working electrode or nanoparticles, respectively – are consistent with homogeneous catalysis by 1. But the authors note that it is distinctly possible that these initial test results are ‘false negatives’ (they recommend reading the excellent review by J. Dempsey on this topic), as the CVs show a stripping process consistent with the deposition of metallic copper on the electrode, so it remains possible that a heterogeneous catalytically active species forms, but is not seen as it is unstable in air or falls off the electrode during the rinse step.

 

Future studies on 1 aim to determine whether the catalytically active species is homogeneous or heterogeneous, but regardless of the outcome, the observed HER performance is promising and long lived.

 

Left to right: Abdullah, Olivier, Humphrey, Garry and Sally

 

 

Abdullah M. Abudayyeh completed his BSc in Chemistry in Mu’tah University, Jordan. He received his MSc in organic chemistry from the University of Jordan, working on Schiff base amidine systems. On successful completion of his MSc he worked as a chemistry teacher at the United Nations secondary school in Jordan for five years and then in a couple of other schools in Jordan, before moving to the University of Bradford, UK, in 2015. There he pursued his second MSc degree, developing thin films of Zr-based metal-organic frameworks (MOFs) on a conductive FTO substrate, which he completed with distinction. He then moved to Dunedin, New Zealand, to take up a University of Otago PhD scholarship in Professor Sally Brooker’s research group, working on coordination complexes as catalysts for the hydrogen evolution reaction (HER).

 

Olivier Schott graduated with the Bachelor of Chemistry and two Masters: Supramolecular and Molecular Chemistry and Chemical Physics and Materials at Université de Strasbourg (France). His first steps in research with Professor Julve and Professor Kurmoo were related to the synthesis of supramolecular inorganic architectures for the study of magnetic exchange interactions between transition metals. During an international student exchange, he joined the Green Energy Group of Université de Montreal (Canada) under the direction of Professor Garry S. Hanan and became a PhD candidate. In the domain of molecular artificial photosynthesis, he is investigating various poly-metallic N-rich supramolecular systems for the photocatalysis of solar fuels. In 2019, he got a PhD fellowship: Fonds Québécois de la Recherche sur la Nature et les Technologies (FRQNT) and received three times the J. Armand Bombardier Excellence Award.

 

 

Humphrey L. C. Feltham obtained his MSc and PhD (both with distinction) in Chemistry from the University of Otago under the supervision of Professor Sally Brooker, working on tetrametallic 3d-4f macrocyclic Single Molecule Magnets. From 2012-2018 he was a research associate in Professor Brooker’s team, working on projects ranging from the tuning of spin crossover complexes to the covalent immobilisation of magnetically and catalytically interesting complexes onto Au nanoparticles and PEDOT films. In 2019, he joined the chemistry team at Ligar Limited Partnership (www.ligar.nz), developing novel polymers for the removal or recovery of valuable or unwanted molecules from a variety of solutions. eg. removing smoke taints from wine, recovering bioactive molecules from plant extracts, remediating toxins from drinking water, and modifying flavour of beverages.

 

Professor Garry S. Hanan received his Ph. D. degree from l’Université Louis Pasteur in Strasbourg, France, in 1995.  After working in at the Max-Plank Institut fuer Kohlenforschung (1996-1997) and l’Università di Messina (1997-1998) as a post-doctoral Fellow, he started his academic career at the University of Waterloo in 1998 (Assistant Professor). In 2002 he moved to the Université de Montréal (as Associate Professor) where he is currently a Full Professor.  He was recently awarded an Accelerator Grant and is currently the leader of a Strategic Project, both funded by the Natural Sciences and Engineering Research Council of Canada (NSERC).  His current research interests include metal-assembled complexes, inorganic photochemistry, and photocatalytic hydrogen production.

 

Professor Sally Brooker (MNZM, FRSNZ, FNZIC, FRSC) studied at the University of Canterbury, New Zealand [BSc(Hons) first class; PhD with Professor Vickie McKee]. After postdoctoral research at Georg-August-Universität Göttingen, Germany, with Professor George M. Sheldrick, she took up a Lectureship at the University of Otago where she is now a full Professor and Sesquicentennial Distinguished Chair. She has been the recipient of numerous awards, most recently including a 2017 Queens Birthday Honour for services to science (MNZM), the 2017 Hector Medal (RSNZ) and 2017 Burrows Award (RACI). Her research interests concern the design, synthesis and full characterisation of, primarily paramagnetic, di- and poly-metallic complexes of transition metal and lanthanide ions with polydentate acyclic and macrocyclic ligands, as these have interesting redox, magnetic, catalytic and photophysical properties (otago.ac.nz/brooker).

 

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Investigation on Nanostructured Cu Based Electrocatalysts for Improvising Water Splitting: A Review

By .

The effective use of earth abundant electrocatalyst copper in splitting of water as nanostructures with different combinations is central in replacing the noble metals for the industrialization of hydrogen generation. Being the carbonaceous fuels as front line suppliers of energy, they adversely lead to affect the environment with the greenhouse gases emission. Considering the electrocatalytic way of splitting water, it is one of the finest ways of producing pure hydrogen with fast rate and assisted with no other undesired by-products and hence researchers across the world focus maximum attention to make it commercially applicable.

To replace the noble metals, transition metals based catalysts are promising and the importance of Cu based nanostructures as effective electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) needs greater attention. Moreover, various synthetic approaches with Cu nanostructures like mono, bi and tri metallic catalysts as oxides hydroxides, sulfides, selenides, tellurides and phosphides were studied for OER and HER in different pH conditions will give a vast analysis on Cu based catalysts towards real scale water splitting electrocatalytically.

Hence, to precise, a brief understanding on Cu-based nanostructures in electrocatalytic water splitting is highly needed to be applied with other advancements in catalysts development for the viable hydrogen generation with electrocatalytic water splitting.

Recently, Karthick. K and Subrata Kundu and co-authors have highlighted the nanostructures of Cu based oxides, hydroxides, sulfides, selenides, tellurides and phosphides as catalysts for water splitting application and the merits of which have been explored in detail as a review. The possibilities of enhancing the activity and durability with Cu based catalysts were studied and among which enhancing the activity with the formation of nanostructures, growing over 3D conducting supports, enhancing the electrical conductivity with graphene, increasing the metallic active sites by different methods like electrodeposition, adding other transition metals and also by varying the stoichiometric ratios had resulted in ensuring astonishing activity and stability.

Figure 1. Cu nanostructures as catalysts for enabling high scale OER and HER activities by studying them as oxides, LDHs, chalcogenides and phosphides.

 

Authors:

K. Karthick

CSIR – Central Electrochemical Research Institute

K. Karthick had received his B.Sc degree from Government Arts and Science College, Udumalapet, India and M.Sc degree from The American College – Madurai, India in general chemistry. He qualified UGC-JRF in December-2014 and joined under Dr. Subrata Kundu’s research Group since August-2015. He is currently working towards his Ph.D thesis mainly focused on Electrocatalytic Water splitting applications.

https://scholar.google.co.in/citations?user=RU1m2ScAAAAJ&hl=en

Dr. Subrata Kundu

CSIR – Central Electrochemical Research Institute

Dr. Subrata Kundu received his Ph.D from the Indian Institute of Technology (IIT), Kharagpur, India in early 2005. Then he moved to University of Nebraska, Lincoln, USA and later to Texas A&M University, College station, Texas, USA as a post-doc fellow (from 2005 to 2010). He is currently working as a Senior Scientist at CSIR-CECRI, Karaikudi, India. Dr. Kundu is serving as an editorial board member of several international journals including prestigious ‘Scientific Reports’ from Nature publishers since 2015. Dr. Kundu and his co-workers are working in the forefront area of Material Sciences with emphasizes on energy, environment, catalysis and electrocatalysis.

https://scholar.google.co.in/citations?user=4siGGnQAAAAJ&hl=en

https://www.cecri.res.in/Profile?empcode=40257

https://anantharaj1402.wixsite.com/dr-sk-group

 

Article information:

Investigation on Nanostructured Cu Based Electrocatalysts for Improvising Water Splitting: A Review
Karthick Kannimuthu, K. Sangeetha, S. Sam Sankar, Arun Karmakar, Ragunath Madhu and Subrata Kundu
Inorg. Chem. Front., 2020, Accepted Manuscript
https://doi.org/10.1039/D0QI01060J

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