Journal of Materials Chemistry Blog

This Feature Article by Jose Manuel Valverde from the University of Seville, reviews Ca-based adsorbents for post-combustion carbon capture in Ca-looping processes. This process involves the carbonation reaction of CaO to capture CO₂, followed by calcination of limestone to regenerate the sorbent. The author discusses several topics, including: strategies for reactivation of natural limestones, Ca-based sorbents from synthetic precursors, the use of nanomaterials, the performance of sorbents under harsh calcination conditions, SO₂/CO₂ capture efficiency and physical methods to enhance CO₂ capture performance.

(Featured on the inside front cover of Issue 3 of J. Mater. Chem. A)

Ca-based synthetic materials with enhanced CO₂ capture efficiency
J. Mater. Chem. A, 2013, 1, 447-468.  DOI: 10.1039/c2ta00096b (free to read for a short time)

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Nonviral vector-based delivery of genetic information into cells to manipulate their protein expression is of great interest for applications in regenerative medicine and the treatment of genetic diseases. Nanoparticles are a type of nonviral delivery vehicle that can be employed; however their contact with cells is, too a large extent, a diffusion limited process. Using magnetic forces to pull magnetic nanoparticles towards target cells is an established technique to overcome this. However, this can have the drawback that the nanoparticles form overly tight complexes with DNA, which can inhibit gene release. Stimuli-responsive polymer vectors can be used to tune DNA unpacking, by adapting to microenvironmental changes such as temperature, pH, light and redox.

In this hot paper, scientists from Tianjin University describe the preparation of magnetic/thermoresponsive nonviral vectors in the form of monodispersed magnetic nanoparticles (MNPs). The authors investigate the physicochemical properties of the MNP-polymer brushes/DNA nanocomplexes and the in vitro gene transfection of the MNPs-polymer brushes under a magnetic field with variable temperature conditions. Co-application of magnetic field and temperature stimuli was shown to enhance gene transfection efficiencies.

Combining magnetic field/temperature dual stimuli to significantly enhance gene transfection of nonviral vectors
J. Mater. Chem. B , 2013,1, 43-51.  DOI: 10.1039/c2tb00203e (free to read for a short time)

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Metal-organic frameworks (MOFs) are a class of well-known crystalline compounds at the bridge of organic and inorganic chemistry. MOFs have many potential applications such as in gas storage and catalysis. They also have potential applications as semiconductors in photovoltaics, photo-emitters and transistors.

In this hot paper, researchers from the University of Bath, UK use DFT calculations to predict novel hybrid MOFs with desirable semiconductor properties. They expand on the ubiquitous II-VI and IV-VI semiconductors (e.g. CdS, ZnSe, PbTe) and investigate their corresponding hybrid organic-inorganic analogues based on the archetype 3D framework of Pb₃(C₆S₆). Five hybrids were found to be of interest because they have a negative formation enthalpy and band gaps predicted to be in the visible light spectrum. Thus, these five hybrids may have applications as photo-active materials.

Thermodynamic and electronic properties of tunable II–VI and IV–VI semiconductor based metal–organic frameworks from computational chemistry

J. Mater. Chem. C, 2013, Advance Article.  DOI: 10.1039/c2tc00108j (free to read for a short time)

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Acetylene is widely known for its use as a fuel in welding equipment and it is also a very important building block in industrial chemical synthesis. Unfortunately, obtaining high-purity acetylene is not a trivial matter. Removing methane and carbon dioxide via cryogenic distillation is extremely energy intensive due to the low temperature required and therefore a process that avoids the need for such cooling is extremely attractive.

Hui Xu et al. have recently demonstrated the effective purification of acetylene at room temperature and pressure through the use of a microporous metal-organic framework, Cu₆(PDC)₆ ^. 2.6H₂O (PDC = 3,4-pyridine-dicarboxylate). Known as UTSA-50, the material was designed such that its pores are not only optimally sized for gas storage but that they also contain both exposed metal atoms and pyridyl groups. This enables both electrostatic and hydrogen-bonding interactions with acetylene. The latter are thought to be the key to selectivity given the ability of pyridyl nitrogen atoms to form hydrogen bonds with acetylene but not with CO₂ or CH₄.

At 296 K and 1 atm the UTSA-50 framework can adsorb 91 cm^-1 g^-1 acetylene which is comparable to other materials with similar pore size and surface area. Henry’s law selectivities of 68.0 and 13.3 for acetylene over carbon dioxide and methane, respectively, are extremely promising. In fact, the selectivity for CO₂ is, according to the authors, the highest ever reported.

A microporous metal-organic framework with both open metal and Lewis basic pyridyl sites for highly selective C₂H₂/CH₄ and C₂H₂/CO₂ gas separation at room temperature

J. Mater. Chem. A, 2013, 2, 77.  DOI: 10.1039/c2ta00155a

James Serginson is a guest web writer for the Journal of Materials Chemistry blog. He currently works at Imperial College London carrying out research into nanocomposites.

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This Feature Article by McNeill and Ade reviews the characterisation of the structural composition and morphology of thin film organic semiconductors using different X-ray techniques. The authors discuss six different applications of soft X-rays including scanning transmission X-ray microscopy (STXM); resonant X-ray scattering; resonant X-ray reflectivity; near-edge X-ray absorption fine-structure spectroscopy; polarized STXM and polarized soft X-ray scattering. The authors conclude that soft X-ray techniques have great potential for unravelling the complex structures shown by organic semiconductor blends and multilayers.

Soft X-ray characterisation of organic semiconductor films
J. Mater. Chem. C, 2013, Advance Article.  DOI: 10.1039/c2tc00001f (free to read for a short time)

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