Catalysis Science & Technology Blog

The latest themed issue from Catalysis Science and Technology, “Catalysis on Chiral Surfaces: From Fundamental Aspects to Application”, contains a plethora of articles reporting on the latest heterogeneous catalysts with significant stereospecific properties for asymmetric or chiral transformations.

In an article from the group of Dr Raja at the University of Southampton, UK, S. Newland et al. demonstrate the importance of anchoring organocatalysts to the inner walls of mesoporous silica to attain highly active and selective catalysts. Traditionally, organocatalysts are used in a homogeneous fashion, however this often leads to labour and energy intensive recollection for recycling of the catalyst. The covalent anchoring of cinchonine to the inner walls of mesoporous silicas not only gains the facile recycle benefits of a heterogeneous catalyst, but can increase the activity 6-fold for Michael addition reactions compared with the homogeneous analogue. And this is all achieved without sacrificing the enantioselectivity of the catalyst!

The anchoring methods were applied to DABCO, another molecule used as a chemoselective organocatalyst to show that the method could be applied to a variety of different catalysts with equally impressive results. It is easy to envisage these anchoring methods being significantly useful to any researchers working in the area of chiral organocatalysis.

Want to find out more on the synthesis and origin of these catalytic properties? Read the full article now!

Highly effective design strategy for the heterogenisation of chemo- and enantioselective organocatalysts
Stephanie H. Newland, David J. Xuereb, Enrica Gianotti, Leonardo Marchese, Ramon Rios and Robert Raja
Catal. Sci. Technol., 2015,5, 660-665, DOI: 10.1039/C4CY00895B,

Surely the next go-to article in the area of semiconductor photocatalysis, this thorough review by a group from the US is likely to appeal to both young researchers and established scientists alike. If you are new to the area of photocatalysis with semiconductor materials, the authors do a great job of collating the best background literature to introduce the topic, key principles and concepts in a concise fashion. At the same time, the authors have intricately organised the cutting edge research in the field so as to provide a useful tool for established researchers to continue pushing the frontiers of solar energy conversion.

In the first instance, a summary of single material photocatalysts are discussed from the well-known metal oxides and sulphides such as TiO₂ and CdS through to mixed metal oxides and heavier group VI materials. Especially highlighted is how the chemical and physical structures of materials help to define the optical properties that are required for catalytic processes; band structures can be influenced by doping and energy losses can be minimised by manipulating the dimensionality and macrostructures of engineered materials.

Further discussed are more complex semiconductor composites, bringing together multiple semiconductors or combining with other materials such as carbons. These in turn have led to the development of devices such as tandem cells, which have drastically improved upon the quantum efficiencies that can be attained. The authors have successfully drawn together state-of-the-art work, breaking down the theoretical considerations in a logical manner, to allow the reader to appreciate the current state of research in the field whilst leaving the door wide open for development and innovation for the future.

Take a look at the full review article now!

Semiconductor-based photocatalysts and photoelectrochemical cells for solar fuel generation: a review

Jiangtian Li and   Nianqiang Wu

In this recent communication, W. Zhang and co-workers have demonstrated a novel way to form covalent porphyrinic frameworks (CPFs) using squaraine and hydrazine linkers. By using purely organic moieties the researchers have eliminated the need for metal nodes that are present in the more traditional porous coordination polymers.

Using the principles of supramolecular chemistry the authors have used a metallation process to introduce manganese, a well-known and abundant redox active transition metal, into the cavity of the porphyrin component of the framework. Thus, an easily accessible active site for redox catalysis was generated and subsequently demonstrated to be active for the selective oxidation of aliphatic molecules.

Interestingly, it was also shown that the choice of linker can have an effect on the resulting catalytic activity of these new materials. Preliminary characterisation showed a correlation between the extended conjugation of the organic framework, the state of the manganese and the activity/selectivity of the catalytic processes. This phenomenon, often observed in homogeneous porphyrin catalysts, has been elegantly incorporated into these heterogeneous analogues. One can hypothesise that in future, by careful design of the organic linkers joining the porphyrin units, it may be possible to fine-tune the material for different catalytic reactions.

To find out more, why not take a look at the article now?

Bottom-up approach to engineer two covalent porphyrinic frameworks as effective catalysts for selective oxidation

Weijie Zhang, Pingping Jiang, Ying Wang, Jian Zhang and Pingbo Zhang

Catal. Sci. Technol., 2015, DOI: 10.1039/C4CY00969J