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Unifying Concepts in Catalysis

2010; Wiley; Volume: 2; Issue: 7 Linguagem: Inglês

10.1002/cctc.201000200

1867-3899

Christian Limberg, Matthias Drieß,

Surface Chemistry and Catalysis

1 A catalyst, by definition, is a substance that promotes the conversion of chemical starting materials into desired products without itself being changed or consumed. Imagine how our materials world, environment, quality of life, and current society would be without catalysis. While hard to imagine, it′s fairly certain that our life would be a disaster. How could we cope with the unavoidable global challenges resulting from the forthcoming shortage of natural resources, bearing in mind the drastically increasing material and energy needs, especially in developing societies? This immediately raises several important questions; how to substitute fossil resources such as crude oil by renewable sources with a sustainable energy supply or how to accelerate the development for syntheses of novel pharmaceuticals, such as antibiotics. As we look to the future, catalysis research will play a more important role than ever before. The necessity to improve our efficiency in exploiting natural resources calls for the development of tailor-made catalysts with novel, advanced properties and their subsequent integration into improved or newly designed production strategies. Likewise, efforts to improve our current understanding of catalysts on the molecular level are needed for a design of knowledge-based and predictive catalytic systems. The latter point in particular, the predictive design of catalysts, is very demanding because the complexity of catalysts is enormously manifold ranging from a single atom in a suitable environment (“single active site”) to molecular compounds and clusters of atoms adsorbed on complex solid surfaces to complex active sites embedded in protein matrices. Accordingly, active sites can be subdivided into three different types, designated as homogeneous, heterogeneous, and biological catalysts. Their structural and mechanistic investigation requires dedicated methodologies, which are adapted to the specific problems individually for each type, and hence, the different branches of catalysis have developed largely independently of each other. Moreover, the technical use of these systems requires the availability of highly specialized know-how in different branches of science and engineering, which explains the diversification of catalysis research over a large range of fields. Combining these traditional features of catalysis could provide an understanding of processes on different scales and thus establish a basis for catalyst design in the future. To benefit much faster from progress made in the different fields of catalysis and to achieve maximum synergy, it is highly desirable to combine, integrate, verify, and exploit the various views of catalysis communities. For this purpose, the Cluster of Excellence “Unifying Concepts in Catalysis” (UniCat, http://www.unicat.tu-berlin.de/) was founded within the Berlin area at the end of 2007 within the framework of the Excellence Initiative by the German federal and state governments, funded by the Deutsche Forschungsgemeinschaft. Catalysis research is powerful in the Berlin area, gathering expertise in heterogeneous, homogeneous, and biological catalysis as well as in engineering. In fact, UniCat is the largest consortium among the existing research clusters within the German Excellence Initiative consisting of six academic institutions in Berlin and Potsdam, namely the Technische Universität Berlin, the Humboldt Universität zu Berlin, the Freie Universität Berlin, the Universität Potsdam, the Fritz Haber Institute of the Max Planck Society, and the Max Planck Institute of Colloids and Interfaces. In a manner closely related to the philosophy of this journal, the initiative involves a team of researchers from various disciplines in chemistry, biology, physics, and engineering, and aims at integrating the different fields of catalysis in an effort to identify fundamental concepts, which provide a microscopic understanding of the processes, paving the way to new catalysts by knowledge-based approaches. UniCat’s research program is divided into three cross-linked research areas: A) “Bridging the Materials Gap in Complex Catalysis”; B) “‘Intelligent’ Natural and Artificial Enzymes”; C) “Complex Reaction Engineering” (see the Supporting Information for details). All three research areas are closely linked by topical interactions devoted to specific targets, such as methane activation, creating research bands and thereby going beyond the frontiers of classical catalysis research. This interdisciplinary approach may be exemplified by the oxidative coupling of methane (OCM) to produce ethene and water, a process important for current and future energy technologies, as it brings about the conversion of methane (i.e. natural gas) into value-added products. Knowledge about structure–property relationships gained from model systems, for example, suitable metal oxide clusters, powders, and films, in research area A constitutes a promising basis for the development of novel materials, such as those based on rationally designed precursors, with improved catalytic performance. These catalysts are then used in area C for scale-up to pilot plant level, in order to assess their reliability for industrial applications that necessitate the development a skilful combination of reactor and separation technology. Needless to say, this and related target-oriented research for the sustainable use of resources is done in cooperation with industrial laboratories. Examples of interdisciplinary research in area B include enzyme-sensor complexes, which allow for the triggering of catalytic processes, in vitro and in vivo, by external stimuli, as well as the elucidation of oxygen-tolerant [NiFe] hydrogenases and their use as hydrogenase–photosystem hybrids for light-driven biotechnological hydrogen production in area C. This particular target is part of a rapidly emerging field of research reflected by recently launched international initiatives, such as the Solar Hydrogen program of the EU, or the BioSolarH2 program in the US. Other exciting examples of ongoing targeted research, emphasizing the fruitful impact of cooperation between scientists from different laboratories and disciplines, could be expressed here; some such examples from the UniCat cluster are represented in this Special Issue of ChemCatChem, which also includes several invited guest contributions that complement our line of argument and the philosophy of UniCat. After merely two and a half years of UniCat research, it is already visible that the initiative has led to much faster progress through synergisms than would have been possible within the individual branches of catalysis. Likewise, unforeseen exciting new results have been achieved, ranging from materials synthesis for solar-energy-driven catalytic transformations, novel molecular catalysts for facile activation of small molecules, heterogenization of homogeneous catalysts, structuring of surface nanoparticles, structural elucidation of metalloenzyme cofactors, and process modeling to the use of new reactor types. Obviously, this Special Issue contains only some results of the cluster’s work, while many other publications have appeared elsewhere (selected references are provided in the Supporting Information). The guest editors would like to thank all of those who have contributed to this Special Issue, and the editorial office of ChemCatChem for its kind assistance.1