From zeozymes to bio-inspired heterogeneous solids: Evolution of design strategies for sustainable catalysis

Bio-derived transition-metal complexes containing well-defined and well-characterized active sites can be anchored, in a site-isolated fashion, on to the inner walls of porous inorganic supports, for generating highly active and selective single-site heterogeneous catalysts, which can serve as effective functional mimics of metalloenzymes. The nature of an active site in an enzyme and its ability to harness a particular catalytic function with remarkable selectivity, via its protein tertiary structure, could be judiciously transposed to zeolitic architectures with specifically engineered active sites. Throughout this article we follow the progress and evolution of engineering enzymatic activity and selectivity in synthetically designed catalysts, emphasizing the importance and the advantages of the different synthesis methodologies in immobilizing bio-inspired catalytically active single-sites on varying solid supports. The benefits of such systems are highlighted in terms of their environmental impact by reduction of waste, mitigating the generation of greenhouse gases, boosting the enantioselectivity in heterogeneously catalyzed reactions and in the utilization of 'greener' oxidants; with conclusions drawn on how specific supports affect catalytic properties via modification of the local environment of the active site. The seminal contributions of Dr. Ratnasamy in this field have paved the way for a more fundamental understanding of how the support environment, and its interactions with the active site at a molecular level, can lead to development of structure-activity relationships, which in the future can provide avenues for specifically tailoring catalytic outcomes from a mechanistic standpoint. (C) 2012 Elsevier B. V. All rights reserved.