The Synergy of Cocatalysts and Covalent Organic Frameworks for Hydrogen Evolution

Abstract

Hydrogen, thefuture green fuel, has gathered special attentionin the field of energy research owing to its high energy density andclean characteristics. In recent times, covalent organic frameworks(COFs) have shown potential as promising H-2 evolution catalyst.This review discuss the advancement of COF and cocatalysts based photo-,electro- and photoelectrochemical H-2 evolution catalyticsystems and highlights their synergetic behavior. Hydrogen (H-2), the next-generation green fuel,can beobtained by the catalytic splitting of water using solar and electrochemicalmethods and a combination of both (photoelectrochemical). Among thevarious porous catalytic water reduction systems developed, covalentorganic frameworks (COFs) based systems are emerging in recent timesdue to their structural ordering and facile tunability, high thermo-chemicalstability, and permanent porosity. This review provides a detailedsummary and analysis of COF-based photo-, electro-, and photoelectrochemicalhydrogen evolution systems. Uniquely, it includes the journey fromprecious noble metal to earth-abundant molecular cocatalysts for thegeneration of H-2 and their synergetic interaction withCOFs. Moreover, the focus is on outlining the core concept of heterogeneouscatalytic H-2 evolution, measurement techniques, photophysicaland physicochemical insights, and the relationship among key componentsof the overall process. Finally, the advantages and pitfalls of COFsas H-2 evolution systems and the design principles for optimalcatalytic efficiency are discussed. A dedicated outlook section ispresented at the end to benefit researchers for future developmentsin this emerging field.