A Review on Covalent Organic Frameworks: Exploration of Their Growing Potential as Porous Materials in Photocatalytic Applications

Photocatalysis powered by unlimited solar energy is an effective strategy to resolve energy and environmental issues. To achieve an efficient photocatalytic system, photocatalysts need to be highly crystalline and porous with excellent photostability under extreme conditions. Covalent organic framework (COF) has shown immense potential for photocatalytic application due to its unique structure, electronic, and photophysical characteristics. COF possesses a crystalline porous network with light absorption capabilities and excellent stability. Functionalized COFs can be developed through organic unit variation to obtain broader absorption, narrow bandgap, effective charge separation, and transportation. Furthermore, high photocatalytic efficiency can be achieved by heterostructure formation through anchoring or post-synthetic modification. Our review is focused on the recent advancement of COF as photocatalysts for various photocatalytic applications. The exploration commences by emphasizing the topological design, linkage chemistry, and functionalization of COFs, underscoring principles and requirements for high photocatalytic efficiency. It provides a deep dive into COF capabilities in different photocatalytic applications, covering areas such as hydrogen and oxygen evolution, carbon dioxide reduction, organic transformation, and organic pollutant degradation. Finally, it summarizes the pivotal points that need demanding attention and outlines future avenues, to offer fresh perspectives and contribute to revolutionary innovations in this rapidly evolving field.