Covalent Organic Framework: An Emerging Catalyst for Renewable Ammonia Production

Ammonia (NH3), a fertilizer feedstock and clean energy carrier, is produced primarily by the Haber‐Bosch method, which is environmentally hazardous and energy intensive. Therefore, there is an immediate need for a benign alternative, like catalytic nitrogen fixation, such as catalytic nitrogen reduction reaction (NRR). NRR must involve active, selective, scalable, and long‐lived catalysts to become a sustainable source of ammonia production. Recently, covalent organic frameworks (COFs) and COF‐based functional materials have been proposed as promising catalysts for NRR. COFs comprise repeating units of organic molecules connected by strong covalent bonds. By fine‐tuning the building blocks, various COFs can be designed with numerous active sites. This class of materials offers excellent modularity, porosity, stability, and low density. A novel type of nitrogen‐abundant COFs called covalent triazine framework (CTF) has been noted for its high electron density and ultra‐stability. This review examines the state‐of‐the‐art for the NRR using different COF‐based catalysts and discusses design principles for advancing it. The underlying mechanism of NRR with different strategies adopted for renewable ammonia production is also discussed for a clear understanding of the process. Furthermore, key parameters for improving ammonia synthesis‘s photo/electrocatalytic efficiency will also be highlighted to present new possibilities to this emerging field. Covalent organic frameworks (COFs) and COF‐based functional materials have been proposed as promising catalysts for nitrogen reduction reactions (NRR). Using COF‐based catalysts, three NRR strategies – photocatalytic (PNRR), electrocatalytic (ENRR), and photo‐electrocatalytic (PENRR) – can accomplish sustainable ammonia production.