Tailoring Co Coordination Mode in COF Nanosheets for Efficient Solar-Driven Reduction of Non-Neat CO into Syngas.

Photocatalytic conversion of CO into syngas is a promising approach to solving energy and environmental challenges. However, the current studies are mainly conducted by using neat CO where CO enrichment and purification is an energy-intensive process. Herein, we report a Co-COOH-COF with an asymmetric tridentate ligand for syngas synthesis from different contents of CO. The nanosheets of the resulting champion catalyst, Co-COOH-COF enable an outstanding syngas production rate of 151.1 mmol g h from neat CO and 180.5 mmol g h from 40 vol% CO under visible light, while it is up to 112.3 mmol g h from neat CO and 116.0 mmol g h from 40 vol% CO under natural sunlight, which surpasses most of the previously reported state-of-the-art photocatalysts. Impressively, the catalyst also exhibits a widely and continuously adjustable CO/H molar ratio from 4:1 to 1:21. Experimental and theoretical studies indicate that the asymmetric tridentate ligand with carboxyl groups increases Co loading in the covalent organic frame (COF) by the formation of atomically dispersed N-Co-O sites and enhances dissociation of water and CO adsorption by hydrogen bonding, thus facilitating CO transformation and hydrogen evolution. This work presents a new pathway for the design of high-performance catalysts for the photoreduction of CO to syngas.