Rational Design of FeNi Bimetal Modified Covalent Organic Frameworks for Photoconversion of Anthropogenic CO2 into Widely Tunable Syngas

Direct photoconversion of low‐concentration CO₂ into a widely tunable syngas (i.e., CO/H₂ mixture) provides a feasible outlet for the high value‐added utilization of anthropogenic CO₂. However, in the low‐concentration CO₂ photoreduction system, it remains a huge challenge to screen appropriate catalysts for efficient CO and H₂ production, respectively, and provide a facile parameter to tune the CO/H₂ ratio in a wide range. Herein, by engineering the metal sites on the covalent organic frameworks matrix, low‐concentration CO₂ can be efficiently photoconverted into tunable syngas, whose CO/H₂ ratio (1:19–9:1) is obviously wider than reported systems. Experiments and density functional theory calculations indicate that Fe sites serve as the H₂ evolution sites due to the much stronger binding affinity to H₂O, while Ni sites act as the CO production sites for the higher affinity to CO₂. Notably, the widely tunable syngas can also be produced over other Fe/Ni‐based bimetal catalysts, regardless of their structures and supporting materials, confirming the significant role of the metal sites in regulating the selectivity of CO₂ photoreduction and providing a modular design strategy for syngas production.