Rational Design of FeNi Bimetal Modified Covalent Organic Frameworks for Photoconversion of Anthropogenic CO 2 into Widely Tunable Syngas

Direct photoconversion of low‐concentration CO 2 into a widely tunable syngas (i.e., CO/H 2 mixture) provides a feasible outlet for the high value‐added utilization of anthropogenic CO 2 . However, in the low‐concentration CO 2 photoreduction system, it remains a huge challenge to screen appropriate catalysts for efficient CO and H 2 production, respectively, and provide a facile parameter to tune the CO/H 2 ratio in a wide range. Herein, by engineering the metal sites on the covalent organic frameworks matrix, low‐concentration CO 2 can be efficiently photoconverted into tunable syngas, whose CO/H 2 ratio (1:19–9:1) is obviously wider than reported systems. Experiments and density functional theory calculations indicate that Fe sites serve as the H 2 evolution sites due to the much stronger binding affinity to H 2 O, while Ni sites act as the CO production sites for the higher affinity to CO 2 . 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 CO 2 photoreduction and providing a modular design strategy for syngas production.