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

Direct photoconversion of low-concentration CO into a widely tunable syngas (i.e., CO/H mixture) provides a feasible outlet for the high value-added utilization of anthropogenic CO . However, in the low-concentration CO photoreduction system, it remains a huge challenge to screen appropriate catalysts for efficient CO and H production, respectively, and provide a facile parameter to tune the CO/H ratio in a wide range. Herein, by engineering the metal sites on the covalent organic frameworks matrix, low-concentration CO can be efficiently photoconverted into tunable syngas, whose CO/H 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 evolution sites due to the much stronger binding affinity to H O, while Ni sites act as the CO production sites for the higher affinity to CO . 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 photoreduction and providing a modular design strategy for syngas production.