Asymmetric Ligands of a Metal–Organic Framework on Enhanced Photocatalytic CO2 Reduction

• Published in: Inorganic chemistry Vol. 62; no. 39; pp. 15824 - 15828
• Main Authors: Li, Ke, Ge, Sulong, Wei, Xiaoqian, Zou, Weixin, Wang, Xiuwen, Qian, Qiuhui, Gao, Bin, Dong, Lin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02-10-2023
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c02272

Metal–organic frameworks (MOFs) have been studied extensively in the catalytic field. However, the role of ligands in catalysis has been less well investigated. Here, an asymmetric ligand photocatalytic strategy for CO2 reduction in MOFs is first proposed. MOF-303­(Al) with asymmetric ligands (pyrazolyldicarboxylic acid) exhibits synergistic catalytic effects. Specifically, pyrazoles participate in CO2 activation; i.e., pyrazole and μ2-OH form hydrogen bonds with CO2 to polarize CO bonds. Furthermore, the lowest unoccupied molecular orbital (LUMO; A pyrazole) and highest occupied molecular orbital (HOMO; B pyrazole) act as the electron donor and acceptor to spatially separate the excited electron–hole, with A and B pyrazoles for CO2 and H2O adsorption to avoid competition, respectively. Owing to its advantages, MOF-303-modified g-C3N4 achieves nonsacrificial and transition-metal-free photocatalytic CO2 reduction to CO of 16.19 μmol·g–1·h–1, significantly higher than that of g-C3N4. This work provides fresh insights into asymmetric ligands in photocatalytic CO2 reduction.