Amino group promoted photoelectrocatalytic CO 2 reduction activity observed in mixed-linker Cu-based metal–organic frameworks

The absorption of visible light of mixed-linker metal–organic frameworks can be enhanced by adding organic ligands to be present as reaction sites. In this work, through the introduction of an amino-functionalized organic ligand (NH 2 BDC, BDC = 1, 4-benzenedicarboxylate) into the structure of CuBDC, dual-ligand Cu-based MOF (CuBDC- x NH 2 /CF, x represents the molar ratio of NH 2 BDC) was successfully synthesized on copper foam (CF). The photoelectrocatalytic CO 2 reduction performance of all samples was explored when increasing amounts of NH 2 BDC linkers (0%, 5%, 10%, 20%, 50%, and 100%) are incorporated in the framework. The highest Faradaic efficiency of CO (51.5%) was achieved when the molar ratio of NH 2 BDC was 10%. NH 2 BDC can effectively improve the visible light absorption ability of MOFs. And both terephthalic acid (H 2 BDC) and NH 2 BDC are coordinated with Cu–O clusters, which contribute to the generation and separation of charges. At the same time, the amino functional group can effectively adsorb the CO 2 molecules as a basic site. The synergistic effect improves the Faradaic efficiency of the reduction products.