Adjust the MIL-125-NH2 microenvironment via regulation of Pd valence states to accelerate electron transfer for promoting photocatalytic hydrogen evolution

Abstract

Nowadays, heterogeneous catalysis plays an increasingly important role in industry. However, the traditional heterogeneous catalysts still have some shortcomings in fine structure, such as lack of customization and difficulty in regulation. The multifunction and adjustability of metal-organic framework materials (MOFs) make it easier to realize the customized design of microenvironment, so they have extensive application potential in heterogeneous catalysis reactions. In this article, we obtained a mixed ligand NM-125-PdTCPP by grafting PdTCPP in MIL-125-NH2 for photocatalytic hydrogen evolution. In addition, we reduced a certain amount of PdⅡ in PdTCPP to Pd0 species through different reduction time in a hydrogen atmosphere, achieving changes in the valence states of guest co-catalysts within the host framework of MIL-125-NH2, and further regulating the influence of changes in the valence microenvironment on the photocatalytic hydrogen evolution performance. The catalyst with a reduction time of 1 hour (abbreviated as Pd(1 h)@NM-125) has the best photocatalytic hydrogen evolution effect, reaching 603 μmol g−1·h−1, which is 8.5 times as that of the original sample. This study provided a feasible idea for the regulation of MOFs' microenvironment to adjust the photocatalytic performance.