Self-assembly of a cobalt(II)-based metal-organic framework as an effective water-splitting heterogeneous catalyst for light-driven hydrogen production.

The solar photocatalysis of water splitting represents a significant branch of enzymatic simulation by efficient chemical conversion and the generation of hydrogen as green energy provides a feasible way for the replacement of fossil fuels to solve energy and environmental issues. We report herein the self-assembly of a Co-based metal-organic framework (MOF) constructed from 4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetrabenzoic acid [or tetrakis(4-carboxyphenyl)ethylene, HTCPE] and 4,4'-bipyridyl (bpy) as four-point- and two-point-connected nodes, respectively. This material, namely, poly[(μ-4,4'-bipyridyl)[μ-4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetrabenzoato]cobalt(II)], [Co(CHO)(CHN)], crystallized as dark-red block-shaped crystals with high crystallinity and was fully characterized by single-crystal X-ray diffraction, PXRD, IR, solid-state UV-Vis and cyclic voltammetry (CV) measurements. The redox-active Co atoms in the structure could be used as the catalytic sites for hydrogen production via water splitting. The application of this new MOF as a heterogeneous catalyst for light-driven H production has been explored in a three-component system with fluorescein as photosensitizer and trimethylamine as the sacrificial electron donor, and the initial volume of H production is about 360 µmol after 12 h irradiation.