A new ɛ-Keggin polyoxometalate-based metal-organic framework: From design and synthesis to electrochemical hydrogen evolution

A new ɛ-Keggin polyoxometalate based metal-organic framework, [TBA]3[H4PMo8VMo4VIO40Zn4](HTPT)2 (1) (H3TPT = 1,1′:4′,1″-terphenyl-3,4″,5-tricarboxylic acid, TBA+ = tetrabutylammonium ion) was synthesized under hydrothermal conditions. The tetrahedral Zn4-ε-Keggin is connected through angular HTPT2− to form a 2D entangled structure with 2-fold interpenetration. The whole network displays a staggered layer structure in AB/CD/EF/GH/AB/CD/EF/GH arrangement with extensive hydrogen bonding and intermolecular interactions. More interestingly, compound 1 exhibited good hydrogen evolution reaction (HER) activity in an acidic medium, with a Tafel slope of 68 mV·dec−1 and an η10 of 417 mV. It showed an excellent long-term stability, which could maintain its catalytic activity after 1000 cycles.