Copper-Modified Three-Dimensional Polyoxometalate-Based Metal–Organic Framework for Efficient Photocatalytic Hydrogen Production

Efficient and stable noble-metal-free photocatalysts are highly desirable for renewable energy. A three-dimensional polyoxometalate-based metal–organic framework (POMOF), [Cu I 2 Cu II 3 (ptzH) 6 (H 2 O) 2 (OH) 2 ] (SiW 12 O 40 ), was constructed as a photocatalyst through the self-assembly of multivalent copper nodes (Cu + /Cu 2+ ), 5-(2-pyridyl)-1 H -tetrazole organic ligands, and Keggin-type silicotungstate anions. Structural characterization confirmed a stable open framework with ordered nanochannels in Cu 5 -SiW 12 . Relative to pristine SiW 12, a reduced optical band gap (from 3.60 to 3.22 eV) and a negative shift of 0.49 V in the conduction band minimum were observed for Cu 5 -SiW 12 (from 0.14 to −0.35 V). Such property modifications are ascribed to the appreciable electronic coupling between copper centers and SiW 12 moieties, through which synergistic enhancements in light harvesting, charge separation, and charge transport efficiency are achieved. Under optimized reaction conditions, a hydrogen evolution reaction (HER) activity of 5190.89 μmol g –1 h –1 was attained for Cu 5 -SiW 12, representing a 19-fold enhancement over pristine SiW 12 and outperforming numerous reported noble-metal-free photocatalysts. Mechanistic studies attribute the superior performance to synergistic effects: an optimized band structure, framework-enabled charge separation, and in situ generated heteropoly blue (HPB). This study develops a photocatalyst with notable hydrogen evolution activity and provides a viable strategy for the rational design of efficient molecular-based photocatalysts.