Metal-organic framework-coupled ZnIn₂S₄ for boosting photocatalytic hydrogen evolution

Metal-organic frameworks (MOFs) have attracted tremendous interest in the photocatalytic hydrogen evolution reaction (HER). Nevertheless, their practical catalytic performance is limited by the rapid recombination of photogenerated charge carriers and sluggish interfacial reaction kinetics. Herein, a hierarchically structured UiO-66-NH₂(Hf) / ZnIn₂S₄ (denoted UN-66/ZIS) heterostructure was rationally fabricated via a solvothermal strategy to simultaneously regulate charge separation efficiency and optimize interfacial catalytic kinetics. Benefiting from the intimate heterointerface and built-in electric field, the optimized UN-66/ZIS sample exhibits remarkably improved visible-light absorption capability and charge transport efficiency, achieving a photocatalytic hydrogen production of 6052 ± 206 μmol·g^-1, which greatly outperforms pristine UN-66 and ZIS. More importantly, in-situ X-ray photoelectron spectroscopy combined with density functional theory calculations directly unveils the mechanism of interfacial charge redistribution and directional electron transfer responsible for the enhanced carrier separation efficiency, offering mechanistic insights into the improved catalytic activity. Furthermore, loading of Pt cocatalyst effectively accelerates the surface hydrogen evolution kinetics. The corresponding hydrogen evolution rate increases to 14,403 ± 287 μmol·g^-1·h^-1, approximately seven times that of the Pt-free heterostructure. This work proposes a synergistic strategy integrating heterojunction engineering and cocatalyst modulation to simultaneously optimize light harvesting, charge separation and surface reaction kinetics, which provides new guidelines for the rational design of high-performance MOF/sulfide photocatalysts toward solar hydrogen production.