A Versatile Heterometallic Microporous MOF for Photocatalytic Hydrogen Generation.

Photocatalytic particulate systems offer a cost-effective solar hydrogen production but are generally limited by narrow visiblelight absorption and poor stability. Here, we report a family of heterometallic MOF, MIP215(ZrIV/MII) (MII  =  Cu, Ni), constructed from 8-connected Zr6 oxoclusters and 4-connected pyrazolate-carboxylate metalloligands using a onepot, ambient, water only synthesis. The resulting 4,8-connected scu frameworks feature one-dimensional microporous channels, chemical robustness in aqueous and organic media, and reversible solvent-responsive flexibility upon dehydration/rehydration. Both Cu or Ni based solids exhibit broad visible absorption range up to ca. 800 nm, and suitable band-edge positions for H2 evolution in water/methanol under simulated sunlight. In the absence of any cocatalyst, MIP215(Zr/Cu) delivers sustained activity exceeding 1 mmol·g- 1 H2 in 5 h, while MIP215(Zr/Ni) displays higher initial rates but reduced stability, in line with observed metalleaching and crystallinity loss. Time-dependent density functional theory calculations indicate that ligand-to-metal charge-transfer states localized on the metalloligands govern the photocatalytic response, underscoring the role of photophysics beyond thermodynamic driving force in the superior Cu-based performance. This work establishes a green and scalable approach to robust, flexible heterometallic MOFs with tunable photoactivity for efficient, noblemetalfree solar hydrogen production.