Water-Stable Nickel Metal–Organic Framework Nanobelts for Cocatalyst-Free Photocatalytic Water Splitting to Produce Hydrogen

Development of water-stable metal-organic frameworks (MOFs) for promising visible-light-driven photocatalytic water splitting is highly desirable but still challenging. Here we report a novel p-type nickel-based MOF single crystal (Ni-TBAPy-SC) and its exfoliated nanobelts (Ni-TBAPy-NB) that can bear a wide range of pH environment in aqueous solution. Both experimental and theoretical results indicate a feasible electron transfer from the H₄TBAPy ligand (light-harvesting center) to the Ni-O cluster node (catalytic center), on which water splitting to produce hydrogen can be efficiently driven free of cocatalyst. Compared to the single crystal, the exfoliated two-dimensional (2D) nanobelts show more efficient charge separation due to its shortened charge transfer distance and remarkably enhanced active surface areas, resulting in 164 times of promoted water reduction activity. The optimal H₂ evolution rate on the nanobelt reaches 98 μmol h^-1 (ca. 5 mmol h^-1 g^-1) showing benchmarked apparent quantum efficiency (AQE) of 8.0% at 420 nm among water-stable MOFs photocatalysts.