Crystal Facet‐Dependent Photocatalytic Hydrogen Evolution From Ultra‐Stable Cu‐Zr/Hf Heterobimetallic Metal–Organic Frameworks

Solar-driven water splitting for hydrogen production over metal-organic frameworks (MOFs) is particularly attractive yet remains a challenge. Here, we report a series of ultra-stable heterobimetallic MOFs (M-BCA-M', M = Cu⁺, M' = Zr⁴⁺ or Hf⁴⁺) for photocatalytic hydrogen production, in which, the Cu(I) species act as the active center, whereas Zr(IV)/Hf(IV) plays an essential role in stabilizing the framework. Uniform MOF crystals with distinct morphologies were obtained, showing a rare crystal facet-dependent photocatalytic behavior. The octahedral MOF crystals denoted as Cu-BCA-Hf-O with the exposure of only {101} and {011} facets exhibit a record-high hydrogen production rate (49825.71 µmol g^-1 h^-1) among pristine MOF photocatalysts. The exceptional performance of Cu-BCA-Hf-O can be primarily attributed to its superior photogenerated carrier transfer ability and abundant active sites exposed on the crystal surface. This study provides molecular-level insights into the coordination regulation and morphology control of MOFs for highly efficient photocatalysis, highlighting the promising future of pristine MOF photocatalysts.