Linker Engineering of Sandwich‐Structured Metal–Organic Framework Composites for Optimized Photocatalytic H₂ Production

Abstract While the microenvironment around catalytic sites is recognized to be crucial in thermocatalysis, its roles in photocatalysis remain subtle. In this work, a series of sandwich‐structured metal–organic framework (MOF) composites, UiO‐66‐NH₂@Pt@UiO‐66‐X (X means functional groups), is rationally constructed for visible‐light photocatalytic H₂ production. By varying the ─X groups of the UiO‐66‐X shell, the microenvironment of the Pt sites and photosensitive UiO‐66‐NH₂ core can be simultaneously modulated. Significantly, the MOF composites with identical light absorption and Pt loading present distinctly different photocatalytic H₂ production rates, following the ─X group sequence of ─H > ─Br > ─NA (naphthalene) > ─OCH₃ > ─Cl > ─NO₂. UiO‐66‐NH₂@Pt@UiO‐66‐H demonstrates H₂ production rate up to 2708.2 µmol g⁻¹ h⁻¹, ≈222 times that of UiO‐66‐NH₂@Pt@UiO‐66‐NO₂. Mechanism investigations suggest that the variation of the ─X group can balance the charge separation of the UiO‐66‐NH₂ core and the proton reduction ability of Pt, leading to an optimal activity of UiO‐66‐NH₂@Pt@UiO‐66‐H at the equilibrium point.