No 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.