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.