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

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 H-2 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 H-2 production rates, following the X group sequence of H > Br > NA (naphthalene) > OCH3 > Cl > NO2. UiO-66-NH2@Pt@UiO-66-H demonstrates H-2 production rate up to 2708.2 & mu;mol g(-1) h(-1), & AP;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.