Modulating Pt nanoparticles confined in UiO-66 by linker functional groups for controllable hydrogenation

Encapsulation of clean metal nanoparticles (NPs) into interior of metal-organic framework (MOF) is of great importance to remarkably improve the stability and tune the catalytic performance of metal NPs. Herein, highly dispersed Pt NPs are encapsulated in UiO-66 with different functional groups on linker (UiO-66-X, X=F, H, NH2, OH) through enhanced electron attraction of metal precursor by MOF node and proper reduction by H2/Ar gas. Compared with traditional impregnation method, the encapsulation method gives well-defined Pt NPs and controllable microenvironment. Detailed characterizations reveal that functional group of the linker can effectively tune the microenvironment and electronic properties of guest Pt NPs. In situ FTIR was utilized to investigate the adsorption capability and strength of reactants on the catalysts. The electron-deficient Pt species and appropriate surface hydrophobicity match well with the reactants, which is responsible for enhanced catalytic hydrogenation activity of C=C and nitro groups. The surface hydrophobicity plays a major role in promoting alkyne hydrogenation. This work is devoted to rationalize the relationship between hydrogenation performance and catalyst property of UiO-66 encapsulated Pt NPs, in terms of energy adaptability in electronic state and structure adaptability in surface chemistry. Rational design strategy of Pt-confined-in-MOF composites through molecular level regulation is provided for hydrogenation.