The Synthesis And Catalytic Evaluation Of Pd@MOFs

Metal-organic frameworks （MOFs） are a new class of porous materials, which havepotential applications in a wide range of areas including catalysis, gas storage, separation, andsensors. Owing to their high surface area, porosity, and chemical tunability, the utilizations ofMOFs in heterogeneous catalysis or as catalyst support of noble metal nanoparticles haverecently attracted tremendous attention. In this thesis, MOFs were utilizied as the support toprepare highly dispersed Pd nanoparticles, and their catalytic performance were evaluated inhydrogenation reactions.The Pd-doped catalyst, Pd@MIL-101, was prepared by impregnating method. Thephysical and chemical properties, such as surface area, pore size, pore volume, strength ofacid sites, and the dispersion and diameter of Pd particles etc., were thoroughly characterizedby N₂adsorption, NH3-TPD, TGA, and HRTEM in this study. The catalytic performances ofthe Pd@MIL-101catalysts in the one-step synthesis of MIBK form acetone and H2in theliquid phase were investigated. It was shown that the MIL-101supported Pd catalysts areefficient bifunctional catalysts for the one-step synthesis of MIBK. Optimization of catalystcomposition and reaction temperature has led to the best results in this work. The highestMIBK yield for liquid-phase one-step synthesis of MIBK was achieved over0.11wt%Pd@MIL-101catalyst at150°C and an initial hydrogen pressure of0.75MPa （at roomtemperature）. This process produced MIBK with a selectivity of90.2%at60%acetoneconversion, which is much better than the best result reported to date even under relativelymild conditions. The strong acidity and high dispersion of the Pd@MIL-101catalyst couldaccount for the excellent reaction performance of the catalyst in the one-step synthesis ofMIBK.There have been a number of reports on the immobilization of noble metal nanoparticleson MOFs by employing various preparation methods, such as impregnation, colloidaldeposition, solid grinding, and chemical vapor deposition. In spite of these promisingapproaches, the development of a facile and efficient route to incorporate small noble metalnanoparticles with high catalytic activity in MOFs is of great importance and still remains challenging.Herein, we report the synthesis of a novel3D Tm-containing MOF （Tm-MOF） withcarbonyl groups pointing to the channels, which are not coordinated with any metal ions. Byusing the predesigned MOF as host, we have successfully incorporated small palladiumnanoparticles into the pores by a simple impregnation method. Moreover, the as-synthesizedPd/Tm-MOF composite exhibited a high catalytic activity in the hydrogenation of styrene. Tothe best of our knowledge, this work represents the first example of utilizing uncoordinatedcarbonyl groups to immobilize metal nanoparticles on MOFs as a highly active catalyst inheterogeneous catalysis.