Preparation And Characterization Of Catalytic Materials Based On UiO-66

UiO-66 is a new subclass of metal-organic frameworks?MOFs?comprised of ordered networks which are formed by inorganic Zr₆O₄?OH?₄ cluster and terephthalate linkers.UiO-66 structure is assembled of tetrahedron cages and octahedron cages.UiO-66 has been emerging as very promising functional material for gas adsorption,separation and catalysis due to its tunable linker defects,large surface areas,high thermal and chemical stabilities.UiO-66 can be used as heterogeneous catalyst and prepared metal oxides owing to the unique advantages exhibited its tunable linker defects and as precursor.In this work,the application of UiO-66 as heterogeneous catalyst and precursor for preparing Zr-based oxides was investigated.The results are as follows:?1?UiO-66 as an efficient and reusable catalyst for transesterification of triglyceride with methanolA series of zirconium-containing UiO-66 samples were synthesized by varying the synthesis temperatures and BDC/Zr?terephthalic acid/ZrCl₄?ratios in the synthesis system.The synthesized UiO-66 samples were characterized by XRD,N₂ adsorption-desorption,TGA and NH₃-TPD.Their catalytic performances were investigated in transesterification of tributyrin and soybean oil with methanol.The results showed that UiO-66 samples with different amount of defects could be successfully prepared by varying the synthesis temperatures and/or the BDC/Zr ratios used in the synthesis system.The catalytic activities of the UiO-66 materials greatly depended on their linker defects and enhanced with the increase of the defect amount.The UiO-66 was an efficient catalyst for transesterification of tributyrin and soybean oil with methanol.The UiO-66 catalyst was relatively stable and could be reused.?2?Synthesis of mesporous and tetragonal zirconia with inherited morphology from UiO-66Mesoporous and tetragonal zirconia?t-ZrO₂?was prepared from metal-organic framework?UiO-66?,acting as both morphological template and zirconium source.After thermal decomposition at 500°C,t-ZrO₂ inherited octahedral morphology from the pristine precursor,and possessed small nanoparticles with an average size of 3.1 nm.The derived t-ZrO₂ had a large surface area of 174 m²/g and the pore diameter of 5-8 nm.The formation mechanism of t-ZrO₂ was also discussed.This simple and potentially universal strategy can be used to fabricate porous metal oxides with desired shape for many applications.?3?“One-pot”preparation and characterization of mesporous SO₄^2-/ZrO₂SO₄^2-/UiO-66 sample was first synthesized by adding?NH₄?₂SO₄ into the synthesis system of UiO-66.Subsequently,the as-synthesized SO₄^2-/UiO-66materials were employed as precursors and morphological templates for preparing mesporous SO₄^2-/ZrO₂.SO₄^2-/ZrO₂ materials were prepared by calcining SO₄^2-/UiO-66 at a certain temperature in air.The prepared mesporous SO₄^2-/ZrO₂ were characterized by SEM,XRD,N₂ adsorption,IR pyridine and glycerol esterification with acetic acid.The results show the derived SO₄^2-/ZrO₂was assembled from large nanoscaled plates and well inherited the pristine flower-like morphology of precursor.At calcination temperature of 500^oC,the obtained SO₄^2-/ZrO₂ was tetragonal,but tetragonal phase of SO₄^2-/ZrO₂transformed into monoclinic phase with increasing calcination temperature.The acid amounts,BET surface areas and pore volumes of the SO₄^2-/ZrO₂ materials also decreased with increasing calcination temperature.SO₄^2-/ZrO₂ catalyst exhibited much higher catalytic activity for glycerol esterification with acetic acid as compared with ZrO₂.The catalytic performance of SO₄^2-/ZrO₂ decreased with calcination temperature increased.