H3PW12O40 Encapsulation by Nanoporous Metal Organic Framework HKUST-1: Synthesis, Characterization, Activity and Stability

摘要

Hybrid composite material was obtained through encapsulation of H3PW12O40 (PW) into HKUST- (Cu-3 (BTC)(2), BTC = 1,3,5-benzenetricarboxylic acid), in molar composition of 5 Cu(NO3)(2) . 3H(2)O /2.8 BTC/ 0.3 PW/ 0.6 CTAB by adding solutions of PW and copper salts to mixture of BTC and surfactant. The catalyst was characterized by various techniques including powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), laser particle size analyzer, Brunauer Emmett-Teller (BET). The acidity of the catalyst was measured by a potentiometric titration with n-butylamine and PW/ HKUST-1 presented very strong acidic sites with Ei > 100 mV. This nano catalyst was successfully used for the synthesis of various beta-keto enol ethers at 45 degrees C with 51-98% yield after 5-75 min. The catalyst was easily recycled and reused at least four times without significant loss of its activity (94% yield after forth run). The presence of the PW in PW/ HKUST-1 and reused PW/ HKUST-1 structure, eliminating any doubt about collapse of the HKUST-1 after catalytic reaction and can be followed by FT-IR, XRD and SEM techniques. Bronsted and Lewis acidity of the PW/ HKUST-1 catalyst was distinguished by studying the FT-IR and determined by chemisorption of pyridine. The strength and dispersion of the protons on PW/ HKUST-1 was considerably high and active surface protons became more available for reactant.