Morphology Effect of Metal-organic Framework HKUST-1 as a Catalyst on Benzene Oxidation

An attempt was made to study whether the morphology effect of metal-organic frameworks HKUST-1 could significantly influence the chemical reaction of benzene oxidation. Four representative cupric salts, CuSO4 center dot 5H(2)O, Cu(OAc)(2)center dot H2O, CuCl2 center dot 2H(2)O and Cu(NO3)(2)center dot 3H(2)O, were treated with 1,3,5-benzenetricarboxylic acid under ultrasound or with static method at room temperature to prepare metal-organic frameworks(12 types of HKUST-1 samples). And the as-prepared HKUST-1 materials were comprehensively investigated by X-ray diffraction, scanning electron microscopy and N-2 adsorption-desorption. The HKUST-1 samples with different morphologies and characterisitcs were employed as catalysts for benzene oxidation with H2O2 as oxidant at 60 degrees C in acetonitrile to achieve the aromatic oxygenates and test their yields. In all the HKUST-1 samples, the HKUST-1/SA, HKUST-1/SA0 and HKUST-1/UN had the higher catalytic activities with the yields of benzene oxygenates of 15.9%, 16.6% and 11.7%, respectively, which can be ascribed to the larger pore volume, the stronger benzene adsorption and the smaller fine crystal particles. Comparatively, the HKUST-1/SN0 and HKUST-1/SC0 with more intact crystal, larger surface area, lower pore volume and weaker benzene adsorption had the lower catalytic activities with the yields of benzene oxygenates not more than 4%. Therefore, our results confirmed that employing various cupric precursors to prepare the HKUST-1 samples with different morphologies and characteristics can be considered as a worth strategy to design many more powerful heterogeneous catalysts.