One-pot synthesis of bimetal MOFs as highly efficient catalysts for selective oxidation of styrene
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Ó Indian Academy of Sciences Sadhana (0123456789().,-volV)FT3](0123456 789().,-volV)
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One-pot synthesis of bimetal MOFs as highly efficient catalysts for selective oxidation of styrene KAI HUANG*
, SIBING YU, XIAOXIN LI
and ZHENYU CAI
School of Chemistry and Chemical Engineering, Southeast University, Jiangning District, Nanjing 211189, China E-mail: [email protected] Kai Huang and Sibing Yu have contributed equally to this work. MS received 4 June 2020; revised 21 July 2020; accepted 10 August 2020
Abstract. A series of novel bimetallic organic framework materials (Cux-Coy-MOF) have been successfully prepared by a simple one-pot synthetic method, and their characters were evaluated via means of various techniques. The tested data showed a series of Cux-Coy-MOFs displayed good crystallinity and the doping of Co in original Cu-based framework would not change the morphology of the MOF catalysts. The catalytic activity of prepared materials was tested in the catalytic oxidation of styrene in the presence of TBHP. The effects of reaction time, reaction temperature and other reaction conditions on catalytic performance were systematically studied. The results revealed that the introduction of Co can improve the selectivity to form epoxides and reduce the yield of benzaldehyde without affecting the conversion rate of catalytic oxidation reaction of styrene. Excitingly, the Cu0.25-Co0.75-MOF showed better catalytic performance than Cu-MOF and Co-MOF under the optimal reaction conditions, the conversion rate of styrene reached 97.81%, and styrene oxide selectivity reached 83.04%, which indicated a significant synergistic effect of the Cu/Co bimetallic MOF. Furthermore, the Cu0.25-Co0.75-MOF catalyst exhibited good reusability that could be reused at least four times without significant inactivation. Keywords. Bimetallic MOF; styrene; oxidation reaction; synergistic effect.
1. Introduction The catalytic oxidation of styrene is an important reaction that has been paid close attention to by many researchers because styrene oxide as an organic intermediate was widely used in the synthesis of cosmetics, perfume and medicine.1,2 Numerous researchers over the past few decades have been working on catalysts that catalyze the oxidation of styrene. At present, homogeneous catalysts including transition metalSchiff base coordination compounds and heteropoly acids have been widely used in olefin catalytic oxidation systems.3–5 Although homogeneous catalysts have a high activity in catalytic oxidation of styrene, they are difficult to separate from the reaction system and cannot be effectively recycled.6 In contrast, the
heterogeneous catalysts formed by fixing homogeneous catalysts on various carriers including zeolites, organic polymers, Al2O3 and so on, which perfectly avoid the defects of homogeneous catalysts. Whereupon, many multiphase catalysts for the oxidation of olefin have been reported based on this advantage.7–12 Although homogeneous catalysts can be used to catalyze reactions by immobilizing solid
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