Synthesis of Robust MOF-Derived Cu/SiO₂ Catalyst with Low Copper Loading via Sol–Gel Method for the Dimethyl Oxalate Hydrogenation Reaction

Abstract

The insufficient catalytic stability of Cu-based catalysts is still its bottleneck in industrial application, and it is widely studied how to synthesize highly stable Cu-based catalysts. Herein, we have developed a MOF-derived preparation of robust Cu/SiO2 catalyst for the efficient hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The sol–gel method was used to in situ load the HKUST-1 into SiO2 support with only a copper loading of 7.83%. The advantages of MOF-derived Cu/SiO2 catalyst are that copper species could escape from severe coating by silica matrix and expose more active sites with small particles sizes (4.2 nm). Furthermore, it is inclined to generate more stable Cu2O reduced from Cu–O–Si units by using MOF as precursor. As a result, more than 95.0% selectivity of EG with a long lifetime of 220 h was achieved over the Cu/SiO2-MOF catalyst. On the contrary, when using the copper nitrate as the copper precursor, the prepared Cu/SiO2-CN catalyst with similar copper loading exhibited much lower catalytic activity because that copper species were encapsulated into SiO2 network and difficult to be available for reactants. Therefore, using MOF as copper precursor solves the problem of high-dispersed copper species but inactive by coating with SiO2 matrix.