Improving Hydrothermal Stability and Catalytic Activity of Metal–Organic Frameworks by Graphite Oxide Incorporation

Abstract

This paper aims to improve the hydrothermal stability and catalytic activity of metal–organic frameworks (MOFs), which are believed to play an important role in the practical applications of MOFs in catalysis. Our strategy is to incorporate graphite oxide into a typical MOF, namely HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylic acid; HKUST = Hong Kong University of Science and Technology), and the properties of MOF are successfully tailored by use of this strategy. The obtained MOF/graphite oxide composites show enhanced porosity with high surface areas and some meso/macropores. For the composite containing 8.7 wt % of graphite oxide, the surface area reaches 1257 m2 g–1, which is obviously higher than pure HKUST-1 (841 m2 g–1). The pore structure of composites favors the access of reactant molecules to active sites and accelerates mass transfer in channels. Furthermore, the incorporation of graphite oxide creates a more hydrophobic environment surrounding metallic sites, which prevents the coordination bonds from attacking by water molecules and presents better affinity of active sites to organic reactants. Hence, the hydrothermal stability of MOF as well as the catalytic performance with regard to both activity and reaction rate are greatly improved. For the composite incorporating 8.7 wt % of graphite oxide, the conversion of styrene oxide in the ring-opening reaction can reach 74.1% after reaction for only 20 min, which is much higher than pure HKUST-1 (10.7%). More importantly, the catalytic activity can be well recovered without any loss even after six cycles. The excellent hydrothermal stability, catalytic activity, and reusability make our materials highly promising for use as heterogeneous catalysts in practical applications.