Solvent-Free Synthesis of HKUST-1 with Abundant Defect Sites and Its Catalytic Performance in the Esterification Reaction of Oleic Acid

HKUST-1 has received increasing attention because of its potential applications in many fields, such as heterogeneous catalysis, sensors, gas storage, and separation. Herein, we report that HKUST-1 can be facilely prepared by heating a ground mixture of copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid in an autoclave at 80 °C for 10 h. The data from nitrogen sorption show that the obtained material, named HKUST-1-free, possesses a high BET specific surface area of 1671 m²/g and a pore volume of 0.8 cm³/g. The results from acid-base titration indicate that the number of defect sites in HKUST-1-free is more than that in HKUST-1-solvent prepared by the solvothermal method. As a heterogeneous catalyst, HKUST-1-free gave a high yield (91%) of methyl oleate in the esterification reaction of oleic acid with methanol at room temperature compared to HKUST-1-solvent (70%). Additionally, it is proven that HKUST-1-free is a heterogeneous catalyst and can be reused.