Cycloaddition of CO ₂ and Epoxide at Ambient Conditions Catalyzed by PW ₁₂ @HKUST-1 Composite and Optimization Study Using RSM

Abstract

The search for a sustainable and effective catalyst for CO2 fixing using epoxides is part of a global quest for economical carbon capture and utilization solutions. The coupling of metal–organic frameworks (MOFs) with other functional nanomaterials such as polyoxometalates (POMs) has proven to be effective in increasing the heterogeneity and stability of pristine MOF materials. We demonstrated the application of MOF/POM-supported composites (POM@MOF) as catalysts for the fixation of CO2 and epichlorohydrin epoxide (ECH) to chloropropene carbonate. The catalyst was synthesized by impregnating HKUST-1 with (TBA)3PW12O40, a Keggin-type polyoxometalate. The obtained composite, PW12@HKUST-1, was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and N2 adsorption–desorption isotherms. The POM’s presence was confirmed by various analyses. Optimization of the reaction variables was conducted using the response surface methodology model. The optimum condition for the CCD-RSM studies was catalyst amount: 12.50 mg, cocatalyst amount: 0.055 mmol, temperature: 100 °C, and time: mechanism of CO2 conversion 15 h, attaining 89.70% conversion and 97% selectivity. The catalyst shows a remarkable increase in stability and reusability by recycling six times in a row without any significant decrease in catalytic activity.