Highly effective synthesis of dimethyl carbonate over CuNi alloy nanoparticles @Porous organic polymers composite

Abstract

Greenhouse effect raised by the carbon dioxide emissions has become a pivotal resolved issue at present. The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol is one of infusive green pathways. In this study, a novel CuNi alloy nanoparticles encapsulated in a thermal stable triphenylphosphine porous organic polymers (POP-PPh3), CuxNiy@POP-PPh3 catalysts, is synthesized and then explored in the direct DMC synthesis reactions. The CuxNiy@POP-PPh3 catalysts are fully characterized by a series of techniques, such as transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), and hydrogen temperature programmed reduction (H2-TPR). TEM images show the CuNi particles are around 7 nm, and XPS analyses demonstrate the alloy particles comprise of a metallic (CuNi)0 core and a thin Ni2O3 surface. The CuxNiy@POP-PPh3 catalysts, fixed into a honeycomb ceramic to give a monolithic catalyst, show an excellent catalytic performance (a 10.5% methanol conversion with an 80% DMC selectivity) during the direct DMC synthesis reactions in a fixed bed reactor. The high catalytic performance over CuxNiy@POP-PPh3 catalysts is mainly attributed to the pore structure of POP-PPh3, uniform distribution of alloy nanoparticles, and the unique performance of the monolithic catalyst (e.g., removing by-product of water in time).