Confinement of Ultrasmall Pd Clusters Within Nanosized ZIF-8-Derived Cu-N-C Materials for Efficient and Stable Synthesis of Glycerol Carbonate from Glycerol

Abstract

Copper-Nitrogen-Carbon (Cu-N-C) materials, derived from zeolite imidazolium frameworks, serve as promising carriers for catalyzing glycerol carbonylation reactions due to their modifiable pore size structure, enhanced catalytic selectivity, and stability. However, conventional palladium loading often results in the susceptibility of Cu-Pd co-catalysis loss, impeding practical application. In this investigation, we employed an in-situ confinement technique to embed polyvinylpyrrolidone (PVP)-modified palladium nanoparticles within the Cu-ZIF-8 metal framework, followed by direct calcination under a nitrogen atmosphere. This method yielded uniform-sized and shaped copper-palladium alloy catalysts, denoted as Pd@Cu-NC. Comparative analysis with catalysts prepared via impregnation followed by calcination revealed significantly enhanced stability of the resulting Pd@Cu-NC catalysts, with improved selectivity and stability of the active components. Notably, catalyst stability was markedly improved, and active component loss was mitigated. Under optimized conditions, a remarkable yield of 90.14% and selectivity of 99.91% were achieved, while retaining 77.43% activity after five cycles. Furthermore, density functional theory (DFT) calculations were employed to simulate the kinetics of carbon monoxide adsorption and glycerol dimethyl acetal (DMA) solution on various substrates. The presence of copper oxide notably reduced the adsorption energy of substrates to carbon monoxide and reaction solutions, thereby lowering the reaction activation energy and enhancing the reaction rate. This computational analysis provides further evidence of the beneficial role of copper oxide in facilitating the carbonylation reaction.

Graphical Abstract