Zwitterionic Imidazole-Urea Derivative Framework Bridged Mesoporous Hybrid Silica: A Highly Efficient Heterogeneous Nanocatalyst for Carbon Dioxide Conversion

The use of supported zwitterionic nanoparticles is an interesting and important strategy for the development of new CO₂ conversion catalysts with enhanced activity and selectivity. Several zwitterionic imidazole-urea derivative frameworks bridged mesoporous hybrid silica materials were prepared and characterized by using FTIR spectroscopy, solid-state NMR spectroscopy, X-ray photoelectron spectroscopy, XRD, TEM, and thermogravimetric analysis. The new Im-Si-X-ϕ materials possess a high surface area, hydrogen-bond donor ability, and nucleophilicity. The material that contains iodine and is protonated by an inorganic acid shows an excellent catalytic activity for CO₂ conversion into cyclic carbonates with good recyclability. Reaction parameters for the cycloaddition of CO₂ with propylene oxide to propylene carbonate were optimized. The one-component material is an efficient heterogeneous catalyst for CO₂ cycloaddition reactions and is a greener alternative to conventional supported transition-metal catalysts. Its catalytic features were also compared to those of the unsupported free ionic compound and other supported catalysts reported previously.