Deep Eutectic Solvent Engineered Dendritic Fibrous Nano-Silica Catalyst for Sustainable Fixation of CO2 Into Value-Added Product at Atmospheric Condition

Abstract

Developing efficient carbon dioxide (CO₂) capture and conversion methods is vital for climate change mitigation. Cycloaddition of CO₂ with epoxides to form cyclic carbonates is a promising utilization method. In this study, a deep eutectic solvent-modified dendritic fibrous nano-silica (DES@DFNS) catalyst was synthesized by functionalizing DFNS with DES. This catalyst was used for the cycloaddition of CO₂ with styrene oxide to produce styrene carbonate. The material's morphology and properties were characterized using various analytical techniques, revealing a high surface area, good porosity, and significant concentrations of Lewis acidic and basic sites. Rietveld refinement analysis provided insights into its phase composition, crystallite size, microstrain, stress, and other microstructural properties. Despite a lower surface area, DES@DFNS demonstrated superior catalytic activity. The interaction between DES and DFNS showed that DES was physically adsorbed onto the DFNS surface, contributing to its enhanced performance. Factors such as smaller crystallite size, higher microstrain, increased dislocation density, and improved elastic properties provided more active sites and greater mechanical stability, boosting overall efficiency and durability. The DES@DFNS catalyst achieved 99% conversion of styrene oxide with 96% selectivity and 95% yield of styrene carbonate at 120 °C for 10 h under solvent-free, atmospheric conditions. The synergistic effect of Lewis acidic and basic sites on DES@DFNS supported catalytic activity under moderate conditions. Additionally, the catalyst demonstrated reusability, maintaining performance for up to six cycles without significant loss of activity, making it a promising candidate for sustainable CO₂ fixation and valorization processes.