In-Situ MgO engineered dendritic fibrous nano silica as an efficient catalyst for fixation of CO2 at atmospheric pressure

The utilization of carbon dioxide (CO₂) for the synthesis of value-added chemicals is widely recognized as a sustainable strategy to mitigate global warming and promote environmental sustainability. In this study, we have designed an in-situ magnesium oxide substituted engineered dendritic fibrous nanosilica (MgO@DFNS) catalyst for the chemical fixation of CO₂ into cyclic carbonates under atmospheric pressure. A series of catalysts with varying MgO loadings (X wt.% MgO@DFNS) were synthesized via a simple, one-pot hydrothermal method. The structural and physicochemical properties of the synthesized materials were comprehensively characterized using advanced various analytical and spectroscopic techniques. In particular, their microstructural and elastic properties were examined through Rietveld refinement and theoretical simulations. To evaluate catalytic performance, MgO@DFNS catalysts were screened for the conversion of CO₂ and styrene oxide into styrene carbonate at 120 °C for 6 h under atmospheric pressure. Among the tested catalysts, the 10 wt% MgO@DFNS demonstrated the highest catalytic activity, achieving 96 % conversion of styrene oxide with 92 % selectivity toward styrene carbonate. Reaction parameters such as catalyst dosage, base amount, temperature, and reaction time were systematically optimized. Under these optimized conditions, the catalyst also exhibited broad substrate scope with good to excellent product yields across various epoxides. Notably, the superior catalytic performance is attributed to the inherent properties of the MgO@DFNS catalyst, including high thermal stability, large specific surface area, appropriate pore size distribution, unique wrinkled radial morphology, and a high density of active sites. Furthermore, the catalyst demonstrated excellent recyclability, maintaining its structural and physicochemical integrity over six consecutive reaction cycles. The earlier reported silica-based catalysts were well correlated with the present work in detail. A plausible reaction mechanism for the CO₂ fixation process was proposed supported by characterization and experimental results catalyzed by MgO@DFNS surface.