Novel DMAP@Mesoporous Silica Hybrid Heterogeneous Catalysts for the Knoevenagel Condensation: Greener Synthesis through Eco-friendly Solvents

Abstract

This article reports a sustainable synthesis of a novel organic-inorganic hybrid catalysts, featuring 4-(dimethylamino)pyridine (DMAP) immobilized onto mesoporous MCM-41 silica and amorphous Aerosil silica supports. Using (±)-2-methyltetrahydrofuran (MeTHF), a bio-based solvent, the covalent binding of DMAP to silica surfaces was achieved, reducing reliance on traditional petroleum-based solvents like toluene. The DMAP-functionalized hybrid catalysts, characterized through XRPD, TGA/DTA, FE-SEM, and FT-IR, demonstrated effective catalytic performance in the Knoevenagel condensation, a reaction relevant in producing fine chemicals and pharmaceuticals. The mesoporous MCM-41-supported catalyst exhibited superior activity due to its high surface area and ordered porous structure, with 97 % yield and 99 % selectivity. Stability and reusability were validated through leaching and recycling tests, confirming minimal DMAP leaching and robust catalytic performance over consecutive cycles. This green synthetic pathway underscores the potential of hybrid catalysts in advancing sustainable chemistry, promoting reduced energy consumption, and supporting a circular economy through recyclable, highly active catalysts in eco-friendly solvents. These findings demonstrate that MCM-41-supported DMAP hybrids are viable candidates for eco-friendly applications.