Mesoporous SBA-16/SO₃H from waste sugarcane bagasse ash for efficient Biginelli reactions

Sustainable, sulfonated mesoporous SBA-16 catalysts were synthesized from sugarcane bagasse ash (SCBA), an abundant agro-industrial waste from bio-energy production. SBA-16 modification with 3-mercaptopropyltrimethoxysilane (MPTMS) and subsequent oxidation to incorporate sulfonic acid groups, significantly enhanced the textural properties, achieving a surface area of 207 m²/g, while trace impurities from SCBA may enhance Lewis acidity. Such features improved catalytic efficiency and sustainability. A green assessment of catalyst synthesis from SCBA using the DOZN™ Green Chemistry Evaluator revealed that the SCBA-based methods are more sustainable than conventional TEOS-based methods. This study represents the first application of sulfonated SBA-16 for Biginelli reactions, yielding 99% for the reaction between benzaldehyde, methyl acetoacetate, and urea (at 105 °C, 7 h, 10 wt% catalyst, in ethanol). Catalysts demonstrated exceptional durability, with negligible loss of activity (~ 98%) over five consecutive cycles, highlighting its suitability for this application. SBA-16 catalysts exhibited broad substrate compatibility, particularly with electron-withdrawing groups across various aldehydes and β-diketones. The Biginelli reactions aligned with green chemistry principles, achieving favorable values for process mass intensity (PMI: 11.86-33.32 g/g), E-factor (10.86-32.32 g/g), solvent intensity (SI: 9.69-14.50 g/g), and water intensity (WI: 3.28-9.36 g/g). The Green Motion sustainability assessment tool score was 75/100. Sulfonated SBA-16 catalysts offer a sustainable alternative to commercial silica, with superior performance, reduced catalyst loading, and minimized environmental impact, underscoring its potential for use in industrial applications.