An Environmentally Benign Solid Acid Nanocatalyst for the Green Synthesis of Carboxylic Acid Ester

Green and sustainable chemistry have gained substantial attention worldwide, and the efforts have been greatly appreciated for the substitution of Brønsted acid catalysts from homogeneous to heterogeneous phases. In this perspective, a sulfonic acid-functionalized silica nanospheres (SAFSNS) catalyst was prepared by organosilylation-sulfonation on the surface of well-ordered silica nanospheres as a heterogeneous nanocatalyst. The physicochemical properties of nanocatalyst were well characterized by powder XRD, IR, TGA, DSC, NH₃-TPD, N₂ sorption, EDAX, and SEM techniques. The attainment of the anchoring of SO₃H functionalization involving the Brønsted acidities was found up to 0.35 mmol H⁺/g. The synthesized SAFSNS nanocatalyst ascertain the replacement of the highly toxic liquid phase acids to a stable, solid acid catalyst for the green esterification of carboxylic acids under solvent-free reaction conditions, showed reasonable to excellent esters yield (63–94 %) in 3.5 hours at 100 °C with five times reusability without substantial diminution in catalytic proficiency.