NH2-SiO2-C3H7 with abundant surface groups exposure as the efficient catalyst for the Aldol condensation reaction

• High ratio (86.5%) of the silicon species were exposed on the surface of. • SiO 2 -based materials. • High amount of organic groups (about 65 mol%) were successfully introduced. • Polar amino and silanol and weakly polar propyl supplied important synergistic effect. • Reaction time was obviously shortened to 25 min for the Aldol condensation reaction. The species and amount of the surface groups are closely related with the catalytic performance for a heterogeneous catalyst. High content of alkylamino (50 mol%) and n -propyl (15 mol%) were simultaneously introduced onto the surface of SiO 2 nanospheres with a one step reverse-phase microemulsion method. Accompanying the formation of plenty of surface nano-bulges, a high ratio (86.5%) of the silicon species were exposed on the surface of this novel material. Abundant of surface groups including Si-NH 2 (5.5 mmol g -1 ), Si-C 3 H 7 (1.7 mmol g -1 ), and Si-OH (6.1 mmol g -1 ) coexisted on the surface enabled this novel material to be a very efficient catalyst for the Aldol condensation reaction between benzaldehyde and n -heptanal. Higher content of alkylamino supplied more catalytic sites. Proper ratio of silanol-to-alkylamino (a little higher than 1) facilitated the adsorption of the substrate molecules and strengthened the cooperation between alkylamino and silanol. Surface hydrophobic modification with n -propyl further facilitated the adsorption of the substrate molecules at the presence of the byproduct of water. Conversion of 99% was successfully obtained at a lower temperature (90 o C) and in a very short time of 25 min with the present material being used as the catalyst. In some other Aldol condensation reactions, the present catalyst NH 2 -SiO 2 -C 3 H 7 also showed excellent catalytic performance.