Abstract
Herein, the incorporation sulfamic acid (SA) into mesoporous silica (MCM-41) introduced an effective approach in numerous multicomponent reactions. SA/MCM-41 composites with different weight content of SA were successfully synthesized through easy impregnation method. The as-synthesized composites were characterized by different techniques like SEM, EDX, TEM, XRD, BET and FT-IR spectroscopy. The acidic characters of the composites have been studied using FTIR of chemisorbed pyridine and non-aqueous potentiometric titration. TEM and XRD measurements approve that MCM-41 shows an ordered mesoporous structure with hexagonal and honeycomb lattice and its mesoporous structure did not change even after modification with SA. MCM-41 shows high surface area (1287 m2/g), which reduced after addition of sulfamic acid until reached to 611 m2/g at 90 wt% SA-MCM-41. The acidic strength of the prepared composites progressively improved by raising SA contents up to 75 wt% SA/MCM-41. The as-synthesized composites were tested for multicomponent reactions such as preparation of 3,4-dihydro-pirimidin-2(1H)-ones (DHPs), 7-hydroxy-4-methylcoumarin and 14-Phenyl-14H-dibenzo [a, j] xanthene. SA/MCM-41 catalysts displayed excellent performance in 14-phenyl-14H-dibenzo [a, j] xanthene (95.8%), 3, 4-dihydropyrimidinones (94.4%) and 7-hydroxy-4-methylcoumarin (96.7%). The prepared catalysts displayed excellent reusability without significant loss in catalytic performance from the fresh run.
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•A highly active and stable MCM-41 supported with sulfamic acid catalysts have been successfully synthesized.•All loaded catalysts exhibited distinct catalytic activity in synthesis of xanthene, dihydropyrimidinone and coumarin.•The catalysts showed an excellent yield % up to 95% in all reactions and also show excellent recycling efficiency.