Synthesis of a core-shell-shell structured acid-base bifunctional mesoporous silica nanoreactor (MS-SO3H@MS@MS-NH2) and its application in tandem catalysis

An efficient and facile method was designed to produce an acid-base bifunctional mesoporous silica nanoreactor (MS-SO3H@MS@MS-NH2) with acid sites on the inner core, unfunctionalized silica as the neutral zone shell and basic sites on the outer shell. Such acid core-neutral zone-base shell structure design resulted in excellent spatial separation of the hostile functionalities and was better than that of the core-shell structure. The spatial order of acid sites and basic sites in the mesoporous silica nanosphere offered a designated diffusion pathway that was favorable for reaction species, while the mesoporous structure endowed the material with the confinement effect. As a result, the core-shell-shell structured mesoporous silica nanosphere was an excellent bifunctional catalyst for one-pot cascade reaction sequences.