Gradient Hierarchically Porous Structure for Rapid Capillary-AssistedCatalysis

Synthesis of hierarchically porous structures withuniform spatial gradient and structure reinforcement effect stillremains a great challenge. Herein, we report the synthesis ofzeolite@mesoporous silica core-shell nanospheres (ZeoA@MesoS) with a gradient porous structure through a micellardynamic assembly strategy. In this case, wefind that the size ofcomposite micelles can be dynamically changed with the increase ofswelling agents, whichin situact as the building blocks for themodular assembly of gradient mesostructures. The ZeoA@MesoSnanospheres are highly dispersed in solvents with uniformmicropores in the inner core and a gradient tubular mesoporeshell. As a nanoreactor, such hierarchically gradient porousstructures enable the capillary-directed fast mass transfer from thesolutions to inner active sites. As a result, the ZeoA@MesoScatalysts deliver a fabulous catalytic yield of similar to 75% on the esterification of long-chain carboxylic palmitic acids and high stability eventoward water interference, which can be well trapped by the ZeoA core, pushing forward the chemical equilibrium. Moreover, a veryremarkable catalytic conversion on the C-H arylation reaction of largeN-methylindole is achieved (similar to 98%) by a Pd-immobilizedZeoA@MesoS catalyst. The water tolerance feature gives a notable enhancement of 26% in catalytic yield compared to the Pd-dendritic mesoporous silica without the zeolite core

Automated summary

In this study, zeolite@mesoporous silica core-shell nanospheres with a gradient porous structure were successfully synthesized using a micellar dynamic assembly strategy. These nanospheres are highly dispersed in solvents, with uniform micropores in the inner core and a gradient tubular mesopore shell. As a result, they exhibit excellent catalytic performance and high stability even in the presence of water interference.