The anisotropic surface functionalization of microporous zeolites with mesoporous materials into hierarchically porous heterostructures with distinctive physical and chemical properties is expected to significantly extend their applicability to catalysis. However, the precise control of the surface chemistry of zeolite crystals through site-specific interconnection with mesoporous materials remains a grand challenge. Here, we report a regioselective surface assembly strategy for the region-specific growth of mesoporous polymer/carbon on zeolite nanocrystals. The approach enables controllable regioselective surface deposition of mesoporous polydopamine on the edges, curved surfaces, or/and flat surfaces of the silicalite-1 nanocrystals into exotic hierarchical nanostructures with diverse surface geometries. Upon carbonization, their derived heterostructures with anisotropic surface wettability show amphiphilic properties. As a proof of concept, Pt nanoparticle-encapsulated silicalite-1/mesoporous carbon nanocomposites are tested to be interface-active for forming Pickering emulsions. Significantly, the catalysts show superior catalytic performance in shape-selective hydrogenation of various nitroarenes in a series of biphasic tandem catalytic reactions, giving ∼100% yield of corresponding amine products. The results pave a path toward rational construction of high levels of surface structural complexity in hierarchically porous heterostructures for specific physical and chemical characteristics in diverse applications.
Stable aluminosilicate zeolites with extra-large pores open through rings of more than 12 tetrahedra are in demand to process molecules larger than those currently manageable. However, until very recently, they proved elusive. Here we report a new strategy based on an interchain expansion design concept that yields thermally and hydrothermally stable silicates by expansion of a one dimensional (1D) silicate chain with an intercalated silylating agent that separates and connects the chains. As a result, new types of zeolites zeolites with extra-large pores delimited by 20, 16, and 16 Si tetrahedra along the three crystallographic directions, respectively, are obtained. The as-made inter-chain expanded zeolite contains dangling Si-CH3 groups that by calcination connect to each other resulting in a true, fully connected 3D zeolite framework with a very low density, just slightly above that of water. Additionally, it features triple four ring units never seen before in any type of zeolite. Ti can be introduced in this zeolite to obtain a catalyst active in the liquid-phase oxidation of bulky alkenes that shows promise in the industrially relevant clean production of propylene oxide using cumene hydroperoxide as an oxidant.
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