Recent Advances in Catalytic Confinement Effect within Micro/Meso-Porous Crystalline Materials

Micro/meso-porous crystalline materials with a well-defined pore structure, such as zeolites, carbon nanotubes, and metal-organic frameworks, are of great significance in the development of catalytic systems for scientific and industrial demands. The confinement effect aroused by pore features of porous crystalline materials has triggered great interest in heterogeneous catalysis. Catalytic reactions in confined spaces exhibit unique behaviors compared to those observed on bulk materials. More interestingly, chemical reactivity can be modulated in different ways by the confinement effect, despite the fact that the mechanism on how the confinement effect changes the reaction remains unclear. In this review, a systematic discussion and fundamental understanding is provided concerning the concept of confinement effect, highlighting the impact of confinement effects on diffusion, adsorption/desorption, and catalytic reaction in typical micro/meso-porous crystalline materials, including zeolites, carbon nanotubes, and metal-organic frameworks. Relevant studies demonstrate that confinement effect affords not only shape selectivity against reactants/products, but also modulates surface electron distribution of active species confined within porous environments, thereby successively affecting the catalytic reactivity, selectivity, and stability. This review provides a useful guide for researchers attempting to design excellent porous crystalline catalysts based on the concept of confinement effect in heterogeneous catalysis.