Controllable Synthesis, Diffusion Study and Catalysis of Hierarchical Zeolites

Hierarchical zeolites refer to zeolitic materials having bi-/multi-modal interconnective pores arranged in order of certain ranks, which improve the molecular diffusion within their frameworks, and hence the performance in their applications such as adsorption and heterogeneous catalysis. Hierarchical zeolites are commonly produced via the top-down post-synthetic treatments(such as dealumination and/or desilication) of pre-synthesized zeolites(i.e. the parent zeolites) and the bottom-up synthesis-by-design methods(such as soft/hard templating). This review presents the recent advances(mainly post 2000) in the strategies of making hierarchical zeolites, with the emphasis on the top-down approaches due to their relatively high practicality. Since hierarchical zeolites are proposed to improve intracrystalline diffusion, experimental studies of guest molecules diffusion in hierarchical zeolites are also reviewed. Additionally, catalytic applications of hierarchical zeolites, in comparison with the conventional microporous pristine zeolites, are also commented to highlight the advantages of hierarchical zeolites to improve catalysis.