Facile fabrication of nanoscale hierarchical porous zeolitic imidazolate frameworks for enhanced toluene adsorption capacity

Abstract: The development of a simple and facile synthesis route is a highly desirable but challenging process in the fabrication of nanoscale hierarchical porous zeolitic imidazolate frameworks (ZIFs). Herein we describe a facile method for rapidly synthesizing hierarchically porous ZIF-90 nanocrystals (particle sizes of ~ 300 nm) using hydroxyl double salts as intermediates at room temperature. The as-synthesized ZIF-90 contained hierarchical porous structures developed using a crystalline interior and a random stack of multiple nanoparticles. Both the morphology and particle size of ZIF-90 nanocrystals could be tuned by controlling the molar ratio of ICA/Zn²⁺. Note that the as-synthesized hierarchically porous ZIF-90 nanocrystals exhibited higher thermal stability compared with the conventional ZIF-90. Because of the introduction of hierarchical porous structures, the resultant hierarchically porous ZIF-90 nanocrystals showed enhanced toluene adsorption capacity than those of conventional metal organic frameworks and zeolites. Graphic abstract: [Figure not available: see fulltext.]