Hierarchically porous MOF@COF structures with ultrafast gas diffusion rate for CH/CH separation. Journal of colloid and interface science For ethylene purification, CH-selective metal-organic frameworks (MOFs) show great potential to directly produce polymer-grade CH from CH/CH mixtures. Most CH-traping MOFs are ultra-microporous structures so as to strengthen multiple supramolecular interactions with CH. However, the narrowed pore channels of CH-traping MOFs cause large guest diffusion barriers, greatly hampering their practical applications. Herein, we present a feasible strategy by precisely constructing hierarchically porous MOF@COF core-shell structures to address this issue. Additional mesoporous diffusion channels were incorporated between MOF crystals through the construction of the COF shell, thereby enhancing the gas adsorption kinetics. Notably, designing a core-shell MOF@COF structure with an optimal coating amount of mesoporous COF shell will further improve the gas diffusion rate. Breakthrough experiments reveal that the tailored MOF@COF composites can effectively achieve CH/CH separation and maintain its separation performance over five continuous measurement cycles. This investigation opens up a new avenue to solve the diffusion/transfer issues and provides more opportunities and potentials for MOF@COF composites in practical separation applications. 10.1016/j.jcis.2024.04.227