Templating metal-organic framework into fibrous nanohybrids for large-capacity and high-flux filtration interception

Abstract

Engineering metal-organic-frameworks (MOFs) into flexible hybrid membranes has been endeavored to entrap various molecules through a conventional filtration process. In most cases, both the rejection ratio and adsorption capacity may be limited by a low MOF loading amount, polymeric coating barrier, or large flow flux. It remains challenging to achieve the combination of large-capacity adsorption, high flux and large rejection ratio in an individual filtration setup. Herein through an in-situ templating synthesis, nanofibers of zeolitic imidazolate frame work-8 (ZIF-8) with the distinct diameters of ~20 nm and ~100 nm were produced by coating on aramid nanofibrils and silk microfibrils, respectively. With the super loading amount of ZIF-8 up to ~70 wt%, these fibrous nanohybrids enabled to produce spider-web-like membranes with both the high rejection ratio (>99%) and large flow flux (up to ~390 L m-2 h-1 bar-1 at thickness of ~120 μm). Their superior adsorption capacities for organic dyes also ensured the maintenance of high rejection ratios at high flow flux for large-volume filtration. Thus, the template of two types of nanofibrils may offer a facile method to design web-like MOF membranes with hierarchical microstructures and to intercept a large amount of specific molecules through a continuous “one-pass” filtration process for practical applications.