Rational construction of hybrid silica encapsulated ZIFs-derived carbons in mixed matrix membranes for enhanced carbon capture

Abstract

Polymer-filler interfacial compatibility is a critical issue in the fabrication of mixed matrix membranes (MMMs) for carbon capture because of the property discrepancies between the polymer phase and the filler phase, especially for carbon-based porous fillers in an organic polymer matrix. In this work, we constructed a type of carbon-based nanofiller with a functional shell. A layer of hybrid silica shell (hSi) was formed on zeolitic imidazolate frameworks-derived carbons (ZIC) via a facile sol-gel and grafting process, endowing it with rational porosity and functional sites. ZIC@hSi nanoparticles were then blended with a PEO-based membrane matrix to prepare ZIC@hSi/XLPEO membranes. The corresponding MMMs containing ZIC@hSi nanoparticles exhibit higher mechanical strength and CO₂/N₂ selectivity than MMMs containing bare ZIC nanoparticles because covalent linkages between the shell layer and the polymer matrix strengthen their interfacial compatibility. Moreover, the CO₂ permeability of ZIC@hSi/XLPEO membranes is 2.48 times higher than that of neat XLPEO membranes as the functional shell layer maintains gas accessibility to the porosity of the core layer, providing MMMs with fast gas transport channels for CO₂. Consequently, the ZIC@hSi/XLPEO membrane achieves a CO₂ permeability of 668 Barrer and a CO₂/N₂ selectivity of 58.7, surpassing the upper bound (2019). This strategy of constructing a functional shell layer on carbon-based microporous fillers has been proven to be an efficient approach to mitigate interfacial defects in MMMs.