Preparation of thin-film composite membranes with ultrahigh MOFs loading through polymer-template MOFs induction secondary interfacial polymerization

Thin-film composite metal–organic frameworks (MOFs) membranes (TFCMMs) have huge potential to achieve good selectivity and high permeance in gas separation due to the ultrathin thickness of separation layer and the excellent properties of MOFs. In this work, we reported a TFCMMs with ultrahigh MOF loading and dense membrane structure through polymer-template MOFs induction secondary interfacial polymerization. The polymer-template ZIF-8 (BZIF-8) was prepared by branched polyethylenimine in-situ modified, which was post-doped in nascent polyamide (PA) layer in order to avoid defects of interfacial polymerization through in-situ doping. Under the effect of gravity, BZIF-8 could be embedded into the uncured nascent PA layer locally, resulting in the formation of dense TFCMMs with ultrahigh MOF loading up to 73.73 wt%. And BZIF-8 had rich grafted polymer fragment, which could improve interface compatibility and enhance structure-crosslinking of membranes by secondary interfacial polymerization between amino groups on the BZIF-8 and residual acyl-chloride groups on the nascent PA layer, realizing the regulation of membranes structure. The prepared membrane showed mixed N2 permeance of 5160 GPU with N2/CH4 selectivity of 7.38 and mixed CO2 permeance of 14588.23 GPU with CO2/CH4 selectivity of 23.1, which had high potential for CH4 purification.