Protein–polyphenol nanoassemblies modulated construction of zeolitic imidazole framework-67 based nanofiltration membrane for effective separation of dye/salt mixtures

Abstract

Metal–organic frameworks (MOFs) show great potential in various separation applications. However, fast nucleation rate and crystallization of MOFs, produce non-uniform and uncontrollable sized crystals, which are not suitable for the formation of MOF-based membranes. Herein, we propose the concept of utilizing protein polyphenol nanoassemblies (PPNs) as the building blocks for the confined growth of MOFs to fabricate zeolitic imidazolate frameworks (ZIF-67)-based membranes. We first demonstrated that colloidal PPNs as modulators in solution enables the formation of ZIF-67 MOFs with uniform and controllable crystal sizes. Subsequently, we utilized the metal salt coordinated PPNs (Co2+@PPN) as the precursor layer matrix deposited on porous polymeric support to fabricate ZIF-67 membranes via in-situ growth strategy at room temperature. The resultant membrane features a robust heterogeneous and well-integrated ZIF-67-reinforced PPN (ZIF-67@PPN) microporous networks. Benefiting from the rigid and multidimensional micropores of ZIF-67, the optimized ZIF-67@PPN1 composite membrane with improved water stability exhibited good water permeance (45.68 L m−2 h−1 bar−1), excellent dye desalination performance (Na2SO4/Congo red selectivity of 1271.47), and good antibiotic desalination performance (NaCl/Erythromycin selectivity of 21.46). The findings in this work provide important engineering concepts for the development of MOF-based membranes using sustainable nature-derived building blocks for emergent environment-relevant desalination applications in the chemical process industry.