Strongly co-ordinated MOF-PSF matrix for selective adsorption, separation and photodegradation of dyes

Abstract

Though adsorption and separation processes using metal–organic frameworks (MOFs) for water treatment are highly promising, the disposal of adsorbed or rejected contaminants still remains a major challenge. Herein, we report photocatalytic (PC) MOF-embedded polysulfone (PSf) membranes for separation and degradation of those contaminants, thus providing a solution for decontamination of water. Fe-based MOF, namely MIL-101(Fe), have been modified to incorporate amine functional groups (NH2-MIL-101(Fe)) to enhance the optical properties (possessing a bandgap of 1.7 eV) and to control the surface charges for the selective adsorption of contaminants. Such functional Fe-MOF, is embedded into polysulfone (PSf) membrane, to give photocatalytic MOF-membrane that is successfully applied for selective adsorption, separation and degradation of adsorbed contaminants. The MOF-integrated membranes were found to inherit the properties of MOFs, that confirmed the manifestation of hydrophilic properties in membranes. The intermolecular hydrogen bonding and π-π stacking between MOF and PSf facilitated strong coordination between them. Leaching studies demonstrate the intact MOFs in PSf matrix. Two model dyes, cationic rhodamine B (RhB) and anionic methyl orange (MO), were chosen for the study to demonstrate the selectivity of membranes towards these dyes. The obtained PC MOF-membrane showed an improved water flux together with good rejection and degradation efficiency. Antifouling capacity has been tremendously increased and above-par, reaching flux recovery ratio (FRR) values above 95%. This work offers insights into designing strongly coordinated functional PC MOF membranes with polychronic effects. Good water flux and antifouling capacity (are usually the bottlenecks in existing commercial membranes) achieved in these MOF membranes make them attractive candidates for pilot applications.