Metal-Organic Framework (MOF) functionalized membranes have garnered significant attention for precise gas and liquid separation applications. There is an increased attention to utilizing the MOF as the main selective layer among the functionalized membranes. The in-situ growth method is considered reliable as it eliminates MOF aggregation and uneven distribution issues that lead to defective membranes. In this study, a Zeolitic Imidazolate Framework (ZIF-L) MOF was in-situ synthesized using a solution-based room temperature (SBRT) method on a Polyethersulfone (PES) UF membrane by leveraging the -OH and -NH2 groups of the PDA. The MOF growth kinetics (from 30 min to 48 h) revealed that 48 h was the optimal time to achieve a 20 µm thick and compact ZIF-L MOF layer. The 24 h and 48 h ZIF-L functionalized membranes exhibited water permeabilities of 24 LMH/Bar and 12 LMH/Bar, respectively. The water permeability measured at different time scales provided valuable insights into the ZIF-L growth characteristics on the PDA-coated PES membrane. The confined growth of ZIF-L within the PDA layer required at least 10 h to increase the water permeability compared to PDA coated membrane. The permeability reached its maximum value at 24 h synthesis time, equivalent to the pristine PES UF membrane. After 24 hours, the water permeability of the ZIF-L functionalized membranes decreased as the defects and compactness of the ZIF-L layer improved. The ZIF-L functionalized membranes exhibited no MgSO4 salt selectivity. The Zeta Potential showed both 24 h and 48 h ZIF-L functionalized membranes were positively charged till pH 8. When challenged with negatively charged Methyl Orange (MO) and Reactive Orange 16 (RO-16) dyes, the rejection rates for the 48 h functionalized membrane improved to approximately 41% and 44%, respectively. This enhancement was significant as compared to the Blank-PES and PDA-coated membranes (~10%) due to both adsorption and size exclusion mechanisms.
