(92c) In-Situ Growth of 2D ZIF-L MOF on an Ultrafiltration Membrane: Understanding MOF Growth, Characterization, and Performance in the Removal of Emerging Pollutants

Zeolitic Imidazole Frameworks (ZIF) Metal Organic Frameworks (MOFs) are acclaimed materials due to their high specific surface area, porosity, and facile synthesis methods. The ZIF-8 MOF, a 3D material, has been widely studied in adsorption, catalysis, and gas separation. However, its 2D counterpart, ZIF-L, has not been comprehensively studied. The main objective of this work is to study the crystallization and in-situ growth mechanism of 2D ZIF-L MOFs on Polyethersulfone (PES) UF membranes with different reaction times extended to 48 hours. The physico-chemical properties of the ZIF-L MOFs at different time intervals (0-48 hours) were studied both in free solution and on in-situ PES-UF membranes using XRD, SEM, FTIR, BET, and Zeta Potential instruments, respectively. The ZIF-L functionalized PES-UF membranes underwent performance evaluation, including pure water permeability physical, and chemical stability of the ZIF-L MOFs with respect to growth time. The 24-hour MOF growth on PES-UF membrane showed micron-sized MOFs with layer defects, while the 48-hour counterpart had no micron-sized defects, leading to the formation of a robust ZIF-L MOF selective layer. The minimal leaching of the MOFs (less than 5%) in 12 hours also validated the robustness of the ZIF-L layer. The negative surface charge of the PES-UF membrane turned positive after ZIF-L functionalization, serving as an adsorptive membrane for negatively charged pollutants. the adsorptive capability of MOF-membranes was evaluated towards negatively charged Methyl Orange (MO) and Reactive Orange 16 (RO-16) dyes and the 48-hour ZIF-L functionalized membrane showed 42% and 45% removal, respectively, while the PES-UF (control sample) had only 9% rejection for both dyes. Furthermore, the 48-hour ZIF-L functionalized membranes were challenged with negatively charged sub-100 nm polystyrene nanoplastics, demonstrating more than 99% removal.