Membrane-based purification and recovery of phosphate and antibiotics by two-dimensional zeolitic nanoflakes.

The pervasive presence of persistent contaminants in water resources, including phosphate and antibiotics, has attracted significant attention due to their potential adverse effects on ecosystems and human health. Adsorption membranes packed with metal-organic frameworks (MOFs) have been proposed as a potential solution to this challenge due to their high surface area to volume ratio, and the tailored functionality they can provide for selective purification. However, devising a straightforward method to enhance the stability of MOF membranes on polymer supports and manipulate their surface morphology remains challenging. In this study, we present a facile solution immersion technique to fabricate a ZIF-L adsorption membrane on commercial supports by leveraging the self-polymerization characteristics of dopamine. The simple coating methodology provides a polydopamine-lined interface that regulates the ZIF-L heteroepitaxial growth, along with tailored nanoflake morphology. Compared with crystals prepared in bulk solution, the sorbents grown on the membrane exhibit a higher saturation capacity of 248 mg g of phosphate (∼80 mg phosphorus per g sorbent) and 196 mg g for tetracycline in static adsorption experiments at 30 °C. Additionally, the membranes are capable of selectively removing 99.5% of the phosphate in simulant solutions comprising competitive background ions in various concentrations, and efficiently removing tetracycline. The result from the static adsorption experiments directly translates to a flow-through process, showcasing the utility of a composite membrane with a 3 μm thick active layer in practical adsorption applications. The facile solution immersion fabrication protocol introduced in this work may offer a more efficient paradigm to harness the potential of MOF composite membranes in selective adsorption and resource recovery applications.