Designing Phenolphthalein-Based Adsorptive Membranes for the High-Affinity, High-Capacity Capture of Contaminants from Water

The selective removal of solutes is crucial for ensuring a sustainable water supply, recovering resources, and cost-effective biomanufacturing. Adsorptive membranes are promising in this regard due to their rapid mass transfer and low energy demands. However, state-of-the-art adsorptive membranes offer limited pore sizes and surface chemistries. This study reports the development of adsorptive membranes from reactive phenolphthalein-based (PPH-based) polymers. These polymers, which are molecularly engineered to possess a high density of reactive pendant groups, are transformed into porous membranes through a surface-segregation vapor-induced phase separation (SVIPS) method. Examining the thermodynamic characteristics of the polymer–solvent–nonsolvent system informs the SVIPS manufacturing process and facilitates the formation of diverse membrane morphologies with hydraulic permeabilities ranging from 3400 to 13,500 L m – 2 h –1 bar –1 . Copper ion binding experiments demonstrate a saturation capacity of 0.9 mmol Cu 2+ g –1, indicating high accessibility of the pendant groups for postsynthetic modification. Functionalization with alkyne groups enables one-step click reactions, such as the thiol–yne and Cu(I)-catalyzed azide–alkyne cycloaddition, expanding the membrane functionality. The incorporation of cucurbit[7]uril-azide macrocycles demonstrates the affinity-mediated capture of methyl viologen from solution. The combination of PPH-based polymers and the SVIPS method provides a versatile adsorptive membrane platform with a dense presentation of reactive sites, facilitating customization through diverse and high-yielding reactions.