Designing\nPhenolphthalein-Based Adsorptive Membranes\nfor the High-Affinity, High-Capacity Capture of Contaminants from\nWater

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