Macrocycle-assembled membranes for high-salinity organic wastewater treatment

Membrane processes offer a promising pathway for selectively separating organics and salts to enable water reuse and resource recovery. While polymeric membranes incorporating macrocyclic molecules that feature amphiphilic nature and tunable cavities are well suited for this purpose, traditional macrocycles with limited reactive sites and uncontrolled diffusion are challenging to be assembled into highly interconnected membranes. Here, we introduce tetra-aldehyde appended calixarene (TACA), a macrocyclic monomer featuring three-dimensional cavity and moderate reactivity, for creating loose-structured nanofilms via unidirectional diffusion assisted interfacial polymerization (UDIP). Precise positioning of the lipophilic TACA at the organic phase boundary allows it to polymerize with aqueous-phase diamines on the hydrogel surface, facilitating an undisturbed environment for controlled polymerization. The resultant thin macrocycle-assembled membranes featuring intrinsic water-facilitated through-cavity exhibited high water permeability of 63.8 L m-2 h-1 bar-1, and exceptional dye/salt selectivity and structural robustness, as evidenced by efficient diafiltration of binary dye/salt mixtures and superior operational stability. This work highlights the potential of macrocycle-assembled membranes for high-salinity organic wastewater treatment. Macrocyclic polymer membranes are well suited for wastewater treatment, though it is challenging to fabricate porous networks using macrocycles. Here the authors report a membrane containing tetraaldehyde appended calixarene using a unidirectional diffusion assisted interfacial polymerization method for a wastewater treatment membrane.