Hydrophilic Three-Dimensional Covalent Organic Polymer Membranes for Aqueous Molecular Separation

Fine molecular separation processes are crucial for modern industry. In this work, through a room-temperature oligomer interface ripening method, three-dimensional covalent organic polymer tetra(4-aminophenyl) methane–dihydroxybenzaldehyde (TAPM–DHTA) membranes were successfully prepared for aqueous phase molecular separation. Fourier-transform infrared and X-ray photoelectron spectroscopy characterizations confirmed the formation of imine bonds in the TAPM–DHTA membranes. Scanning electron microscopy images revealed that the membranes exhibited a uniform and dense structure, with an adjustable thickness ranging from 130.9 to 236.1 nm as the reaction time was extended from 12 to 36 h. The TAPM–DHTA membranes exhibited an impressive rejection efficiency exceeding 90% for the four dyes: Alcian blue, Evans blue, Coomassie blue, and Congo red. Meanwhile, the TAPM–DHTA-24 h membrane showed high rejection for some pharmaceutical ingredients, such as vitamin B12, bacteriocin, and rifampicin. The membrane demonstrated excellent long-term stability during molecular separation. The findings suggest that the TAPM–DHTA membranes effectively meet the stringent molecular sieving and durability criteria essential for practical separation applications.