Cationic dyes persist in water not because they are hard to recognize, but because most adsorbents cannot engineer the right electrostatic microenvironments without sacrificing crystallinity, porosity, or recyclability. Here, we encode phenolate-rich anionic pockets into the pore walls of two π-conjugated 2D covalent organic frameworks, TU-331 and TU-332, constructed by symmetry-matched Schiff-base reticulation of 2,4-dihydroxybenzene-1,3,5-tricarbaldehyde with C3-symmetric triamine linkers. The resulting honeycomb lattices exhibit permanent microporosity while presenting oxygen-rich, negatively polarized interfaces that preferentially bind aromatic cations. TU-331 delivers rapid and high-capacity uptake of basic green 1 and methylene blue (qmax = 302.7 and 280.0 mg g–1), far exceeding adsorption of sulfonated azo anions. Zeta-potential and pH studies reveal electrostatic amplification of binding under basic conditions, enabling efficient regeneration with ∼99.5% capacity retention after five cycles. Importantly, TU-331 decolorizes authentic multicomponent textile dyeing effluents from a commercial facility, demonstrating function under viscosity- and additive-rich industrial matrices. Density functional theory (DFT) and symmetry-adapted perturbation theory (SAPT) analyses quantify the selectivity origin: strongly favorable binding for cationic dyes (∼−140 kcal mol–1), dominated by Coulombic attraction and dispersion-driven π stacking, versus unfavorable association for anionic dyes. These results establish reticular microenvironment design as a blueprint for charge-selective dye capture in real wastewater.
Nozaki et al. (Wed,) studied this question.