Phenolate-Rich Anionic Covalent Organic Frameworks with Engineered Reticular Microenvironments Enable Selective Dye...

Area of Science:

• Materials Science
• Environmental Chemistry
• Supramolecular Chemistry

Background:

• Cationic dyes are persistent water pollutants.
• Existing adsorbents struggle to selectively remove them due to challenges in creating suitable binding environments without compromising material properties.
• The need for effective and recyclable adsorbents for dye removal is critical.

Purpose of the Study:

• To design and synthesize novel 2D covalent organic frameworks (COFs) with engineered anionic pockets for selective cationic dye adsorption.
• To investigate the adsorption capacity, selectivity, and recyclability of these COFs for textile dye effluents.
• To elucidate the binding mechanism and selectivity origin using computational methods.

Main Methods:

• Synthesis of π-conjugated 2D COFs (TU-331 and TU-332) via Schiff-base reticulation.
• Characterization of porosity, crystallinity, and surface properties.
• Adsorption experiments with cationic and anionic dyes, including real textile effluents.
• Zeta-potential and pH studies to understand binding mechanisms.
• Density Functional Theory (DFT) and Symmetry-Adapted Perturbation Theory (SAPT) calculations.

Main Results:

• TU-331 and TU-332 exhibit permanent microporosity and oxygen-rich anionic pockets.
• TU-331 demonstrated high adsorption capacity for Basic Green 1 and Methylene Blue (qmax = 302.7 and 280.0 mg g⁻¹).
• Selective adsorption of cationic dyes over anionic dyes was observed, with efficient regeneration (>99.5% capacity retention after 5 cycles).
• Successful decolorization of authentic industrial textile dyeing effluents was achieved.
• Computational analyses confirmed strong Coulombic attraction and π-stacking as key binding drivers for cationic dyes.

Conclusions:

• Reticular design of anionic microenvironments in COFs is a viable strategy for selective cationic dye capture.
• The developed COFs show promise for practical applications in treating industrial wastewater contaminated with textile dyes.
• This approach offers a blueprint for creating advanced materials for environmental remediation.