Natural tea extract coated porous MOF nano/microparticles for highly enhanced and selective adsorption of cationic dyes from aqueous medium

A simple, sustainable method was developed for boosting the dye adsorption capability of porous metal organic frameworks (MOFs) by coating them with natural tea extract. Nano/microparticles of zinc-terephthalic acid (ZnTPA) MOFs exhibited only 40% rhodamine B (Rh B) dye adsorption. The dye adsorption capability was strongly enhanced (up to 95%) after coating with natural tea extract and highly selective cationic dye adsorption. The coating of multifunctional biomolecules onto the ZnTPA matrix was expected to facilitate strong intermolecular interaction between MOF surface and organic dyes, which contributed to strongly enhanced dye adsorption. ZnTPA/Tea MOFs not only exhibited enhanced dye adsorption but also showed high retention capability. The broader scope of tea extract coating methodology for cationic dye adsorption was also demonstrated using other MOFs matrix. The exhausted ZnTPA MOF was easily regenerated by sonication followed by re-dipping into tea extract. Tea extract coated ZnTPA MOFs was also used as column packing materials for removing cationic dyes by filtration. Thus, the present work reported a facile strategy for efficient cationic organic dyes removal from the aqueous medium.