Copper MOG for efficient anionic dyes adsorption and tunable transformation into single crystal MOF

A thermo-reversible copper (II) metal-organic gel (MOG), formed with a hexapyridine triphenylene ligand (3py) in dimethyl sulfoxide (DMSO) (minimum gelation concentration: 0.6 w/v%), was synthesized and structurally characterized via SEM, TEM, NMR, BET, TGA, T gel experiments and rheological studies. Conversion of MOG to MOF was demonstrated, where single crystal XRD showed that it was a 3-D metal-organic framework (MOF) with 1-D porous channels throughout the structure along c axis. The resulting xerogel efficiently adsorbed anionic dyes (Rose Bengal, Eosin Y, Methyl Orange), with maximum adsorption capacities of 734.2, 751.6, and 302.5 mg/g, respectively, following Langmuir isotherms and pseudo-first-order kinetics. Mechanistic studies, employing FTIR and zeta potential analyses, demonstrated that adsorption was primarily driven by weak intramolecular interaction such as π-π stacking, alongside electrostatic interaction and hydrogen bonding. The significant charge differential between the positively charged xerogel and anionic dyes underscored the dominance of electrostatic attraction. This study elucidates the synthesis and adsorption efficacy of a novel MOG, offering potential for wastewater remediation. • Thermo-reversible copper MOG with highly conjugated hexapyridine triphenylene ligand. • MOG was evaluated as an adsorbent for the adsorption of anionic dyes. • Adsorption mechanisms are attributed to electrostatic interaction, π–π stacking, and H-bonding. • Solvent dependent conversion of amorphous MOG to crystalline MOF.