Synthesis and characterization of trimetallic (CuNiZn-PDC) MOF for the effective remediation of Rhodamine B dye

In the present study, we report the solvothermal synthesis of a novel trimetallic CuNiZn-PDC Metal Organic Framework (CuNiZn-PDC MOF) engineered for robust and efficient adsorption of Rhodamine B (RhB) dye from aqueous media. Comprehensive characterization, including SEM, XRD, FTIR, BET, TGA, zeta potential, EDX, and elemental mapping, confirmed its crystalline morphology, thermal stability up to 220 °C, and high specific surface area (529 m²/g) with pronounced microporosity. The material exhibits an average particle size of about 97 nm and an aggregate size of about 348 nm. Under optimized conditions (0.01 g adsorbent amount, 333 K, pH 8, 60 min contact time, 200 mg/L initial dye concentration), the MOF achieved > 93% RhB removal. Adsorption kinetics conformed to a pseudo-second-order model (R2 > 0.99), indicating chemisorption dominance, while equilibrium data fit the Langmuir isotherm (R2 = 0.99), yielding a maximum monolayer adsorption capacity of 395 mg/g at 333 K. Thermodynamic parameters (ΔH° =  + 11.77 kJ/mol, consistently negative ΔG° across the studied temperature range) denote an endothermic and spontaneous adsorption process. The adsorption mechanism likely arises from synergistic interactions of chemisorption, π-π stacking, pore-filling, electrostatic interactions, and hydrogen bonding. Impressively, the MOF retained 69% of its removal efficiency after seven adsorption-desorption cycles. These findings underscore the MOF's strong potential as a stable, high-capacity, and recyclable adsorbent for industrial wastewater treatment.