Optimized Congo Red Dye Adsorption Using ZnCuCr-Based MOF for Sustainable Wastewater Treatment

This study presents the synthesis of a novel trimetallic ZnCuCr-TpIm metal–organic framework (MOF) via a solvothermal method, yielding cubic crystals of 300–500 nm. The integration of Zn, Cu, and Cr metal centers enhances the MOF’s adsorption efficiency and structural stability, distinguishing it from conventional MOFs. The material achieves a high Congo red dye removal efficiency (96.5%) under optimal conditions: 40 mg adsorbent dosage, 55 °C, pH 6–7, and a 60 min contact time. Kinetic analysis reveals that the adsorption follows a pseudo-second-order model (R2 > 0.999), indicating chemisorption as the rate-limiting step, while equilibrium data align with the Langmuir isotherm model (R2 = 0.998), confirming a maximum adsorption capacity of 325 mg/g. FTIR and XRD analyses confirm strong interactions between the dye molecules and the MOF framework while preserving its crystalline structure. The ZnCuCr-TpIm MOF demonstrated exceptional stability, retaining 95% of its surface area after 72 h and maintaining over 90% adsorption efficiency after five reuse cycles, with minimal metal ion leaching (<1.2 ppm). The material also exhibited high resilience under varying pH, salinity, and simulated wastewater conditions, underscoring its potential for long-term and sustainable dye removal applications. These findings highlight the synergistic advantages of the trimetallic MOF, making it a promising candidate for efficient and stable wastewater treatment.