Rapid and recyclable removal of Congo Red dye using mesoporous Zinc-based metal organic framework

Abstract

Metal-organic frameworks (MOFs) have emerged as advanced adsorbent materials in wastewater purification because of their high porosity, tunable structure, and exceptional surface area. In the present work, a zinc-based MOF (ZMOF) was prepared via a solvothermal method using zinc nitrate and terephthalic acid. The structural and surface properties of ZMOF were characterized using XRD, FTIR, SEM, BET surface area analysis, XPS, and zeta potential measurements. These results proved that the crystalline mesoporous framework exhibited a surface area of 1188.43 m²g^-1, pore radius of 1.68 nm, homogeneous morphology, and a moderately negative surface charge of −11.54 mV, which could enhance electrostatic interaction with anionic dyes. ZMOF exhibited outstanding adsorption performance. About 92% CR could be removed within 3 min at a concentration of 3.48 mg/L. After being reused four times, 64% efficiency could still be maintained. The kinetic modeling showed that the adsorption fits well to the PSO model with R² = 0.989, indicating a chemisorption-dominant process driven by coordination and electrostatic interaction between Zn²⁺ centers and functional groups of CR. The post-adsorption analyses of XRD, FTIR, SEM, XPS, and zeta potential indicated structural stability with a dual contribution of physisorption and chemisorption. These results demonstrate rapid, recyclable and stable performance of ZMOF toward dye removal from wastewater, showcasing its great potential as a sustainable adsorbent for large-scale treatments.