Synthesis and Structure of a 2D Cadmium‐Based MOF for Efficient Malachite Green Adsorption

ABSTRACT Malachite green (MG), a commonly used cationic organic dye, is bio‐refractory. Although various removal methods offer opportunities for its degradation, many of these approaches still have limitations. For example, intermediate products generated during photocatalytic degradation may cause secondary pollution, and traditional porous materials suffer from insufficient adsorption stability. Here, we report the rational design and synthesis of a Cd‐MOF . This material incorporates a pyrazole carboxylic acid ligand—an azo ligand that combines an azo group, a high pKa pyrazole heterocycle, and a carboxyl coordinating group. This strategy endows the material with both a stable framework and accessible adsorption sites. At room temperature and atmospheric pressure, the adsorption removal efficiency of MG dye reached 91.06%. The adsorption process was simulated using a quasi‐second‐order kinetic model, intraparticle diffusion model, and the Langmuir model to explain the material's adsorption behavior toward MG, respectively. This work highlights the application value of azo ligands as precursors in the design of adsorbent structures. A stable Cd‐MOF was successfully synthesized using pyrazole carboxylic acid‐functionalized azo ligands. The resultant Cd‐MOF possesses a stable framework and abundant accessible adsorption sites, which exhibit excellent adsorption performance for malachite green dye with a maximum adsorption capacity of 1347 mg·g −1 at room temperature and atmospheric pressure. The adsorption isotherm and kinetic studies demonstrate that the MG adsorption process conforms to the Langmuir model, pseudo‐second‐order kinetic model and intraparticle diffusion model.