Bimetallic ZIF-8 from Hydroxide Double Salts for Efficient Cu²⁺ Removal in Wastewater

Metal-organic frameworks (MOFs) hold significant potential for applications in gas adsorption and separation, catalysis, chemical sensing, and drug delivery. Zeolitic imidazolate frameworks (ZIFs) are a type of MOF composed of metal ions and imidazolate ligands, structurally similar to zeolite structures. ZIF-8, a widely studied ZIF material, is composed of zinc ions (Zn²⁺) and 2-methylimidazole as fundamental building blocks featuring unique porous structures, a high specific surface area, and excellent thermal and chemical stability. This study introduces a rapid room-temperature synthesis method for bimetallic ZIF-8 through the hydroxide double salt (HDS) precursor. Various characterization techniques confirmed that the synthesized bimetallic ZIF-8 exhibits uniform particle size and high crystallinity. Experimental results indicate that the HDS precursor provides numerous active sites, facilitating rapid nucleation and resulting in uniformly sized bimetallic ZIF-8 particles. By optimizing the ultrasonic time of HDS, the concentration of 2-methylimidazole, and the reaction time, the synthesis conditions were refined, producing bimetallic ZIF-8 particles with an average size of 135.0 nm and a minimum polydispersity index (PDI) of 0.024. Additionally, the copper ion adsorption performance was evaluated, with the synthesized bimetallic ZIF-8 showing the highest adsorption capacity of 1196.82 mg/g at pH 6, demonstrating its effectiveness in heavy metal removal.