Formation Mechanism and Enhanced Iodine Capture of Copper-Based Aluminum-Oxo Cluster Bimetallic Organic Frameworks

Bimetal-organic frameworks (biMOFs) are emerging as promising porous materials for radioactive iodine capture. However, the rational construction of biMOFs with heterometallic secondary building units (SBUs) remains a significant synthetic challenge due to sensitivity to reaction parameters such as ligand concentration, ionic speciation, and solvent effects. Here, we have investigated these influences in detail and elucidated the formation mechanism of a novel copper-based biMOF (CuAlOC-58) constructed from Cu²⁺ ions and aluminum-oxo clusters (AlOCs) as the SBUs. The successful assembly relies on a synergistic coordination strategy, leveraging the "hard-hard" interaction between Al³⁺ and carboxylate oxygen and the 'borderline-borderline' interaction between Cu²⁺ and pyridine nitrogen. Moreover, we further validated the critical role of trace water molecules in the solvent system, which are essential for mediating the solvation of copper ions and enabling their structural integration. The incorporation of copper not only links the AlOC units to form special micropores but also exposes a greater number of active adsorption sites. Consequently, CuAlOC-58 exhibits superior iodine adsorption kinetics and a remarkable maximum adsorption capacity of 613.00 mg/g. This work provides deep insights into the controlled synthesis of complex heterometallic MOFs and their iodine capture applications.