A zwitterionic pyridine-carboxylate Cd(II) MOF for dual-function environmental remediation: Iodine capture and selective Cr2O72− luminescent sensing

A new Cd(II)-based MOF, namely, {[Cd(CIPA)₂]·2DMF·H₂O}_n (cc, HCIPA = 1-(4-carboxyphenyl)pyridin-1-ium-4-yl)(pyridin-4-yl)amide), was constructed on the basis of a new zwitterionic pyridine-carboxylate ligand. Single-crystal X-ray analysis revealed that Cd-CIPA has a 3D supramolecular framework with bilayer 2D networks stabilized by weak π‒π interactions, featuring 1D channels occupied by solvent molecules. By removing the guest molecules, the iodine adsorption property of activated Cd-CIPA was studied. This material has an iodine vapor adsorption capacity of 3.2 g/g, which is attributed to strong charge‒transfer interactions between iodine and N/O-containing moieties in the framework. Additionally, Cd-CIPA functions as a selective fluorescent sensor for aqueous Cr₂O₇²⁻ detection, where quenching is governed primarily by the inner filter effect. This work highlights the dual functionality of zwitterionic ligand-derived MOFs for simultaneous pollutant capture and sensing.