Contrasting the Role of Acidic and Basic Functional Groups on Iodine Capture Behavior of Post-Modified 2D Zn...

This work reports the effect of post-synthetic functionalization on iodine adsorption in a series of two-dimensional zinc coordination polymers (Zn-CP). Starting from a parent framework (Zn-CP, I), four derivatives were obtained through sequential modifications: solvent-free Zn-CP-df (II), ethylenediamine-functionalized Zn-CP-en (III), propane sultone-grafted Zn-CP-en-ps (IV), and 1,3-diaminopropane-cross-linked Zn-CP-dap (V). These transformations systematically tune the electronic environment of otherwise nonporous frameworks, enabling iodine uptake primarily through specific host-guest interactions rather than porosity. Among the series, Zn-CP-en (III) exhibits the highest iodine adsorption capacities, reaching 765.7 mg g^-1 in solution and 1963.1 mg g^-1 in the vapor phase, significantly exceeding those of the parent material (178.0 and 154.0 mg g^-1, respectively). The enhanced performance correlates with the presence of electron-donating amine functionalities, which facilitate charge-transfer interactions with iodine. In contrast, sulfur- and oxygen-containing modifications and framework cross-linking provide more moderate improvements, highlighting the dominant role of amine groups in governing adsorption efficiency. These results demonstrate that in nonporous 2D coordination networks, electronic structure engineering via functional group incorporation can outweigh conventional porosity-driven design principles. This study provides insight into the design of functional group-controlled adsorbents for iodine capture relevant to environmental and nuclear waste remediation.