Linkage Engineering in Porous Aromatic Frameworks for Recyclable Iodine Adsorption and Applications in...

Recyclable capture and release of iodine are crucial for environmental issues and the sustainable utilization of iodine. Herein, we present a linkage-engineering strategy in porous aromatic frameworks (PAFs) to regulate iodine adsorption and release. Three PAFs with identical tetraphenylmethane-triazine building blocks but featuring distinct linkages-carbon-carbon single bond (TPM-TTA), secondary amine (TPM-NTTA), and alkynyl group (TPM-ETTA)-demonstrate that the linkage type significantly influences framework properties, including structural defects, porosity, and hydrophilicity, which in turn determine iodine uptake capacity, adsorption kinetics, and recyclability. Among them, TPM-TTA exhibits the highest surface area of 1086 m² g^-1, and achieves the highest iodine uptake capacities from vapor (3.27 g g^-1), saturated iodine aqueous solution (2.45 g g^-1), and KI/I₂ aqueous solution (6.93 g g^-1), along with rapid, near-quantitative release in methanol. Notably, iodine-loaded TPM-TTA serves as a recyclable solid iodine reservoir, facilitating efficient iodine-mediated organic transformations, including β-iodoetherification of alkenes and α-sulfenylation of carbonyls, with broad substrate scope and excellent yields. This study highlights the rational linkage design as a powerful strategy to develop recyclable iodine adsorbents and further expands the practical applications of iodine-loaded materials in organic synthesis.