Efficient Iodine Capture and Release by a Triptycene and Tröger’s Base Cross-Linked Porous Organic Polymer

Abstract

A triptycene and Tröger’s base (TB) hybrid three-dimensional (3D) porous organic polymer (TP-TB-POP) was easily obtained by an acid-mediated condensation reaction between 2,6,14-triaminotriptycene (TAT) and methylal. The unique features of TP-TB-POP included its high surface area (SA_BET = 700 m²/g) and a nanoporous structure dominated by micropores. These were attributed to the presence of concave cavities associated with the “paddle-wheel-shaped” triptycene and “V-shaped and C2-symmetric” TB in the skeletal backbone of TP-TB-POP. The presence of ample arene rings (derived from triptycene) and basic nitrogen (sp³-hybridized) centers (derived from TB units) rendered TP-TB-POP a potential adsorbent for iodine vapors in the context of environmental remediation applications. A reasonably high iodine vapor uptake ability was recorded for TP-TB-POP (4.62 g of iodine/g of adsorbent), which was better than that of other adsorbents (reported to date) with both units (triptycene and TB) incorporated in their respective polymeric structures. Simple heating at elevated temperatures or even soaking in a benign solvent (like alcohol) at room temperature could release the trapped iodine effectively. The recycled adsorbent was also effective in trapping iodine and could be used for several cycles with moderately high adsorption capacities. Insights into the mechanistic aspects of iodine capture by TP-TB-POP were provided, supported by experimental data.