Reversible iodine vapor capture using bipyridine-based covalent triazine framework: Experimental and computational investigations

Abstract To address the environmental issues arising from the emission of radiotoxic iodine from nuclear waste streams, developing high-capacity and recyclable adsorbents is urgently demanded. In this study, a nitrogen-rich covalent-triazine framework (CTF-bpy) was synthesized through the ionothermal synthetic method and was used as a reusable adsorbent to capture iodine vapor for sequential cycles. The obtained CTF-bpy adsorbent showed ultrahigh iodine vapor capture capacity of 4.52 g.g−1 at 90 °C and atmospheric pressure, which ranks among the highest values reported to date. CTF-bpy could be simply recycled by washing and heating while preserving above 89.6% of its initial iodine capture capacity after five consecutive cycles, demonstrating its excellent structural stability. Assessment of the adsorption kinetics of the iodine vapor through the fractal-like pseudo-first-order (FL-PFO) kinetic model revealed that the diffusion through micropores was the rate-controlling mechanism. Moreover, the density functional theory (DFT) calculations further demonstrated the significance of the surface's basicity and aromaticity of the structure in efficiently capturing the iodine species. This study may shed light on designing and developing novel adsorbents suitable for solving one of the main environmental issues.