Benzoxazine-linked porous organic networks for effective iodine capture

This study presents, for the first time, the investigation of a benzoxazine-linked porous organic network (BPON) for iodine capture. BPON was synthesized through the Mannich condensation of paraformaldehyde, melamine, and phloroglucinol. The porous structure and heteroatom-rich skeleton of BPON make it a promising adsorbent platform for iodine capture. BPON demonstrated an effective iodine capture capability in the vapour phase (3.32 g g⁻¹) and an impressive uptake capacity in the aqueous phase (2.80 g g⁻¹ capacity, 90.4% removal efficiency in 12 hours). To investigate the effect of curing on iodine capture, BPON was thermally cured to prepare thermally cured benzoxazine-linked porous organic networks (cBPONs) at three different temperatures: 200, 250, and 300 °C. cBPONs demonstrated an iodine capture capacity of up to 2.20 g g⁻¹ and 1.67 g g⁻¹ for vapour and aqueous phases, respectively. The iodine capture mechanism of BPON was investigated using various ex situ analyses, including Fourier transform infrared (FT-IR), Raman spectra, and X-ray photoelectron spectra (XPS). Structural analysis and theoretical calculations indicated the formation of a charge-transfer complex upon iodine capture, leading to the generation of polyiodide species. This study demonstrates the potential of BPONs for iodine capture and paves the way for developing new polymeric adsorbents for capturing iodine from air and water.