Mesoporous covalent organic frameworks with tailored hollow structure for superior iodine adsorption

Covalent organic frameworks (COFs), characterized by tunable porous structures and functional surfaces, have emerged as promising adsorbents for efficient separation and enrichment of radioactive iodine. However, the constructing of two-dimensional (2D) COFs that expose a high density of adsorption sites to achieve both high adsorption capacity and rapid kinetics remains a significant challenge. In this work, hollow COF (H-COF) were synthesized using a dynamic micellar assembly strategy in an emulsion system, employing Pluronic F127/P123 dual surfactants as a soft template. The H-COF exhibited hollow features, enhanced pore size distribution, pore capacity, and pore connectivity, providing more accessible pathways for accelerating iodine molecule diffusion. Impressively, the H-COF demonstrated a superior iodine adsorption capacity of 9.25 g·g −1 . In addition, the K 80% adsorption rate of H-COF was 0.93 g·g −1 ·h −1 , which is 9.3 times higher than that of conventional C-COF (0.10 g·g −1 ·h −1 ), highlighting its significantly faster adsorption kinetics. Mechanism analysis and DFT calculations revealed that polyiodide anions (I 3 − and I 5 − ) form through electron transfer from the imine groups in H-COF to iodine molecules, with a strong adsorption affinity for the imine bonds. This study presents an efficient iodine capture material and the potential of COFs in waste management.