Constructing nitrogen-rich clover-like covalent organic frameworks for effective iodine capture
Radioactive iodine isotopes (129I, 131I) generated during nuclear fuel reprocessing pose severe long-term environmental and public health hazards, with 129I exhibiting a half-life of 1.57×10^7 years. Covalent organic frameworks (COFs) have emerged as promising adsorbents for iodine capture due to their tunable porosity and chemical stability. This study reports the rational design and synthesis of two nitrogen-rich COFs, DFPT-COF and DFPB-COF, featuring well-defined clover-like nanochannels constructed from meta-position monomers. The clover-like morphology enhances specific surface area and provides multidimensional diffusion pathways for iodine species. DFPT-COF achieves an exceptional iodine vapor capture capacity of 5.58 g g−1, outperforming DFPB-COF, attributable to its larger specific surface area and abundant nitrogen adsorption sites. Adsorption kinetics for liquid iodine follow a pseudo-second-order model, and the isotherm data conform to the Langmuir model, indicating monolayer chemisorption. DFPT-COF demonstrates excellent regenerative adsorption performance over multiple cycles, underscoring its potential as a sustainable and efficient green adsorbent for iodine in nuclear waste management. This work establishes a structure-property relationship linking meta-position monomer geometry to clover-like morphology and enhanced iodine capture, offering a design strategy for next-generation radioiodine sorbents.