Click chemistry for efficient preparation of cage-based covalent organic frameworks featuring high iodine uptake for lithium-iodine battery

Abstract

The rapid growth of nuclear energy has led to the annual production of thousands of tons of high-level liquid waste, with radioactive iodine being a major and dangerous component. However, efficient capture and conversion of radioactive iodine remains a critical challenge in the field of materials science. Here, to address the issue, we constructed two nitrogen-rich cage-based covalent organic frameworks (Cage-COF-TB and Cage-COF-NTBA) via rapid amino-alkyne click polymerization between amine-functionalized organic cages and alkyne monomers, affording crystalline β-ketoenamine-linked frameworks within 6 h. Both Cage-COFs exhibit exceptional iodine vapor uptake capacities, with values of 6.35 and 4.65 g g⁻¹, respectively. Upon iodine loading, the electronic conductivity of the Cage-COFs increases significantly, enabling their application as cathode materials in lithium-iodine batteries. The I₂@Cage-COF-NTBA electrode delivers an initial discharge capacity of 147 mAh g⁻¹ at 0.3 A g⁻¹ and exhibits long-term cycling stability with an ultralow capacity fading rate of 0.018% per cycle over 1000 cycles at 1 A g⁻¹. This work presents the first β-ketoenamine-linked Cage-COF platform for high-temperature iodine vapor capture and energy conversion, offering a promising strategy for the immobilization and reutilization of radioactive iodine from high-level nuclear waste.