Electrospun Nanofiber Supported Nano/Mesoscale Covalent Organic Frameworks Boost Iodine Sorption

Covalent Organic Frameworks (COFs) are benchmark materials for iodine sorption, but their use has largely been confined to crystalline bulk forms. In this state, COFs face diffusion limitations leading to slow sorption kinetics. To address this, a series of [2 + 3] imine-linked COFs with varying particle sizes and morphologies (mesospheres, nanoflowers, and bulk) is synthesized. Reducing particle size (from 826 ± 48 to 412 ± 22 nm) and adding surface protrusions in COF mesospheres improved iodine adsorption capacity (7.6 to 8.5 g g⁻¹), kinetics (K_80%, 0.61 to 0.76 g g⁻¹ h⁻¹), and chemisorption efficiency. Notably, solvothermally synthesized (120 °C, 5 d) crystalline bulk COF with accessible porous surfaces exhibited faster kinetics (K_80%, 1.13 g g⁻¹ h⁻¹) than nano/mesoCOFs.This implies nano- and mesoCOFs exhibit surface aggregation that passivates their external binding sites and hinders iodine diffusion and mass transfer. To prevent this, morphologically controlled COF particles are immobilized onto electrospun polyacrylonitrile nanofibrous membranes via in situ growth strategy, creating a hierarchical structure that improved iodine diffusion pathways. This modification increased iodine sorption kinetics by 98%-153% and strengthened the charge-transfer process compared to COF powders.