Facile Microwave-Assisted Synthesis of 2D Imine-Linked Covalent Organic Frameworks for Exceptional Iodine Capture.

Abstract

Covalent organic frameworks (COFs) have emerged as auspicious porous adsorbents for radioiodine capture. However, their conventional solvothermal synthesis demands multiday synthetic times and anaerobic conditions, largely hampering their practical use. To tackle these challenges, we present a facile microwave-assisted synthesis of 2D imine-linked COFs, Mw-TFB-BD-X, (X = -CH3 and -OCH3) under air within just 1 h. The resultant COFs possessed higher crystallinity, better yields, and more uniform morphology than their solvothermal counterparts. Remarkably, Mw-TFB-BD-CH3 and Mw-TFB-BD-OCH3 exhibited exceptional iodine adsorption capacities of 7.83 g g-1 and 7.05 g g-1, respectively, placing them among the best-performing COF adsorbents for static iodine vapor capture. Moreover, Mw-TFB-BD-CH3 and Mw-TFB-BD-OCH3 can be reused 5 times with no apparent loss in the adsorption capacity. The exceptionally high iodine adsorption capacities and excellent reusability of COFs were mainly attributed to their uniform spherical morphology and enhanced chemical stability due to the in-built electron-donating groups, despite their low surface areas. This work establishes a benchmark for developing advanced iodine adsorbents that combine fast kinetics, high capacity, excellent reusability, and facile rapid synthesis, a set of appealing features that remain challenging to merge in COF adsorbents so far.