Diketopyrrolopyrrole‐based Donor–Acceptor Covalent Organic Frameworks for Iodine Capture

Abstract

The recovery of radioactive iodine from nuclear waste and contaminated water sources is a critical environmental concern, which poses significant technical challenges. Herein, the study has demonstrated that tuning the electronic properties of diketopyrrolopyrrole‐based donor‐acceptor covalent organic frameworks (COFs) enhances iodine trapping, improves charge transport, and strengthens iodine interactions − establishing a structure‐property relationship. This tuning is achieved by synthesizing COFs with the diketopyrrolopyrrole‐based linker 3,6‐bis(4‐(1,3‐dioxolan‐2‐yl)phenyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (DKP) in combination with either the electron acceptor 4,4′,4″‐(1,3,5‐triazine‐2,4,6‐triyl)trianiline (TTT‐DKP) or the electron donor N₁,N₁‐bis(4‐aminophenyl)benzene‐1,4‐diamine (TAPA‐DKP) linkers. These COFs, with abundant sorption sites, thermal and chemical stability, and optimized pore environments, efficiently bind iodine in the vapor and solution phases. The TAPA‐DKP COF, containing electron‐donating moieties, showed a high iodine uptake of 3.52 g/g, exceeding the 2.81 g/g of the electron‐deficient TTT‐DKP in the vapor phase, both following pseudo‐second‐order kinetics. Density functional theory (DFT) calculations reveal adsorption sites showing that TAPA‐DKP COF binds I₂ more effectively via its electron‐rich moieties, highlighting the role of electronic property modulation in iodine adsorption.