Synergistic of Nitrogen Cross-Linking Modification, Fiber Body Preparation, and the Incorporation of Covalent Organic Framework (COF) Result in a Considerable Enhancement of Iodine Capture by Lignin

To fully leverage the potential of lignin for capturing radioactive iodine, this study first involved cross-linking lignin using the nitrogen-rich cross-linking agent diethylenetriamine to obtain a modified product. Subsequently, we employed electrospinning technology to transform the modified product into a fibrous, thereby enhancing lignin's solvent stability and broadening its application scope. Notably, we introduced COF growth sites, para-phenylenediamine (Pa), into the spinning solution. Finally, the Pa-containing nanofibers were reacted with the COF growth ligand 1,3,5-tri(4-formylphenyl)benzene. This reaction facilitated the self-growth of TFB-DB COF on the fiber surface, ultimately yielding lignin nanofibers embedded with TFB-DB COF (L/TFP(X)NF). L/TFP(X)NF is regarded as a reusable iodine-capturing material. L/TFP(1.2)NF exhibited the highest performance, capturing approximately 475.0 mg/g, 4451.7 mg/g and 2191.2 mg/g of iodine in steam, n-hexane solution and aqueous solution, respectively. This study significantly enhanced the iodine capture efficiency of lignin through the synergistic effects of nitrogen cross-linking modification, fiber preparation, and COFs.