Design and Synthesis of Stable Sp2-Carbon-Linked Two-Dimensional Conjugated Covalent Organic Framework for Efficient Capture of Iodine

The ingenious design of sp2-carbon-linked fully π-conjugated covalent organic frameworks (sp2-c-COFs) with a periodic pore structure and high chemical stability, is vital. However, this remains a significant challenge owing to the poor reversibility of the coupling reactions. Here two novel isoreticular crystalline and highly porous two-dimensional (2D) sp2-c-COFs (COF-p-NEU1 and COF-p-NEU2) are designed and synthesized via a base-catalyzed Knoevenagel polycondensation reaction based on the [C2 + C3] topology diagram. As-prepared polycrystalline COF-p-NEU1 (with 1,3,5-tris(p-formylphenyl)benzene) and COF-p-NEU2 (with 1,3,5‐tris‐(4‐formylphenyl) triazine) exhibit long-range ordered structures, well-defined nanochannels, and favorable chemical stable, which endow the promising capture performance of COF materials. Meanwhile, the two sp2-c-COF can provide abundant functional units to promote the capture of I2 due to introducing mass nitrogen species into the building block. Therefore, the two nitrogen-rich sp2-c-COFs exhibit a high iodine uptake capacity for iodine vapor and iodine in cyclohexane with 4.58 g g-1 and for 1.31 g g-1 COF-p-NEU1 and 5.87 g g-1 and 1.51 g g-1 for COF-p-NEU2 at 348 K. The results of this study provide a potential path for the design and synthesis of novel sp2-c-COFs materials with high chemical stability and demonstrate the high potential of sp2-c-COF for the capture of radioactive contaminants.