To address the significant energy pollution created by nuclear waste and the environmental catastrophe resulting from rapid industrial expansion, electronic-rich materials are widely developed and applied. However, the stability and reproducibility of the material limit its practical application. Therefore, the development of highly stable electron-rich adsorbents remains a great challenge. Herein, we report two highly stable thiophene-based COFs (JLNU-308 and JLNU-309) for iodine capture. Thiophene groups enhance electron-rich interactions with iodine, boosting adsorption capacity. Both COFs exhibit strong iodine adsorption and stability. Notably, JLNU-309 achieves rapid adsorption within 50 h, reaching 3.840 g g-1 capacity. In addition, theoretical calculations unequivocally demonstrate that in addition to the influence of thiophene groups, the superior adsorption capability of JLNU-309 can be attributed to the robust interaction between the adsorbed iodine and the many triazine nitrogen-rich adsorption sites that are evenly dispersed throughout the pore. Therefore, this study offers a method for designing and developing electron-rich COFs with high stability.