Iodine radioisotopes, one of the major fission products in the nuclear industry, will cause widespread pollution due to their volatility when their inadvertent environmental release occurs. In this paper, a strategy for the efficient capture and real-time detection of iodine by amine-functionalized fluorescent conjugated mesoporous polymers (CMPs) is developed. CMPs are built up through a rigid skeleton and different flexible binding sites for iodine by the Sonogashira–Hagihara coupling reaction. Among them, CMP with N,N-diethylpropylamine (CMPN) shows outstanding capture ability for iodine vapor and dissolved iodine and also exhibits excellent stability against β- or γ-ray irradiation. Moreover, owing to the fluorescence quenching amplification of the conjugation skeleton, a CMPN-coated test paper enables highly sensitive detection of iodine even at 4 °C with a low vapor pressure of 16.8 Pa. To the best of our knowledge, CMPN with flexible and rigid binding sites gives the highest uptake values for iodine among all CMP-based materials reported to date, and it is the first functional material exhibiting the simultaneous adsorption and field detection of iodine vapor.