Herein, we firstly develop porous organic cage (POC) as an efficient platform for highly effective radioactive iodine capture under industrial operating conditions (typically ≥ 150 °C, ≤ 150 ppmv of I2). Due to the highly dispersed and readily accessible binding sites as well as sufficient accommodating space, the constructed NKPOC‐DT‐(I‐)Me (NKPOC = Nankai porous organic cage) demonstrates a record‐high I2 uptake capacity of 48.35 wt% and extraordinary adsorption capacity of unit ionic site (~1.62) at 150 °C and 150 ppmv of I2. The I2 capacity is 3.5, 1.6, and 1.3 times higher than industrial silver‐based adsorbents Ag@MOR and benchmark materials of TGDM and 4F‐iCOF‐TpBpy‐I‐ under the same conditions. Furthermore, NKPOC‐DT‐(I‐)Me exhibits remarkable adsorption kinetics (k1 = 0.013 min−1), which is 1.2 and 1.6 times higher than TGDM and 4F‐iCOF‐TpBpy‐I‐ under the identical conditions. NKPOC‐DT‐(I‐)Me thus sets a new benchmark for industrial radioactive I2 adsorbents. This work not only provides a new insight for effectively enhancing the adsorption capacity of unit functional sites, but also advances POC as an efficient platform for radioiodine capture in industry.