Hydrazine-functionalized Al-MOF with pore-size regulation for selective iodine capture in NO2-containing off-gas

To address the competitive adsorption of NO 2 during gaseous iodine capture from spent fuel reprocessing off-gas, a hydrazine-functionalized aluminum-based metal-organic framework, CAU-10-N 2 H 3 , was constructed based on CAU-10. Considering the difference in kinetic diameter between I 2 and NO 2 , hydrazine functionalization was employed to synergistically regulate the pore size and pore electronic environment. After the introduction of -N 2 H 3 , the median pore size decreased from 0.6174 to 0.5186 nm, and the NO 2 uptake was reduced by 42.91%. Meanwhile, the introduced electron-rich -N 2 H 3 groups strengthened the interaction between the framework and iodine species, leading to adsorption capacities of 551.99 and 155.93 mg·g −1 for I 2 and CH 3 I, respectively, at 150 °C. Dynamic breakthrough experiments further showed that the I 2 adsorption capacity was only slightly affected by NO 2 , decreasing from 259.3 mg·g −1 under N 2 to 218.8 mg·g −1 under 5% NO 2 . Mechanistic analyses revealed that the introduced -N 2 H 3 groups promoted the conversion of I 2 into polyiodide species, thereby strengthening both iodine adsorption and fixation. These results demonstrate that introducing electron-rich functional groups to synergistically regulate pore size and pore environment is an effective strategy for improving the selective iodine capture performance of Al-MOFs in complex spent fuel reprocessing off-gas.