Porous Silsesquioxane-Imine Frameworks as Highly Efficient Adsorbents for Cooperative Iodine Capture

The efficient capture and storage of radioactive iodine (I-129 or I-131), which can be formed during nuclear energy generation or nuclear waste storage, is of paramount importance. Herein, we present highly efficient aerogels for reversible iodine capture, namely, porous silsesquioxane- imine frameworks (PSIFs), constructed by condensation of octa(3-aminopropypsilsesquioxane cage compound and selected multitopic aldehydes. The resulting PSIFs are permanently porous (Brunauer-Emmet-Teller surface areas up to 574 m(2)/g), thermally stable, and present a combination of micro-, meso-, and macropores in their structures. The presence of a large number of imine functional groups in combination with silsesquioxane cores results in extremely high I-2 affinity with uptake capacities up to 485 wt %, which is the highest reported to date. Porous properties can be controlled by the strut length and rigidity of linkers. In addition, PSIF-1a could be recycled at least four times while maintaining 94% I-2 uptake capacity. Kinetic studies of I-2 desorption show two strong binding sites with apparent activation energies of 77.0 and 89.0 kJ/mol. These energies are considerably higher than the enthalpy of sublimation of bulk I-2.