Porous Materials

Porous Silsesquioxane–Imine Frameworks (PSIF)

The efficient capture and storage of radioactive iodine (¹²⁹I or ¹³¹I), which can be formed during nuclear energy generation or storage of nuclear waste, is of paramount importance. Herein we present highly efficient aerogels for reversible iodine capture, namely Porous Silsesquioxane-Imine Frameworks (PSIF), constructed by a condensation of octa(3-aminopropyl)silsesquioxane cage compound (OAS-POSS) and selected multitopic aldehydes. The resulting PSIFs are permanently porous (Brunauer-Emmet-Teller (BET) surface areas up to 473 m²/g), thermally stable and present a combination of micro- and macropores in their structures. The presence of a high number of imine functional groups in combination with silsesquioxane cores results in extremely high I₂ 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 4 times while maintaining 94% I₂ uptake capacity. Kinetic studies of I₂ desorption show two strong binding sites with apparent activation energies of 77.0 kJ/mol and 89.0 kJ/mol. These energies are considerably higher than the enthalpy of sublimation of bulk I₂.

See: ACS Appl. Mater. Interfaces, 2018, 23, 19964-19973