Iodine sequestration using cyclophosphazene based inorganic-organic hybrid nanoporous materials: Role of surface functionality and pore size distribution

Cyclophosphazene based inorganic-organic hybrid nanoporous materials having triazine and pyrrolic functionality named as HNM-1 and CHNM-1, respectively, with varying nitrogen content, hierarchical pore size and high specific surface area have been explored for iodine sequestration application. The presence of electron rich functionality in the HNM-1 and CHNM-1 provides a large number of active sites for the adsorption of iodine. Maximum gravimetric iodine capture capacity of 223 and 120 wt% were estimated in HNM-1 and CHNM-1 specimens, respectively, under fuel processing condition i.e. 75 °C and ambient pressure. Moreover, both the specimens have shown very good iodine release behavior in organic solvents. The recyclability of HNM-1 and CHNM-1 for iodine sorption has shown the retention of adsorption capacity by 80 and 86%, respectively, even after five cycles. The iodine sorption both in vapor as well as solution phases is greatly influenced by the nitrogen content and pore size distribution of the framework materials.