Nonporous amorphous superadsorbents for highly effective and selective adsorption of iodine in water

Adsorbents widely utilized for environmental remediation, water purification, and gas storage have been usually reported to be either porous or crystalline materials. In this contribution, we report the synthesis of two covalent organic superphane cages, that are utilized as the nonporous amorphous superadsorbents for aqueous iodine adsorption with the record-breaking iodine adsorption capability and selectivity. In the static adsorption system, the cages exhibit iodine uptake capacity of up to 8.41 g g-1 in I2 aqueous solution and 9.01 g g-1 in I3- (KI/I2) aqueous solution, respectively, even in the presence of a large excess of competing anions. In the dynamic flow-through experiment, the aqueous iodine adsorption capability for I2 and I3- can reach up to 3.59 and 5.79 g g-1, respectively. Moreover, these two superphane cages are able to remove trace iodine in aqueous media from ppm level (5.0 ppm) down to ppb level concentration (as low as 11 ppb). Based on a binding-induced adsorption mechanism, such nonporous amorphous molecular materials prove superior to all existing porous adsorbents. This study can open up a new avenue for development of state-of-the-art adsorption materials for practical uses with conceptionally new nonporous amorphous superadsorbents (NAS).