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

Abstract

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).

Recent progress in iodine capture by macrocycles and cages

“…A record adsorption capacity of 9.01 g g −1 was reported using SUPE-py-Imine-Cage , an amorphous imine cage, for the capture of KI/I 2 . 36 In contrast, the use of metallasupramolecular macrocycles and cages have received less attention with fewer studies reported, presumably due to the lower adsorption capacity and weaker stability. Effective adsorption usually requires more than 10 hours and slow adsorption kinetics remain to be a major problem for iodine capture with both types of discrete macrocycle and cage adsorbents.…”

“…11a and b). 36 Although both solid-state organic cages were evidenced to be nonporous and amorphous, they were able to effectively adsorb gaseous iodine with high uptake capacities (up to 6.02 g g À1 for the imine-cage and 4.63 g g À1 for the amine-cage) ascribed to the binding-induced adsorption mechanism (Fig. 11c).…”

“…Besides infinite porous materials, both macrocyclic and cage compounds, a class of intrinsically porous materials (IPMs) in the solid state were also proved to be good candidates for adsorbing radioactive iodine. [32][33][34][35][36][37] As a special class of adsorbents, they have cavities or sites for trapping iodine species via synergistic non-covalent interactions. Notably, there has been increasing interest in using macrocycles or cages having heteroatom-organic moieties for effective capture of iodine.…”

“…8 However, the great progress of macrocycle and cage-based adsorbents for iodine capture has been rarely analysed or reviewed. Some of these emerging iodine-capture materials have displayed uniqueness and superiority compared to these known porous materials, 32,36 vide infra.…”

Impact of Conformational Isomerism in Two Zn-MOFs on the Multimedia Incarceration of Iodine: In-Depth Experimental and Computational Assessments

“…In all the above-mentioned cases, surface as well as inclusion-based iodine transfer is likely to occur even with a less porous nature of the framework. 42 From the results of multiphase iodine transfer studies conducted with 1 and 2, it can be inferred that the uptake values in this work are better than many MOFs, POPs, and zeolites (Table S1) 21−36,43−52 For instance, the values of vapor phase iodine mass transfer for a T -SCNU-Z6 and a W -SCNU-Z6 are 2.05 g g −1 and 5.04 g g −1 , respectively, 43 whereas, those for HSB-W8 and Co-IPT-IBA are 2.32 g g −1 , 28 and 2.88 g g −1 , 34 respectively. Compared to this, ionic iodine transfer studies in the aqueous phase are rare.…”