Highly efficient adsorption of iodine under ultrahigh pressure from aqueous solution

The radioactive nucleus of iodine is known to have debilitating effects on human health. Iodine exists in water in many forms, and it is difficult to accurately determine the iodine content in water. Hence, there are only a few reports on the adsorption of iodine from water. Here, we propose two porphyrin-based metal-organic frameworks (MOFs), denoted as PCN-223 and PCN-223-HPP (the latter treated under ultrahigh pressure), that can be used as adsorbents to effectively adsorb iodine from an aqueous environment. Both the MOFs had good chemical stability, thermal stability, and wet stability and could function at pressures up to 300 MPa. They could also be recycled several times. The specific surface area of PCN-223-HPP was 200 cm2 g−1 higher than that of PCN-223, which imparted an even better adsorption capacity to the former. The study of the adsorption mechanism revealed that the phenyl ring and nitrogen atom on the porphyrin together were responsible for the enhanced adsorption of iodine in aqueous solutions. The adsorption capacities of PCN-223 and PCN-223-HPP for I2 could reach as high as 1300 mg g−1.