Theoretical Screening and Experimental Synthesis of Ultrahigh-Iodine Capture Covalent Organic Frameworks.

Radioactive materials of nuclear waste would be hazardous to human health such as the reproductive and metabolic system. How to design a radioactive material adsorbent quickly and efficiently is still a great challenge. In this study, a strategy for the efficient design of a high-potential radioactive iodine uptake adsorbent by theoretical screening is proposed. The following experiments which use covalent organic frameworks (COFs) as demonstration have great agreement with the theoretical screening prediction. Three screened COFs show ultrahigh iodine adsorption, which reaches up to 6.4 g/g (640% in mass) in vapor and 99.9 mg/g in solution, owing to the pore size and the functional groups in COFs.

C[double bond, length as m-dash]N linked covalent organic framework for the efficient adsorption of iodine in vapor and solution.

Volatile nuclear wastes, such as iodine, have received worldwide attention because it poses risks to public safety and pollutes the environment. The efficient capture of radioactive iodine is of vital importance for the safe utilization of nuclear power. Herein, we report a series of stable covalent organic framework (COF) materials with high efficiency to capture radioactive iodine species. Results indicated that all COFs showed high iodine adsorption, which reached up to 5.82 g g-1 in vapor and 99.9 mg g-1 in solution, suggesting that all COFs can be an effective potential adsorbent for the removal of iodine. Furthermore, all COFs are renewable due to the excellent recycling performance. Moreover, all COFs are suitable for large-scale synthesis at room temperature, which have potential for practical applications. Theoretical calculations were also performed to analyze the relationship between iodine molecules and COFs, offering mechanisms underlying the potent adsorption abilities of COFs.

Easily Constructed Imine-Bonded COFs for Iodine Capture at Ambient Temperature.

Volatile radionuclides generated during the nuclear fission process, such as iodine, pose risks to public safety and cause the threat of environmental pollution. Covalent organic framework (COF) materials have a controlled pore structure and a large specific surface area and thus demonstrate great opportunities in the field of radioactive iodine adsorption. However, the harsh synthetic conditions and the weak binding capability toward iodine have significantly restricted the applications of COFs in iodine adsorption. Here, we demonstrate a facile way to prepare a series of stable C-N-linked COFs with high efficiency to capture radioactive iodine species. Large-scale synthesis can be conducted by the aldol condensation reaction at room temperature. The resulting COFs have a large surface area and a strong resistance to acid, base, and water. Moreover, all types of COFs show high iodine adsorption, up to 2.6 g/g (260% in mass), owing to the large surface area and the functional groups in COFs. They not only absorb conventional I2 molecular but also ionic state (I3 - and I+) iodine species. Theoretical calculations are further performed to understand the relationship between different iodine species and the functional groups of all COFs, offering the mechanisms underlying the potent adsorption abilities of COFs.