(A) study on porous organic cages (POCs) for efficient bromine vapor capture

Abstract

Adsorption-based bromine (Br2) capture systems are highly desirable for the safe storage and transportation of molecular bromine. In this study, we utilize nitrogen-containing porous organic cages (POCs) with large porosity and a high density of binding sites for volatile Br2 vapor capture. An imine-based POC (CC3-R) shows a static Br2 uptake capacity of 11.41 mmol·g-1 at 25°C while a tertiary amine-based POC (FT-RCC3) exhibits 10.08 mmol·g-1 under the same conditions. These values present their high capture performance compared with other MOFs which have been explored in previous studies. Adsorption mechanism of Br2 has been explained by experimentally identifying bromine species adsorbed at POCs and calculating their binding energies and Raman spectra. A high proportion of Br2 exists as polybromide states, resulting in the formation of charge-transfer complexes. This study demonstrates the importance of charge-transfer interactions between host materials and bromine molecules for achieving a highly efficient Br2 capture performance.