Multipath Bromine Capture by a Metal–Organic Framework and Its Applications

Abstract

Bromine and its compounds are of great importance in industrial and agricultural processes. Developing new methods for capturing and separating elemental bromine from brine or seawater is attractive and challenging. Here, we demonstrated that a highly stable Cd-MOF allows for reversible bromine uptake from either vapor or a brine phase at ambient temperature. Fast adsorption for a low concentration of Br₂ indicated its potential application in bromine capture from seawater. Recycling experiments testified to the reusability of Cd-MOF as a bromine capture material. The adsorption mechanism was elucidated for the first time by single-crystal structural analysis. Three adsorption pathways, including physically adsorbed Br₂, anion exchanged Br₅^– and chemically generated N–Br bonds, synergistically captured bromine into the framework. The strong Br···Br interactions between Br₂ molecules and Br^– anions and N–Br bonds play an important role in fixing three Br₂ molecules in the framework. Bromination reactions for six aromatic substrates under ambient conditions were also carried out by this Br-loaded material, and the results showed a higher monobromination yield for methylphenols.