Exploration of tetra-branched multiple-site SO2 capture materials†
We designed a series of tetra-branched anionic structures centered with Al for more efficient SO2 capture. By using the home-made configuration search program coupled with electronic structure calculations, we have systematically explored the large reaction space consisting of these anions, cations, and SO2 molecules. Unique insertion structures of the reaction complexes featuring a SO2 molecule inserted into a branch were found to be prevalent and sometimes to be the ground states. Cations can either enhance or compress the anion–SO2 interactions, highly depending on the anion, as they have multiple ways to interact with anions and SO2 molecules. According to the calculated sequential SO2 binding energies (with the cation effect included), [Al(Im)4]− is expected to be the best among the designed structures for reversible SO2 capture. This approach can be easily extended to design and screen sorbents for other acidic gases.