Selective capture of CO2 over N2 and CH4: B clusters and their size effects

Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO2 over N-2 and CH4 on planar-type B clusters, based on our previous finding of strong chemisorption of CO2 on the B10-13 planar and quasiplanar clusters. We consider the prototype B-8 and B-12 planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO2 can be separated from N-2 by selective binding to the B-12 cluster and not to the B-8 cluster. Selective adsorption of CO2 over CH4 at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N-2 on the planar-type B-36 cluster, we discuss the selectivity trend of CO2 adsorption over N-2 and CH4 with planar-cluster size, showing that it extends over sizes including B10-13 clusters and significantly larger.