  Using density-functional theory (DFT), we investigate the selectivity of
adsorption of CO2 over N2 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 B8 and B12 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 N2
by selective binding to the B12 cluster and not to the B8 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 N2 on the planar-type B36
cluster, we discuss the selectivity trend of CO2 adsorption over N2 and CH4
with planar-cluster size, showing that it extends over sizes including B10-13
clusters and significantly larger.
