  Using first-principles calculations, we report structural and electronic
properties of CO, NO$_2$, and NO molecular adsorption on $\beta$-In$_2$Se$_3$
in comparison to a previous study on alpha-phase. Analysis and comparison of
adsorption energies and extent of charge transfer indicates
$\beta$-In$_2$Se$_3$ to be selective in detecting gas molecules. We found NO
molecules acting as charge donor whereas CO and NO2 molecules as charge
acceptors, respectively, experiencing physisorption in all cases. Owing to
enhanced adsorption, faster desorption and improved selectivity of the gas
molecules discussed in detail, we conclude $\beta$-In$_2$Se$_3$ to be a
superior gas sensing material ideal for chemoresistive-type gas sensing
applications.
