To study the interaction of closed-shell and open-shell gas molecules with the ZGNRs, we the prediction of the magnetic states of ZGNR by Pisani et al. The density of states of 4ZGNRH reveals that 4ZGNRH is a small band gap semiconductor with a band gap of 0.72 eV which is in good agreement with the previously reported value of 0.63 eV . Apart from the semiconducting nature of 4ZGNRH, the density of states reveals the spin-degenerate nature of energy levels, resulting in zero magnetic moments. Among the deposited gas molecules, the N 2 , CO, and CO 2 molecules are non-magnetic in nature. The N 2 has N -N bond length of 1.115Å which is in good agreement with the experimentally reported value of 1.098Å.