In this present work, the investigation was carried out using density functional theory (DFT) for the dissociation of noxious gas molecules such as carbon and nitrogen-based molecules (CO, CO2, N2, NH3, NO, and NO2) on a pentagonal two-dimensional beryllium diphosphide (BeP2). The pentagonal BeP2 monolayer has a similar band structure as graphene. Here, some carbon and nitrogen-based noxious gases such as CO, CO2, N2, NH3, NO, and NO2 with Van der Waals (vdW) interaction behave like physisorbed, while strong covalent (Be-O) interactions of O2 on BeP2 formed chemisorption. Due to the chemisorption of O2 gas molecules, the bandgap at Dirac point at P-site on BeP2 opens. While CO, CO2, N2, NO, and NO2 are dissociated at the C-site, only CO, N2, and NO are dissociated at the P-site. Beryllium diphosphide's band-gap shifts resulting from interactions with CO, N2, and O2 molecules are just 6%, 12.1%, and 22.2%, respectively, meaning that the BeP2 material has a moderate and high sensitivity towards CO, N2, and O2 molecules. BeP2 appears to be a potential catalyst for the dissociation of CO, CO2, N2, NO, NO2, and O2 gas molecules, which is even more interesting.