A graphene-like material, N2P6, is predicted, and its structural, mechanical, and electronic properties are investigated with first-principles methods. Herein, we focus on the gas sensitivity of the N2P6 nanosheet. The sensing performance of CO, CO2, H2O, H2S, N-2, NH3, NO, NO2, O-2, and SO2 is studied based on the metal-decorated N2P6 (M-N2P6). The results show that gas molecules can effectively be adsorbed on the M-N2P6 nanosheet and regulate the electronic and magnetic properties of the system. Among all these gas molecules, Li (Mg)-N2P6 exhibits strong affinity of NO (NO2) due to the strong interaction and charge exchange between gas molecules and the substrate. Moreover, horizontal biaxial strain and electric field can well regulate the adsorption energy and charge transfer of the NO@Li-N2P6 system, which imply that the adsorption performance and sensing capability can be enhanced by these measures and further signify that the Li-N2P6 nanosheet would be an excellent promising candidate for the efficient sensing of nitrogenous gas molecules. Our findings provide a new alternative of a NO efficient sensor and should be very useful for the adsorption or sensing mechanism of binary phosphorus nitrides in the future.