Abstarct: This research investigates the physical properties of surface adsorption of HCl, C2N2, and CNCl gas molecules on zigzag nanoribbons and nanosheets of β12 borophene using density functional theory (DFT). The results completely demonstrate the interaction between gas molecules and borophene. The sensing behavior of the borophene surface to the gas molecules has been investigated by studying the charge transfer, recovery time, adsorption energy, electronic band structure, and density of states (DOS). Changes in the electronic properties of borophene after the adsorption of gas molecules, confirm more the sensing properties of borophene towards adsorbed molecules. The results show that the adsorption of molecules on the nanosheet of β12 borophene is physisorption while on the nanoribbon is chemisorption. It is revealed that the gas sensor baxsed on β12 borophene nanosheet can be a suitable candidate for the detection of gas molecules.structures that have less adsorption energy and less recovery time are more suitable for the sensor. Since the adsorption of molecules on the nanosheet of β12 borophene is physisorption، they are more suitable for measuring gases