[Display omitted] • H 2 O, NH 3 and NO 2 prefer to be adsorbed on the h-BN part of a G/h-BN/G/h-BN/G multi-heterostructure. • While H 2 O is weakly adsorbed, NH 3 and NO 2 show moderate and strong adsorptions, respectively. • The proposed device is not sensitive to humidity, while it shows high sensitivity toward NH 3 and NO 2 molecules. • NH 3 and NO 2 molecules change the device current in two opposite directions, a selective behavior of the proposed device toward these two molecules. Two dimensional nanomaterials are promising for gas sensing applications due to their large surface to volume ratio. Recent studies show that the sensitivity of pristine graphene, the most prominent two-dimensional material, can be improved by several methods such as doping, decoration and combination with other two-dimensional materials. In the present work a two-dimensional graphene/h-BN multi-heterostructure, in the form of G/h-BN/G/h-BN/G, is proposed for gas sensing applications, which is expected to outperform pristine graphene devices. The adsorption energies and charge transfer for H 2 O, NH 3 and NO 2 molecules are investigated at the density functional level of theory. The presence of two insulating h-BN layers induces potential barriers for charge carriers and changes the current mechanism to the quantum tunneling regime, which is highly sensitive to the modulation of the potential barrier due to the adsorbed molecules. A first principles method based on non-equilibrium Green's function formalism is employed for the calculation of the device current in various environments. The proposed device shows little sensitivity toward H 2 O but it is very sensitive toward NH 3 and NO 2. Moreover, NO 2 adsorption increases the device current, while NH 3 adsorption reduces the current, a property which can result in a selective sensing of these two gas molecules. [ABSTRACT FROM AUTHOR]