The experimental discovery of two-dimensional penta-materials PdSe2 and PdPSe has boosted interest in their potential applications. In this work, we present a systematic ab initio study of the electronic properties of penta-PdSe2 and penta-PdPSe as sensors of molecules such as H2, CO, and NO, which are potentially dangerous gases. We find that Pd-based penta-materials are excellent sensors for NO molecules according to the adsorption energies and recovery times. Most importantly, they present a change from semiconducting to metallic behavior upon NO adsorption which points to their potential application for optoelectronic gas sensors © 2024 Elsevier B.V.