Abstract: Embodiments of the present disclosure describe a gas sensor comprising a gas-sensing material including a metal-organic framework with fcu topology and a substrate with a pair of electrodes proximate to the gas-sensing material, wherein the gas sensor is configured to detect toxic gas. Embodiments of the present disclosure further describe a method of detecting gas comprising contacting a gas sensor including a metal-organic framework with fcu topology with a gas/vapour composition including at least one toxic gas, capturing the at least one toxic gas from the fluid composition, and measuring an electrical property to detect a presence of the at least one toxic gas.