The toxic gases emitted from industrial production have caused significant damage to the environment and human health, necessitating efficient gas sensors for their detection and removal. In this work, first-principles calculations are employed to investigate the potential application of diamanes for high-performance toxic gas sensors. The results show that nine gas molecules (CO, CO 2 , NO, NO 2 , NH 3 , SO 2 , N 2 , O 2 , and H 2 O) are physisorbed on pristine diamane by weak van der Waals interactions. After introducing H/F defects, diamane can effectively capture specific toxic gases (CO, NO, NO 2 , and SO 2 ) in the presence of interfering gases (N 2 , O 2 , and H 2 O), suggesting excellent selectivity and antiinterference ability. Orbital hybridization and significant charge redistribution between gas molecules and defective diamane dominate the enhanced adsorbate−substrate interactions. More importantly, the high sensitivity and good reversibility of defective diamane for detecting CO, NO, and SO 2 molecules enable its reuse as a superior resistance-type gas sensor. Our calculations provide valuable insights into the potential of defective diamane for detecting toxic gases and shed light on the practical application of novel carbon-based materials in the gas-sensing field.