Density functional theory was employed to investigate the interaction between a monolayer of B3C2N3 and potential biomarkers of liver cancer present in exhaled breath. The focus of our study was specifically on 1- Octen-3-ol, limonene, hexanal, 2-pentanone, methanol, and decane. Furthermore, we examined the most stable arrangement of these biomarkers on the B3C2N3 monolayer and compared it to the adsorption of four interfering molecules commonly found in exhaled human breath, namely N2, O2, CO2, and H2O. The selectivity of the B3C2N3 nanosheet for these biomarkers is confirmed, even in the presence of interfering species. The nanosheet surface demonstrates both electronic and φ-type sensor properties when detecting the methanol biomarker. The B3C2N3 nanosheet exhibits favorable adsorption energy and φ-type sensor properties, along with an appropriate recovery time, when exposed to the 1-Octen-3-ol and limonene biomarkers. Finally, we propose the B3C2N3 nanosheet as a reusable sensor for the early diagnosis of liver cancer based on the biomarkers detection through the analysis of patients’ exhaled breath