Disentangling genuine biomarker responses from oxygen-mediated backgrounds in photoactivated conductive MOF thin films

Conductive metal–organic frameworks (cMOFs) are promising materials for room-temperature gas sensing; however, the interplay among photoactivation, ambient oxygen, and target-gas adsorption remains poorly understood. Here, we report nanoscale conductive Cu-HHTT thin films fabricated via a layer-by-layer assembly approach and systematically investigate their sensing behavior toward 3-hydroxy-2-butanone (3H2B). Under 365 nm illumination, the films exhibit only a weak electrical response to 3 ppm 3H2B in a stable air background, while achieving an experimentally determined detection limit of 30 ppb. In contrast, switching between air and N₂ produces a substantially larger electrical response. Further analysis reveals a pronounced atmosphere-dependent background contribution to the photoinduced electrical signal, which can complicate the accurate identification of the genuine gas response. This work establishes an evaluation strategy for distinguishing genuine VOC responses from oxygen-mediated background signals, providing a useful framework for performance assessment and mechanistic understanding of photoactivated cMOFs gas sensors.