Light-Active Anisotropic 2D MOF Heterojunctions for Fingerprint-Like Sensing of VOCs

Traditional metal oxide semiconductor (MOS) and metal-organic framework (MOF) sensors typically rely on a single response signal, which is easily influenced by concentration and unable to effectively distinguish structurally similar volatile organic compounds (VOCs) at room temperature. To overcome these limitations, we constructed a p-n heterojunction platform by integrating a 2D semiconductor MOF, Cu-HHTP_[001], onto patterned Au/Si interdigitated electrodes. This architecture promotes effective charge separation, enabling a light-assisted sensing response within seconds. In situ surface-enhanced infrared spectroscopy (SEIRAS) combined with ex situ structural characterization analyses reveal that in-plane coordination between copper carboxylates and HHTP ligands directs the [001]-oriented growth of Cu-HHTP, forming a polycrystalline in-plane structure with anisotropic conductivity. This structure exhibits reversible framework oscillations during gas adsorption-desorption, transducing molecular interactions into a characteristic electrical signal. Leveraging this mechanism, we engineered a multichannel sensor that generates concentration-independent fingerprint-like response, enabling qualitative VOC identification and opening a pathway to advanced gas recognition.