Metal–Organic Frameworks-Based Fabry−Pérot Cavity Encapsulated TiO₂ Nanoparticles for Selective Chemical Sensing

This paper reports a Fabry−Pérot (F–P) cavity constructed by metal–organic frameworks (MOFs) encapsulated with TiO₂ nanoparticles that can achieve selective sensing of chemicals. The MOFs-based F–P cavity is fabricated by sequentially spray-coating TiO₂ in HKUST-1 thin films through a layer-by-layer deposition strategy. The bandwidth of the cavity is tuned over a broad range by adjusting the thickness and refractive index of the HKUST-1⊃TiO₂ thin films with controllable TiO₂ size and concentration. Selective sensing of chemical vapors is demonstrated on the HKUST-1⊃TiO₂ cavities which are attributed to enhanced interaction between hydroxyl groups on the surface of TiO₂ and the specific oxygen-containing analytes. In addition, molecule dynamics simulation and infrared absorption spectrum characterization are conducted to elucidate the mechanism of enhanced sensing properties. Homogeneous encapsulation of functional guest pieces with smaller sizes in MOF films contributes to specific physical–chemical properties that benefit their device applications in optical communication and chemical sensing.