Ultrasonic spray deposition as a new route to luminescent MOF film synthesis

The deposition of high-quality metal-organic framework (MOF) films is still challenging but offers potential applications in gas storage, catalysis, sensing, lighting, and solar energy harvesting. This work reports a single-step, simple, fast and inexpensive method for in situ synthesis and deposition of crystalline luminescent Tb-2(BDC)(3) (Tb = terbium) (BDC = 1,4-benzenedicarboxylate) MOF films using ultrasonic spray deposition on top of several types of substrates including glass slides, metal oxides films, filter paper, and polyimide sheets. The glass supported films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), profilometry, infrared (IR), and luminescence spectroscopies. As expected, the emission spectra present high-intensity characteristic emission bands of the sensitized terbium luminescence for all the films. Nevertheless, the temperature of the substrate, during deposition, plays a crucial role in the final structural and morphological characteristics of the MOFs, which in turn, dramatically modifies the excitation features. The MOF-film synthesis/deposition method here reported can be extended to other MOF structures and substrates.