All-gas-phase synthesis of amino-functionalized UiO-66 thin films

Abstract

Thin films of metal–organic frameworks (MOFs) prepared using all-gas-phase techniques such as atomic/molecular layer deposition (ALD/MLD) are emerging due to their potential for enabling suitable applications. Their high and specific porosity enables their use as membranes for separations and as a basis for sensors in microelectronics, provided that films can be made. The properties of such MOF materials can be tuned by choosing linker molecules that are functionalized with a variety of chemical groups. However, thin films of these functionalised MOFs have so far been prepared through wet based chemistries, which are difficult to combine with microelectronics and high aspect ratio structures. We here report on the thin film deposition of amino-functionalised UiO-66 through an all-gas-phase ALD/MLD process. By using amino-functionalised linkers, modulation by acetic acid to control the stoichiometry of the deposited film was no longer required, as opposed to the case in which unmodified terephthalic acid was used as a linker. The growth and properties of the films were characterised using an in situ quartz crystal microbalance (QCM), spectroscopic ellipsometry (SE), grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR) and other techniques to obtain information on their growth dynamics and physical properties.