Hafnium-Based Metal-Organic Framework UiO-66 as an Inkjet-Printed Ferroelectric Material
Metal-organic frameworks (MOFs) have emerged as an extensive class of promising materials, comprised of metal ions linked by organic ligands. The synthetic material has generated significant interest and has been utilized in a wide range of applications including sensing, drug delivery, gas storage and separation, and catalysis. Their versatility can be attributed to their many favorable characteristics such as tunable structure, polymeric composition, ultrahigh porosity, functionalization, robustness, and biocompatibility. One specific MOF structure of interest is hafnium-based MOF UiO-66, which possesses extraordinary properties such as superior stability in addition to exhibiting piezoelectric and ferroelectric responses. Moreover, the advancement of additive manufacturing technology and the drive for printed electronics has led to a growing need for functional inks. This research examines hafnium-based MOF UiO-66 more closely by first completing a solvothermal reticular synthesis. Subsequently, material characterization is conducted through various means such as X-Ray Diffraction (XRD) analysis and Fourier-Transform Infrared (FT-IR) spectroscopy. Next, the MOF material was formulated into a functional ink using a two-solvent system based on DI water and DMF. Once a viable functional ink was complete, the material was printed via inkjet deposition. MOF UiO-66 (Hf) printed samples are examined and measured through scanning electron microscopy (SEM) and piezoresponse force microscopy (PFM). Piezoelectric behavior and partial ferroelectric behavior are confirmed in inkjet-printed hafnium-based MOF UiO-66. This research progresses our understanding of implementing a two-solvent system to formulate a ferroelectric functional ink that is effectively deposited via inkjet printing for potential incorporation into electronic circuits for sensing applications.