(648d) Fe-MOF-525 Films Grown in Situ for Carbon Dioxide Conversion

Metal organic frameworks have been utilized for a range of decarbonization technologies, including carbon capture, storage, and transformation processes. Most of these studies have been performed with MOFs that are created as powders and then shaped into the desired modules. However, it would be ideal to grow films of MOFs as thin films on substrates such as membranes. The advantages of this in-situ growth would be better control over optimal MOF thickness, and to utilize technologies that are capable of rapid deposition, and large-area scalability.

Solution shearing, a meniscus-guided coating process, can create large-area metal–organic framework (MOF) thin films rapidly, which can lead to the formation of uniform membranes for separations or thin films for sensing and catalysis applications. Although previous work has shown that solution shearing can render MOF thin films, examples have been limited to a few prototypical systems, such as HKUST-1, Cu-HHTP, and UiO-66. Here, we expand on the applicability of solution shearing by making thin films of NU-901, a zirconium-based MOF. We study how the NU-901 thin film properties (i.e., crystallinity, surface coverage, and thickness) can be controlled as a function of substrate temperature and linker concentration. High fractional surface coverage of small-area (∼1 cm²) NU-901 thin films (0.88 ± 0.06) is achieved on a glass substrate for all conditions after one blade pass, while a low to moderate fractional surface coverage (0.73 ± 0.18) is obtained for large-area (∼5 cm²) NU-901 thin films. The crystallinity of NU-901 crystals increases with temperature and decreases with linker concentration. On the other hand, the adjusted thickness of NU-901 thin films increases with both increasing temperature and linker concentration. We also extend the solution shearing technique to synthesize MOF-525 thin films on a transparent conductive oxide that are useful for electrocatalysis. We show that Fe-metalated MOF-525 films can reduce CO₂ to CO, which has implications for CO₂ capture and utilization. The demonstration of thin film formation of NU-901 and MOF-525 using solution shearing on a wide range of substrates will be highly useful for implementing these MOFs in sensing and catalytic applications.