(248b) Electrocatalytic Reduction of Carbon Dioxide Using Metal-Organic Framework Thin Films

Carbon dioxide (CO₂) emission and concentration have been rising sharply since 1960s and if no preventive measurements are taken, the average global temperature could increase by more than 2 ^oC by the end of 2050. One possible way to mitigate the CO₂ emissions is to capture the atmospheric CO₂ and convert it into useful chemicals like carbon monoxide (CO). Electrocatalytic reduction of CO₂ into CO is a promising technology; however, deposition of catalyst on the electrode surface could result in particle aggregation, which could reduce the surface area available for catalysis. To overcome this issue, metal-organic frameworks (MOFs), porous crystalline materials composed of inorganic metal clusters and organic linker, are utilized as a scaffold to deposit well-separated catalysts molecules inside MOF pores to prevent aggregation and enhance surface area for catalysis. To use MOFs as a scaffold, thin films of MOFs are required. Nonetheless, existing methods to synthesize MOF thin films are time consuming and not easily scalable. Herein, we employ meniscus-guided coating called, solution shearing to fabricate MOF thin films. Solution shearing is a facile and scalable technique to produce large-area MOF thin films within minutes. We show the formation of MOF-525 films using solution shearing for the first time. In solution shearing, we inject MOF-525 precursor solution between a moving blade and a heated substrate. As the solvent evaporates, the MOF-525 crystals are formed and blade movement spreads the MOF-525 crystals uniformly on the substrate resulting in a MOF-525 thin film. We create MOF-525 films over an area of 1.5 cm² within 10 to 15 minutes. Powder X-ray diffraction (PXRD) patterns confirm the formation of MOF-525 crystals and scanning electron microscopy (SEM) shows the crystals are spherical-shaped. Afterward, we incorporated Fe as a catalyst inside MOF-525 crystals (termed as Fe-MOF-525). MOF-525 structure remains the same after incorporating Fe as confirmed by PXRD pattern and SEM image. Preliminary cyclic voltammetry (CV) data shows that Fe-MOF-525 films are electrocatalytically active toward CO₂ reduction. Currently, we are optimizing the synthesis conditions to maximize the yield and selectivity of CO. This work motivates the use of solution shearing to synthesize various MOF thin films for target applications.