The growth of thin films of porous metal organic frameworks (MOFs) are highly desirable because the unique characteristics of MOFs could then be incorporated into micro-electronic devices, sensors, and membranes. Here we report a new thin film growth method for highly oriented HKUST-1 under vacuum without the use of liquid solvents. Employing a layer-by-layer (LBL) growth method in vacuum, we deposit the H3BTC ligand via a chemical vapor deposition process and Cu from a physical vapor deposition step, sequentially. Based on H3BTC supramolecular structures, we grow the thin film of HKUST-1 by depositing Cu after each H3BTC deposition. The transition of Cu0 to Cu2+ by forming paddle-wheel units of HKUST-1 is confirmed by XPS, and is facilitated by O2 and H2O (co-exposed), while there is no indication of copper oxide formation. These HKUST-1 thin films are highly oriented to the (220) plane of HKUST-1, and the thickness of the films linearly increases depending upon the number of LBL cycles, as determined by AFM. We separately adsorbed H2O on a 100 nm thick film of HKUST-1 at 120 K, 200 K, and 240 K under high vacuum, and observe the existence of strongly bound H2O molecules absorbed within the HKUST-1 film, which predominantly desorb at ~398 K.

Solvent-free growth of oriented HKUST-1 thin films under vacuum

2019 Fall National Meeting

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