Enhanced Stability of Metal-Organic Frameworks Via Plasma-Enhanced Chemical Vapor Deposition

Metal organic frameworks (MOFs) have become a leading class of porous materials for applications such as gas storage, catalysis, and toxic gas removal.  Yet, many interesting MOFs, especially those with coordinatively unsaturated metal centers and/or carboxylate linkers, are prone to degradation from moisture, making them less useful for ambient operations.  Through treatment of Cu₃BTC₂ MOF with plasma-enhanced chemical vapor deposition of perfluorohexane, we have sufficiently modified the structure such that it is more-resistant to moisture degradation.  Characterization with ¹³F NMR shows the presence of perfluoro groups within the pore structure, reducing water-clustering and increasing the metal-oxo bond stability.  Ammonia breakthrough studies indicate that, not only does the material retain its high ammonia capacity post-treatment, but the stability actually increases retention and capacity under low and high humidity conditions.  Further work is currently being explored on a variety of plasma/MOF systems to study the effects of perfluoro compound and metal-linker behavior.