Vapor Phase Installation of CpCo(CO)2 in MOF-808

Metal-organic frameworks (MOFs), including MOF-808 present an opportunity for vapor phase installation of reactive centers that may serve as uniform sites for precision catalysis. The mechanism of cobalt installation in MOF-808 through atomic layer deposition (ALD) upon CpCo(CO)₂ exposure is investigated through in situ FTIR spectroscopy complemented by density functional theory modeling. The role of subsequent H₂O exposure in the hydrolysis of carbonyl and cyclopentadienyl ligands to complete the installation is also investigated. In situ FTIR study reveals that upon exposure of CpCo(CO)₂ to MOF-808 at 115 °C, a long-lived, stable intermediate is formed that presents carbonyl stretching vibrations similar to the undissociated precursor that are attributed to multiple chemisorbed carbonyl complexes. In MOF-808, cobalt species are initially absorbed near the BTC linker rather than directly on the nodes, revealing the importance of non-covalent interactions in the installation process. DFT suggests that H₂O exposure promotes carbonyl elimination but leaves a cyclopentadienyl-capped cobalt that is more stable than the complete hydrolysis product. The simulations are consistent with cobalt installation in MOF-808 using CpCo(CO)₂ and H₂O at 115 °C and further consistent with the lack of ALD thin film deposition of cobalt oxide thin films on planar supports.