Methanol Oxidation Catalyzed by Copper Nanoclusters Incorporated in Vacuum-Deposited HKUST-1 Thin Films

Metal-organic framework (MOF) thin films allow the unique properties of MOFs to be incorporated into membranes and microelectronic devices and also permit studies of catalysis employing powerful ultrahigh vacuum (UHV) surface chemical probes. Here, we report on methanol oxidation catalysis by copper nanoclusters (4-6 and 8-12 nm) incorporated within a HKUST-1 thin film (similar to 100 nm thick) investigated using UHV temperature-programmed desorption methods. In particular, the Cu-HKUST-1 film with 4-6 nm copper clusters selectively oxidizes methanol molecules to formaldehyde, while the Cu-HKUST-1 film (similar to 100 nm thick) with 8-12 nm copper clusters more strongly oxidizes the methanol to generate not only formaldehyde, but also CO2 caused by the formation of formate species. This study demonstrates the potential to control the Cu nanoparticle size during the vacuum deposition of HKUST-1 thin films and how incorporated Cu clusters of different sizes affect the methanol oxidation catalytic activity under vacuum-controlled conditions.