Coating the surface of interconnected CuO nanowire arrays with HKUST-1 nanocrystals via electrochemical oxidation.

Controlling the crystallization of Metal-Organic Frameworks (MOFs) at the nanoscale is currently challenging, and this hinders their utilization for multiple applications including photo(electro)chemistry and sensors. In this work, we show a synthetic protocol that enables the preparation of highly homogeneous CuO@MOF nanowires standing on a conductive support with extensive control over the crystallization of the MOF nanoparticles at the surface of the CuO nanowires. CuO nanowires were first prepared via templated electrodeposition, and then partially converted into the well-known Cu-MOF HKUST-1 by pulsed electrochemical oxidation. We show that the use of PVP as a capping agent during the electrochemical oxidation of CuO into HKUST-1 provides control over the growth of the MOF nanocrystals on the surface of the CuO nanowires, and that the size of the MOF crystals obtained can be tuned by changing the concentration of PVP dissolved in the electrolyte. In addition, we propose the use of benzoic acid as an alternative to achieve control over the size of the obtained MOF nanocrystals when the use of a capping agent should be avoided.