Alignment controllable synthesis of MOF films: From Cu(OH)2 nanowire array to highly oriented Cu-MOF film

This work applies a quasi-epitaxial growth method to synthesize the highly oriented Cu-MOF film with the Cu(OH)2 nanowire arrays. The Cu(OH)2 nanowires with high aspect ratio were first synthesized via an optimization of the reactant concentration, then deposited and arrayed with the gravity assistance on an ITO substrate via a fluid-assisted technique. Based on the template with the Cu(OH)2 nanowire arrays, the Cu-MOF film was synthesized via the displacement reaction at room temperature. By optimizing the number of times and the flow velocity of the fluid-assisted technique, a Cu-MOF film with a thickness of above 0.9 ​μm and a roughness below 84.73 ​nm was obtained. The calculated crystallographic preferred orientation (CPO) index of the (00l) direction showed that the film had a strong c-axis orientation. Furthermore, the fluorescence spectra of the DMASP dyes aligned in the channels of this oriented Cu-MOF film exhibited a polarization ratio of about 2.83.