Fabrication of 3D Oriented MOF Micropatterns with Anisotropic Fluorescent Properties

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, we design a patternable oriented MOF film: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylic ligand (Br2BDC) into a copper-based MOF Cu2L2DABCO (L=BDC/Br2BDC). The lithographed samples act as a diffraction grating upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, we demonstrate the alignment of the dye in the MOF. By controlling the functional response to light, this MOF patterning protocol could be used for the microfabrication of optical components for photonic devices.