Utilization of Physical Anisotropy in Metal-Organic Frameworks via Postsynthetic Alignment Control with Liquid Crystal

Metal-organicframeworks (MOFs) represent crystalline materialsconstructed from combinations of metal and organic units to oftenyield anisotropic porous structures and physical properties. Postsyntheticmethods to align the MOF crystals in bulk remain scarce yet tremendouslyimportant to fully utilize their structure-driven intrinsic properties.Herein, we present an unprecedented composite of liquid crystals (LCs)and MOFs and demonstrate the use of nematic LCs to dynamically controlthe orientation of MOF crystals with exceptional order parameters(as high as 0.965). Unique patterns formed through a facile multidirectionalalignment of MOF crystals exhibit polarized fluorescence with thefluorescence intensity of a pattern dependent on the angle of a polarizer,offering potential use in various optical applications such as anoptical security label. Further, the alignment mechanism indicatesthat the method is applicable to numerous combinations of MOFs andLCs, which include UV polymerizable LC monomers used to fabricatefree-standing composite films.