On-Demand Tunable Electrical Conductance Anisotropy in a MOF-Polymer Composite

Property optimization through orientation control of metal-organic framework (MOF) crystals that exhibit anisotropic crystal structures continues to garner tremendous interest. Herein, an electric field is utilized to post-synthetically control the orientation of conductive layered Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) crystals dispersed in an electronically insulating poly(ethylene glycol) diacrylate (PEGDA) oligomer matrix. Optical and electrical measurements are performed to investigate the impact of the electric field on the alignment of Cu₃(HHTP)₂ crystals and the formation of aggregated microstructures, which leads to an ≈5000-fold increase in the conductivity of the composite. Notably, the composite thin-films containing aligned Cu₃(HHTP)₂ crystals exhibit significant conductivity of ≈10^-3 S cm^-1 despite the low concentration (≈1 wt.%) of conductive Cu₃(HHTP)₂. The use of an electric field to align Cu₃(HHTP)₂ crystals can rapidly generate various desired patterns that exhibit on-demand tunable collective charge transport anisotropy. The findings provide valuable insights toward the manipulation and utilization of conductive MOFs with anisotropic crystal structures for various applications such as adhesive electrical interconnects and microelectronics.