A Trimming-π Strategy for Constructing Functional Conductive Metal-Organic Frameworks Using Metalloporphyrazine Units

Developing functional metal-organic frameworks (MOFs) with high electrical conductivity is crucial for their applications as advanced electronic materials. In this work, we for the first time construct a new family of functional and highly conductive MOFs using metalloporphyrazine (MPz) ligands based on a trimming-π concept via cutting the benzene ring from molecular metallopthalocynine (MPc). The deprotonation-after-coordination synthetic method affords crystalline MPz-Cu-NH MOFs with square lattices. Four-point probe conductivity measurements reveal the high room temperature electrical conductivity of MPz-based MOFs ranging from 3.5×10^-2 to 1.3×10^-1 S cm^-1, two orders of magnitude higher than the MPc-based MOF counterparts. Temperature-dependent conductivity measurements and electronic band structure analysis demonstrate ultra-small activation energies with potential metallic conducting behavior for the MPz-Cu-NH MOFs. Encapsulation of the aromatic guest molecules with different electron-donating and -withdrawing features allows the conductivity modulation of the CuPz-Cu-NH in a wide range spanning two orders of magnitude. These conductive MPz-Cu-NH MOFs with built-in MPz functional units exhibit MPz identity-dependent sensing performance, and realize highly sensitive detection of NH₃ and NO₂ using a low driving voltage of 0.1 V.