Self-assembly and optoelectronic properties of isoreticular MOF nanocrystals

Abstract

Self-assembly behaviour and optoelectronic properties of IRMOF-8 nanocrystals have been studied for the first time. Utilizing a rapid and simple self-assembly directed solvothermal process, microstructures of an interpenetrated analogue of IRMOF-8 was prepared and fully characterized. The elemental composition analysis reveals that the structural formula is to be Zn4O(NDC)3, confirming the original IRMOF-8 structural formula. The powder XRD analysis along with simulated XRD traces of two known IRMOF-8 analogues (IRMOF-8 and INT-IRMOF-8 A) reveals that the crystal structure of IRMOF-8 microstructures follows the primitive cubic (pcu) unit cell topology as the two-fold interpenetrated IRMOF-8. The selective area electron diffraction (SAED) pattern further supports the interpenetrating network with off-sets layer-by-layer arrangement of NDC units. The UV–vis spectra of nanostructures show the naphthalene absorption with a pronounced excitonic transition absorption at 374 nm and 380 nm for Zn4O clusters in solution and thin films, respectively. The optical band gap of 2.84 eV and the characteristic linker-based luminescence evidence that microstructures show excellent semiconducting properties. The thin films of microstructures exhibit an electrical conductivity of 3.98 × 10−2 S/cm at room temperature.