The tenets of coordination chemistry enable researchers to design and develop nanostructured materials based on metal-organic frameworks (MOFs). Herein, for the first time, we applied the Schiff base system to MOF derivatives as a strategy for the heteroatom introduction into carbon-based metal oxides toward electrochromic applications. The presented Ni-MOF thin films based on Schiff base ligands were prepared by a facile and economical reductive electrosynthesis approach, facilitating the scalable fabrication of large-size electrochromic films derived from MOFs. After the pyrolysis, the desired N-doped NiO@C (N-C@NiO) films can achieve a high cycling stability (500 cycles with 7% contrast attenuation) and coloration efficiency (80.18 cm2/C) via different pyrolysis procedures. In addition, the one-step fabricated N-C@NiO shows an excellent ability of contrast modulation (68%@580 nm) with merely 3.6% transmittance at the colored state. These improvements in electrochromic properties are attributed to hierarchical porous heterostructures and influenced by the N/C ratio and C-N bonding configuration, indicating that N-C@NiO systems derived from Schiff base MOFs are promising for low-transmittance displays.
Keywords: Schiff base; electrochromism; heteroatom; metal−organic frameworks; reductive electrosynthesis.