Composites of polyaniline (PANI) and Zr-based metal–organic
frameworks (MOFs), UiO-66 and UiO-66-NH2, were synthesized
by the oxidative polymerization of aniline in the presence of MOF
templates with the MOF content in the resulting materials (78.2 and
86.7 wt %, respectively) close to the theoretical value (91.5 wt %).
Scanning electron microscopy and transmission electron microscopy
showed that the morphology of the composites was set by the morphology
of the MOFs, whose structure was mostly preserved after the synthesis,
based on the X-ray diffraction data. Vibrational and NMR spectroscopies
pointed out that MOFs participate in the protonation of PANI and conducting
polymer chains were grafted to amino groups of UiO-66-NH2. Unlike PANI-UiO-66, cyclic voltammograms of PANI-UiO-66-NH2showed a well-resolved redox peak at around ≈0 V,
pointing at the pseudocapacitive behavior. The gravimetric capacitance
of PANI-UiO-66-NH2, normalized per mass of the active material,
was also found to be higher compared to that of pristine PANI (79.8
and 50.5 F g–1, respectively, at 5 mV s–1). The introduction of MOFs into the composites with PANI significantly
improved the cycling stability of the materials over 1000 cycles compared
to the pristine conducting polymer, with the residual gravimetric
capacitance being ≥100 and 77%, respectively. Thus, the electrochemical
performance of the prepared PANI-MOF composites makes them attractive
materials for application in energy storage.