Raman spectroscopy combined with electrochemistry, illustrated at the top of Fig. , can elucidate redox states. Figure shows the Raman spectra of the Cu-triazole MOF biased at electrochemical potentials in the range of -3 to 3 V in OMIM-Cl. It is evident that the spectral response changes reversibly as the potential is varied stepwise from 3 V to -3 V, and then back to 3 V (from bottom to top in Fig. ). At the very bottom it shows the Raman spectrum for an as-grown crystal measured in air that exhibits prominent peaks at 1001 and 1302 cm -1 . The spectrum at 3 V (second from the bottom) exhibits the same peaks. The most intense peak at 1302 cm -1 can be attributed to the ring stretching mode of the triazole.