For CNEO-DFT calculations, the same electronic exchange-correlation functional and electronic basis set are adopted for comparison. We only treated hydrogen nuclei quantum mechanically because heavier nuclei typically have smaller NQE than hydrogens. However, we note that a full quantum treatment is also possible with the CNEO framework. protons, which demonstrated accuracy and efficiency for vibrational analyses in previous studies. To explore the impacts of electron-proton correlations on molecular vibrations, particularly on proton transfer modes, the CNEO calculations were performed with the inclusion of the epc17-1 functional or the epc17-2 functional, and the results were compared with those at the no-epc level, which neglects all electron-proton correlation.