Neutron total scattering measurements: Time-of-flight powder neutron diffraction experiments were conducted using the GEM diffractometer at the ISIS pulsed neutron and muon source, Rutherford Appleton Laboratory, UK . Powder samples of Y-CNx and R-CNx were loaded into 6 mm diameter cylindrical vanadium sample holders. Data collection consisted of ∼ 6 h duration (1000 μA h) data sets, acquired at 300 K for total scattering analysis. MantidPlot software was used for data reduction and normalisation. Total scattering data (covering a scattering range 0.5 < Q < 50 Å -1 when using the final processed files from the six GEM detector banks) were corrected and the pair distribution function was generated using the GUDRUN software. Transmission Electron Microscopy (TEM): The samples were dispersed in ethanol (supersonic bath) and drop-cast on holey carbon TEM grids. The TEM investigations were carried out using the chromatic (Cc) and spherical (Cs) aberrationcorrected Sub-Ångström Low-Voltage Electron (SALVE) microscope operating at 80 kV. Values for Cc and Cs were in the range of -10 µm to -20 µm. Imaging included diffraction pattern from selected areas and high resolution (HR) TEM, recorded on a Ceta 16M camera. Energyfiltered imaging exploiting absorption edges for elemental mapping was acquired on an Ultrascan 1000 XP camera using a Quantum ERS low-voltage Gatan imaging filter (GIF), attached to the SALVE microscope.