Fig. 4. (A) Variable temperature ¹³C NMR spectra of the CPOS-5/¹³CO₂ sample under static conditions. The chemical shift anisotropic lineshape of solid CO₂, simulated starting from the main tensor components, is reported below for comparison. (B) Inclination angle (θ) of the CO₂ main-axis with respect to the reorientation-axis z about which the 90° (φ angle) jump occurs. (C) Screwing mechanism for CO₂ rototranslational dynamics in the channel: the 90° rotation angle of CO₂ projection onto the ab-plane and along the channel c-axis for CO₂ reorientation from one site to the next. (D) Overlay of the CO₂ positions along the channel as calculated by the DFT transition state method. (E) Helical trajectory of one CO₂ oxygen atom (red spheres) about the channel axis (blue bar). (F) Arrhenius plot of reorientational rates (k) versus the inverse of temperature. (G) Calculated energy profile for the rototranslation of CO₂ along the channel.