Fig. 2: A stack plot of 31P MAS NMR spectra of the sample. | Nature Communications

Fig. 2: A stack plot of 31P MAS NMR spectra of the sample.

From: Polyphosphonate covalent organic frameworks

Fig. 2

a GTUB5 and GTUB5 annealed at (b) 100 °C, c 120 °C, d 140 °C, e 160 °C, f 180 °C, g 200 °C, h 220 °C and (i) 270 °C under vacuum. The measurements were performed with a rotor with 2.5 mm outer diameter spinning at 20 kHz (a–h) or 14.3 kHz (i) under a 7.04 T magnet. The box chart indicates the range of the isotropic 31P NMR chemical shift values of hydrogenmonophosphonates (top, Q0)31, that of phosphonates with a single bridging O atom including diphosphonates (middle, Q1)32, and of phosphonates with two bridging O atoms (ring/chain) attached to the observed P-atom (bottom, Q2)33,34. The black circles refer to literature values (Supplementary Table 4), the colored symbols refer to the isotropic chemical shift values observed for GTUB5 and GTUB5 annealed at 220 °C and 270 °C.

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