Extended Data Fig. 6: TGA and IR spectroscopy of the pyridines in ZSM-5.
From: Atomic imaging of zeolite-confined single molecules by electron microscopy
a, TGA result of the pyridine/ZSM-5 sample. The sample stays at 120 °C (boiling point of pyridine) for 1 h to completely remove bulk or surface pyridines. The inset shows the peaks of pyridine desorption. At around 200 °C, most of the pyridines adsorbed mainly by van der Waals interactions were desorbed, whereas the remaining pyridines strongly bonding with the acid sites were also desorbed at over 300 °C. b, IR spectroscopy of protonated pyridines bonding with the acid sites at 200 and 350 °C. The peak at about 1,540 cm−1 indicates the N–H bonds in the protonated pyridines, which strongly interact with the Brønsted acid sites. This result shows that, in this temperature range, there are still some protonated pyridines (with near-horizontal configurations) confined in ZSM-5 channels.
