Fig. 2: Structural characterization of [2]rotaxane 1 and MINs.

a–c Partial ¹H NMR spectra (CDCl₃, 400 MHz, 293 K) of (a) B21C7 wheel, (b) [2]rotaxane 1, and (c) secondary ammonium salt axle. d FTIR spectra of MIN-4, [2]rotaxane 1, DODT, and PETMP. e Swelling ratio histogram of MIN-4 in different solvents.