Pressure is an under-explored variable in the crystal chemistry of microporous materials. Depending on the pressure-generating conditions and the size of the pore-opening of the material, pressure can be used as a probe to vary the volume in a constant chemistry 1,2 or as a function of the size of pressure-transmitting medium. 3,4 To the best of our knowledge, pressure has not yet been applied in the investigation of the influence of extra-framework cations on the flexibility of the molecular sieve frameworks.