As partial delamination was observed during heating, GUF-14 hxl was first activated at 473 K for 16 h to aid the transition towards the hns phase, prior to ultrasound assisted liquid phase exfoliation which could be observed by powder X-ray diffraction (Figure ). Optimisation of the process showed exfoliation in water and ethanol to be more efficient than in acetonitrile, as evidenced by Tyndall scattering (Figure ). Atomic force microscopy (AFM, Figures and) imaging showed that water-based exfoliation produced thinner MONs of GUF-14, down to 1.3 nm, which is comparable to the van der Waals diameter of a single monolayer of Zr6 clusters, and so the following description of the GUF-14 hns phase refers to samples exfoliated in water.