In contrast, while the combination of Zr 4+ and tricarboxylic acids can give 3D structures such as MOF-808, other syntheses with tritopic linkers using modulated solvothermal conditions can directly lead to 2D systems, typically containing Zr6 clusters (Figure ), that can be exfoliated into MONs (Figure ). Other relevant systems include tricarboxylate linked Hf12 clusters reported by Lin and co-workers, in which extended 4,4′,4′′-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl))tribenzoate linker bridges 12-connected Hf12 clusters. Wang and co-workers reported Zr-NiTCPP, where the Zr6 clusters are linked by tetratopic nickel-tetrakis(4-carboxyphenyl)porphyrin. Stock and co-workers reported CAU-45, possessing both Zr6 and Zr12 clusters linked by the 5-acetamidoisophthalic linker, which could be exfoliated by ultrasound assisted liquid phase exfoliation to access MONs. A 2D layered structure where Zr6 clusters are connected entirely by formate ligands has also been reported. Whether forming nanosheets directly from solution (bottom-up), or by exfoliating the layered materials using ultrasound energy to overcome the weak interlayer interactions (top-down), it is clear that judicious control of reaction conditions, including the use of modulators, is necessary to generate phase-pure MONs as opposed to three-dimensional counterparts. We have recently explored the phase space in Zr 4+ MOFs of the 4,4′-(ethyne-1,2-diyl)dibenzoate (EDB 2-) ligand, where the combined use of acetic acid as modulator and controlled amounts of water can favour the formation of an hcp topology phase with Zr12 clusters (GUF-12(Zr); GUF = Glasgow University Framework) over the more commonly observed fcu phase with Zr6 clusters.