Metal–organic nanosheets formed via defect–mediated transformation of a hafnium metal–organic framework
M J Cliffe, E Castillo-Martinez, Y Wu, J Lee, A C Forse, F C N Firth, P Z Moghadam, D Fairen-Jimenez, M W Gaultois, J A Hill, O V Magdysyuk, B Slater, A L Goodwin, and C P Grey
Journal of the American Chemical Society 139, 5397 (2017)

We report a hafnium containing MOF, hcp UiO-67(Hf), which is a defective layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its low- ered ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed ‘double cluster’, analogous to the condensation of coor- dination polyhedra in oxide frameworks. In oxide frameworks variable stoichiometry can lead to more complex defect structures, e.g. crystallographic shear planes or mod- ules with differing compositions, which can be the source of further chemical reactivity; likewise the layered hcp UiO-67 can react further to form two-dimensional nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions suggesting that defect ordered MOFs could be a productive route to porous two-dimensional materials.