Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
Department of Materials Science & Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
J Am Chem Soc. 2017 Apr 19;139(15):5397-5404. doi: 10.1021/jacs.7b00106. Epub 2017 Apr 5.
We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed "double cluster" (HfO(OH)), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal-organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal-organic 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.
我们报告了一种含铪的金属有机骨架材料 hcp UiO-67(Hf)，它是面心立方 fcu UiO-67(Hf)的配体缺陷层状类似物。与 fcu UiO-67 相比，hcp UiO-67 通过一种新的结构机制来容纳其较低的配体与金属比：形成凝聚的“双簇”（HfO(OH)），类似于氧化骨架中配位多面体的凝聚。在氧化物骨架中，可变的化学计量比可能导致更复杂的缺陷结构，例如，晶体剪切平面或具有不同组成的模块，这些可能是进一步化学反应性的来源；同样，层状 hcp UiO-67 可以进一步反应以可逆地形成二维金属有机骨架 hxl UiO-67。三维 hcp UiO-67 和二维 hxl UiO-67 都可以剥离形成金属有机纳米片。hcp UiO-67 的剥离是通过强铪-羧酸盐键的断裂实现的，并且在温和的条件下进行，这表明缺陷有序的 MOF 可能是制备多孔二维材料的有效途径。
