Fig. 3: Defect type and spatial distribution in UiO-66.

The MOF UiO-66 is composed of BDC linkers interconnected by 12 connected M^IV-oxo clusters (M = Zr, Hf) to form a robust and highly porous network. A representation of the ideal structure with fcu net, including the ideal 12-connected cluster, is presented (a). The material is highly susceptible to defects including ML (bcu net) and MC (reo or scu net) (b). MC defects are known to form correlated defect nanoregions in some UiO samples, leading to aggregation of defects which is represented schematically in i) and ii). HRTEM image showing significant correlation of missing cluster defects adopting the scu net (scale bar represents 5 nm) iii. The scu structural model, simulated potential map and actual averaged HRTEM image representing one unit cell (left to right, iv). Image components c(ii) adapted with permission from ref. ²¹. Copyright 2014 Springer Nature and c(iii)-c(iv) adapted with permission from ref. ¹⁹. Copyright 2019 Springer Nature.