Yolk-Shell and Hollow Zr/Ce-UiO-66 for Manipulating Selectivity in Tandem Reactions and Photoreactions

One of the hallmarks of multicomponent metal-organicframeworks(MOFs) is to finely tune their active centers to achieve product selectivity.In particular, obtaining bimetallic MOF hollow structures with preciselytailored redox centers under the same topology is still challengingdespite a recent surge of such efforts. Herein, we present an engineeringstrategy named "cluster labilization" to generate hierarchicallyporous MOF composites with hollow structures and tunable active centers.By partially replacing zirconium with cerium in the hexanuclear clustersof UiO-66, unevenly distributed yolk-shell structures (YSS)were formed. Through acid treatment or annealing of the YSS precursor,single-shell hollow structures (SSHS) or double-shell hollow structures(DSHS) can be obtained, respectively. The active centers in SSHS andDSHS differ in their species, valence, and spatial locations. Moreimportantly, YSS, SSHS, and DSHS with distinct active centers andmicroenvironments exhibit tunable catalytic activity, reversed selectivity,and high stability in the tandem reaction and the photoreaction.