Enhancing catalytic performance via structure core-shell metal-organic frameworks

A core-shell structure metal-organic framework based on the Zr clusters bridging with BDC linkers (UiO-66) as a core-structure and BPYDC linkers (UiO-67-BPY) as a shell-structure was developed (UiO-67-BPY@UiO-66). The combination of several techniques such as XRD, FTIR, SEM, TEM, and surface area analysis etc. were applied for the characterization and confirmed a core-shell structure of UiO-67-BPY@UiO-66. Taking advantage of the high porous stability of the core-structure (UiO-66) and the presence of active Lewis basic sites from the bipyridinic linker in the shell layer (UiO-67-BPY) could be advantageous for basic-catalyzed reactions. The synthesized core-shell material was applied as a heterogeneous catalyst for the Knoevenagel condensation as a model reaction. An excellent catalytic performance was obtained by the core-shell material over traditional MOFs and other previous reports based on MOFs. The excellent dispersion of the active sites (Lewis basic) in the outer layer of the designed core-shell structure was a breakthrough to prevent mass diffusion limitation during catalysis. Additionally, the catalyst can be recycled and maintained its high catalytic performance at least for four cycles.