In Situ Imine-Based Linker Formation for the Synthesis of Zirconium MOFs: A Route to CO2 Capture Materials and Ethylene Oligomerization Catalysts

In situ formation of imine-based organic linkers facilitates the formation of metal-organic frameworks (MOFs), in particular if linker solubility hampers the direct synthesis. The reaction of ZrCl4 with 4-formylbenzoic acid or 4-formyl-3-hydroxybenzoic acid as the aldehyde source and 4-aminobenzoic acid as the amine source is shown to produce zirconium MOFs isoreticular to UiO-66 (PCN-161 and a novel DUT-133, [Zr6O4 (OH)(4) (C15H9NO5)(6)], respectively). A similar reaction with p-phenylenediamine as the amine-containing building block gave 2-fold interpenetrated framework (PCN-164). Detailed characterization, including single crystal and powder X-ray diffraction, water stability tests, thermal stability, and in situ H-1 and C-13 NMR were performed to elucidate the formation mechanism of zirconium MOFs containing imine-based linkers. The resulting zirconium MOFs were evaluated as potential materials for CO2 capture and as ethylene oligomerization catalysts with anchored nickel as the active species.