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

Abstract

<i>In situ</i> 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 <i>p</i>-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 <i>in situ</i> ¹H and ¹³C 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.