Design and Precursor-based Solid-State Synthesis of Mixed-Linker Zr-MIL-140A

Acetic acid, an alternative green solvent, was utilized for the solvothermal synthesis of four 2D materials of composition [Zr₂O₂(OAc)₂(BDC-F)], [Zr₂O₂(OAc)₂(BDC-F₄)], [Zr₂O₂(OAc)₂(BDC)], and [Zr₂O₂(OAc)₂(NDC)] (BDC, terephthalate; BDC-F, 2-fluoroterephthalate; BDC-F₄, tetrafluoroterephthalate; NDC, 2,6-naphthalenedicarboxylate). The first three compounds were subsequently reacted with terephthalic acid in solid-state reactions to form porous MIL-140A-type metal-organic frameworks and mixed-linker derivatives ([ZrO(BDC)_1-(BDC-Y)], x = 0-0.18, Y = F, F₄). The reaction kinetics of the formation of MIL-140A were investigated with the aid of time-resolved synchrotron and temperature-resolved in-house X-ray powder diffraction experiments. Thorough compositional analyses and solid-state NMR spectroscopic experiments were used to assess the crystallographic ordering of the different linker molecules. Additionally, acetic acid-based routes for the direct synthesis of MIL-140A-NO₂ and a novel MIL-140A-(CH₃)₂ derivative were discovered.