Synthesis, Structure, and Thermal Stability of a Mesoporous Titanium(III) Amine-Containing MOF

Abstract

The first mesoporous bimetallic TiIII/Al metal–organic framework (MOF) containing amine functionalities on its linkers has been selectively obtained by converting the cheap commercially available (TiCl3)3AlCl3 into Ti3–xAlxCl3(THF)3 and reacting this complex with 2-aminoterephthalic acid in dimethylformamide (DMF) under soft solvothermal conditions. This compound is structurally related to the previously described NH2-MIL-101(M) (M = Cr, Al, and Fe) MOFs. Thermal gravimetric analyses and in situ powder X-ray diffraction (PXRD) measurements demonstrated that this highly air-sensitive TiIII-containing MOF is structurally stable up to 200 °C. Nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and inductively coupled plasma (ICP) revealed that NH2-MIL-101(TiIII) contains trinuclear Ti3(μ3-O)Cl(DMF)2(RCOO)6 clusters with strongly bound DMF molecules and a small amount of aluminum. Sorption experiments revealed a higher affinity of this MOF for hydrogen compared to the previously described monometallic unfunctionalized MIL-101(TiIII) MOF.