The metal sites of MIL-100(Fe), MIL-100(Fe,Al), and MIL-100(Al) metal−organic frameworks (MOFs) were decorated with ethylenediamine (EN). Interestingly, the Alcontaining MOFs presented hierarchized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule in each trimeric Al 3 O cluster unit, whereas the other two aluminum sites are occupied by a hydroxyl and a water molecule. The −NH 2 sites of the grafted ethylenediamine can be used for further postfunctionalization through amine chemistry and are responsible for the basicity of the functionalized material as well as increased affinity for CO 2 . Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity. Finally, the Al-containing MOFs show an unusual carbon dioxide sorption mechanism at high pressures that distinguishes those materials from their iron and chromium counterparts and is suspected to be due to the presence of polarized Al−OH bonds.

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 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 PXRD measurements demonstrated that this highly air-sensitive TiIII-containing MOF is structurally stable up to 200°C. Nuclear magnetic resonance (NMR) spectroscopy, elemental and inductively-coupled plasma (ICP) analyses 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 reveal a higher affinity of this MOF for hydrogen compared to the previously described monometallic unfunctionalized MIL-101(TiIII) MOF.

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–x Al x Cl3(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.

The metal sites of MIL-100(Fe), MIL-100(Fe,Al) and MIL-100(Al) MOFs were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierachized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule by trimeric Al3O cluster unit, whereas the two other aluminium sites are occupied by an hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further post-functionalization through amine chemistry and is responsible for basicity of the functionalized material. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity and for a unique carbon dioxyde sorption mecanism, that distinguishes this material from its iron and chromium couterparts.

The metal sites of MIL-100(Fe), MIL-100(Fe,Al) and MIL-100(Al) MOFs were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierachized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule by trimeric Al3O cluster unit, whereas the two other aluminium sites are occupied by an hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further post-functionalization through amine chemistry and is responsible for basicity of the functionalized material. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity and for a unique carbon dioxide sorption mecanism, that distinguishes this material from its iron and chromium counterparts.