Strongly Lewis acidic metal-organic frameworks for continuous flow catalysis

1. A method for preparing a catalyst, said method comprising:

(a) providing a parent metal-organic framework (MOF), wherein the parent MOF comprises periodic repeats of a coordination complex comprising (i) an organic bridging ligand, wherein the organic bridging ligand is trimesic acid (BTC) or 2,2′-bipyridine-5,5′-dicarboxylate (dcbpy); and (ii) a metal-containing secondary building unit (SBU), wherein said metal-containing SBU comprises a metal oxo cluster comprising a metal ion M and one or more terminal or bridging OH or OH 2 ligands, wherein the metal ion M is selected from a zirconium (Zr) ion, an iron (Fe) ion, a chromium (Cr) ion, and an aluminum (Al) ion; and

(b) reacting the parent MOF with a silyl triflate to replace one or more of the one or more terminal or bridging OH or OH 2 ligands with a triflate ligand.

2. The method of claim 1 , wherein the SBU is selected from the group consisting of a Zr-oxo cluster and an Al-oxo cluster.

3. The method of claim 1 , wherein the organic bridging ligand is trimesic acid (BTC).

4. The method of claim 1 , wherein the parent MOF is provided by contacting a parent precursor MOF with a strong acid, wherein the parent precursor MOF comprises periodic repeats of a coordination complex comprising: (i) the organic bridging ligand and (ii) a metal-containing SBU comprising a metal oxo cluster comprising the metal ion M and a monocarboxylate ligand; and wherein contacting the parent precursor MOF with the strong acid replaces the monocarboxylate ligand with an OH or OH 2 ligand.

5. The method of claim 1 , wherein the organic bridging ligand comprises a nitrogen-containing aryl or arylene group that can coordinatively bond to a metal ion, wherein said organic bridging ligand is dcbpy and the nitrogen-containing aryl or arylene group that can coordinatively bond to a metal ion is bipyridine.

6. The method of claim 5 , wherein the parent MOF is provided by contacting a parent precursor MOF with ozone, wherein the parent precursor MOF comprises coordination complexes between a metal-containing SBU comprising a metal oxo cluster, and at least two different organic bridging ligands, wherein one of the organic bridging ligands is dcbpy and the other organic bridging ligand is 1,4-benzenediacrylic acid; and wherein contacting the parent precursor MOF with the ozone replaces a coordinative bond between a 1,4-benzenediacrylic acid ligand and metal ion M of the SBUs with a coordinative bond between the metal ion M of the SBU and a hydroxide ligand.

7. The method of claim 5 , wherein the method further comprises contacting the MOF with a metal complex comprising a second metal ion M 2 , thereby metalating the nitrogen-containing aryl or arylene group of the organic bridging ligand with the second metal ion M 2 .

8. The method of claim 1 , wherein the catalyst is provided as a catalytic composite material and wherein providing the parent MOF comprises providing a parent composite material by:

(a1) contacting (i) BTC, (ii) a metal salt comprising the metal ion M, and (iii) silicon dioxide (SiO 2 ), alumina (Al 2 O 3 ), or titania (TiO 2 ) particles in a mixture of N,N-dimethylformamide and a monocarboxylic acid to form a parent precursor composite material, wherein the parent precursor composite material comprises particles of a parent precursor MOF attached to a surface of the SiO 2 , Al 2 O 3 , or TiO 2 particles, wherein said parent precursor MOF comprises periodic repeats of a coordination complex comprising BTC and metal-containing SBUs, wherein the metal-containing SBUs each comprise a metal oxo cluster comprising the metal ion M and further comprising a monocarboxylate ligand; and

(a2) reacting the parent precursor composite material with a strong acid to replace the monocarboxylate ligand with a hydroxide ligand, thereby forming the parent composite material comprising the parent MOF; and

wherein reacting the parent MOF with a silyl triflate comprises reacting the parent composite material with a silyl triflate, thereby replacing the hydroxide ligand with a triflate ligand.

9. The method of claim 1 , wherein the catalyst is provided as a catalytic composite material and wherein providing the parent MOF comprises providing a parent composite material by:

(a1) contacting dcbpy, 1,4-benzenediacrylic acid, and an aluminum salt in the presence silicon dioxide (SiO 2 ), alumina (Al 2 O 3 ), or titania (TiO 2 ) particles to form a parent precursor composite material, wherein the parent precursor composite material comprises particles of a parent precursor MOF attached to a surface of the SiO 2 , Al 2 O 3 , or TiO 2 particles, wherein said parent precursor MOF comprises coordination complexes between an Al-oxo cluster SBU and both the dcbpy and the 1,4-benzenediacrylic acid, and

(a2) reacting the parent precursor composite material with ozone to replace coordinative bonds between the 1,4-benzenediacrylic acid and Al ions of the SBU with coordinative bonds between the Al ions and a hydroxide ligand, thereby forming a parent composite material comprising the parent MOF; and

wherein reacting the parent MOF with a silyl triflate comprises reacting the parent composite material with (i) a silyl triflate, thereby replacing the hydroxide ligand with a triflate ligand; and (ii) a metal complex thereby metalating the bipyridine group of the dcbpy ligand.

10. A MOF catalyst prepared according to the method of claim 1 .