Metal-organic frameworks containing nitrogen-donor ligands for efficient catalytic organic transformations
Metal-organic framework (MOFs) compositions based on nitrogen donor-based organic bridging ligands, including ligands based on 1,3-diketimine (NacNac), bipyridines and salicylaldimine, were synthesized and then post-synthetically metalated with metal precursors, such as complexes of first row transition metals. Metal complexes of the organic bridging ligands could also be directly incorporated into the MOFs. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
1. A method for preparing a crystalline and porous metal-organic framework (MOF), wherein said crystalline and porous MOF comprises periodic repeats of a metal-based secondary building unit (SBU) and a nitrogen donor-based bridging ligand, said method comprising:
providing a nitrogen donor-based bridging ligand, wherein said nitrogen donor-based bridging ligand is a derivative of a 5,5′-bis(vinyl)-2,2′-bipyridine;
contacting the nitrogen donor-based bridging ligand with a first metal source to obtain the crystalline and porous MOF; and
contacting the crystalline and porous MOF with a second metal source to metalate the bridging ligand, wherein the second metal source comprises a metal selected from the group consisting of Fe, Co, Ni, Rh, Ru, Ir, Os, Pd, V, Cr, and Mn.
2. The method of claim 1 , wherein the 5,5′-bis(vinyl)-2,2′-bipyridine is substituted by two or more substituents selected from a carboxylate, pyridine, and/or phosphonate moiety.
3. The method of claim 2 , wherein the nitrogen donor-based bridging ligand is a 5,5′-bis(vinyl)-2,2′-bipyridine substituted with two carboxylate groups.
4. The method of claim 1 , wherein the nitrogen donor-based bridging ligand is 5,5′-bis(carboxyvinyl)-2,2′-bipyridine.
5. The method of claim 1 , wherein the SBU is selected from the group comprising Hf-oxo clusters, Zr-oxo clusters, Zn-oxo clusters, Ti-oxo clusters, Cu-carboxylate paddlewheels, and other SBUs used to construct MOFs.
6. The method of claim 1 , wherein the first metal source is a metal alkoxide or a metal halide.
7. The method of claim 1 , wherein the first metal source is ZrCl 4 .
8. The method of claim 1 , wherein the second metal source is FeCl 3 , CoCl 2 , NiCl 2 .
9. The method of claim 1 , wherein the MOF further comprises a bridging ligand that is not a nitrogen donor-based bridging ligand.
10. The method of claim 1 , wherein the nitrogen donor-based bridging ligand and the first metal source are contacted in a solvent or mixture of solvents selected based on solvent molecule size, such that the sizes and/or shapes of internal pores, cavities, and/or open channels in the crystalline and porous MOF can be tailored to enhance catalytic activity and selectivity.
11. A heterogeneous catalyst comprising a crystalline and porous MOF, wherein said crystalline and porous MOF comprises periodic repeats of a metal-based secondary building unit (SBU), wherein said metal-based SBU comprises a first metal, and a nitrogen donor-based bridging ligand, wherein said nitrogen donor-based bridging ligand is a derivative of a 5,5′-bis(vinyl)-2,2′-bipyridine; and wherein said nitrogen donor-based bridging ligand is further complexed to a second metal, wherein the second metal is selected from the group consisting of Fe, Co, Ni, Rh, Ru, Ir, Os, Pd, V, Cr, and Mn.
12. A heterogeneous catalyst prepared according to the method of claim 1 .
13. A method for preparing a compound comprising contacting a substrate capable of forming a product by catalytic transformation with a heterogeneous catalyst of claim 11 .
14. The method of claim 13 , wherein the catalytic transformation is selected from the group comprising hydrogenation; dehydrogenation; isomerization, optionally the isomerization of an allylamine, an allyl alcohol, or an α,β-unsaturated ketone; allylic substitution; a coupling reaction, optionally wherein the coupling reaction is a Buchwald-Hartwig amination, an intramolecular Heck reaction, or an intermolecular Heck reaction; conjugate addition, optionally wherein the conjugate addition is a Michael addition or an azo-Michael addition; an aldol reaction; a Mannich-type reaction; nucleophilic addition, optionally wherein the nucleophilic addition is to a carbonyl or imine group and/or wherein the nucleophilic addition is a cyanation, a propargylation, an allylation, a dienylation, an arylation, an alkenylation, or an alkylation; hydroformylation; hydroacylation; hydroboration; hydroamination; intra- or intermolecular hydrosilylation; an α-substitution reaction, optionally wherein the α-substitution reaction is a protonation, a fluorination, an amination, an arylation, or an orthoester alkylation; an ene reaction; a Diels-Alder reaction; a Pauson-Khand reaction; an enyne intramolecular cyclization; a [2+2+2] cycloaddition; a [3+2] cycloaddition; and a ring-opening reaction.
15. The heterogeneous catalyst of claim 11 , wherein the MOF further comprises a bridging ligand that is not a nitrogen donor-based bridging ligand.