Metal organic framework
a technology of organic framework and metal, applied in the direction of organic compound/hydride/coordination complex catalyst, physical/chemical process catalyst, hydrocarbon preparation catalyst, etc., can solve the problems of diverse set of challenges, low activity and rapid deactivation,
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example 1
[0101]Ionic Liquids in MOFs
[0102]For MOF-supported Ionic Liquids (ILs), the anchor point could be the metal node or a functional group on the linker. ILs are salts with a low melting point, typically less than 100° C. The origin of the low melting point is the charge delocalization in its bulky constituent ions, leading to small lattice enthalpies and large entropy changes that favor melting. The variety of choices for cations and anions provides a high synthetic flexibility for ILs, and this flexibility is magnified by the ability to make IL mixtures.
[0103]ILs can display Lewis or Brønsted acidity or both. Most of the known Lewis acidity comes from the electron-pair-accepting ability of the anion, while Brønsted acidity can come from the cation and / or the anion. Additional Brønsted sites such as —SO3H can also be introduced through alkyl side chains tethered to the ionic core.
[0104]For alkylation, ILs containing multinuclear halometallate anions such as [Al2Cl7]− are highly active ...
example 2
[0105]MOF-Supported Heteropolyacids
[0106]Heteropolyacids (HPAs), specifically phosphotungstic acid (PTA), had been encapsulated in MOF pores. MOFs used to host H3PW12O40 include MIL-100, MIL-101, UiO-67, NU-1000, HKUST-1, ZIF-67 and ZIF-8. HPAs are solid acids that incorporate transition metal-oxygen clusters as anions. They are called the Keggin and Wells-Dawson structures, and like other HPA anions, they feature metal-oxygen octahedral as a basic structural unit. The most common metals that make up the octahedral are tungsten, molybdenum, and vanadium. The anion is formed when these octahedral surround one or more heteroatoms, which are often phosphorous or silicon. The acidity of HPAs is purely Brønsted in nature. For the commercially available Keggin-type HPAs, the acid strength decreases in the order H3PW12O40>H4SiW12O40>H3PMo12O40>H4SiMo12O40. H3PW12O40 (called phosphotungstic acid, hereon referred to as PTA) was found to be more acidic than H2SO4 and is therefore a suitable a...
example 3
[0132]Sulfonic Acid-Functionalized MOFs
[0133]Catalysts bearing perfluorinated sulfonic acid groups have high acid strength. A well-known example is Nafion, which had been reported in literature as an alkylation catalyst. In this invention, solid acid catalysts comprised of MOFs bearing halogenated and non-halogenated alkyl- and arylsulfonic acid sites are targeted.
[0134]The solid acid catalysts disclosed in this example are MOFs functionalized with halogenated and non-halogenated alkyl and aryl sulfonic acids. The functionalized MOF is prepared by a reaction between the nucleophilic groups present in the MOF's building units and cyclic sulfonate esters called sultones. Such reaction can yield sulfonic acids in the MOF's internal surface. These MOFs may be used as acid catalysts, even for those reactions that require high acid strength such as isoparaffin-olefin alkylations. Using perflourinated sultones can yield perfluorosulfonic acid sites on the MOFs, reminiscent of the highly ac...
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