A Homochiral Metal–Organic Material with Permanent Porosity, Enantioselective Sorption Properties, and Catalytic Activity

Abstract

Metal-organic porous materials are receiving growing attention [1] because of their potential applications in gas storage, [2] separation, [3] and many other areas. [4] Although catalysis is one of the most promising applications of such materials, only a handful of examples have been reported to date. [5] Furthermore, despite considerable efforts, attempts to synthesize robust, homochiral metal-organic porous materials capable of enantioselective separation and/or catalysis have met with only limited success. [6,7] Most homochiral metalorganic frameworks are not robust enough to show permanent porosity, nor porous enough to be useful for selective sorption or catalytic transformation of organic molecules. Therefore, the synthesis of robust homochiral metal-organic frameworks with potential for application is still challenging. For the synthesis of homochiral metal-organic open frameworks, two general approaches have been taken: 1) use of a rigid homochiral organic ligand as a spacer to link adjacent metal centers or secondary building units (SBUs), [5b-d, 7] and 2) use of a homochiral ligand as an auxiliary pendant which does not directly participate in the formation of a framework backbone, but forces the framework to adopt a specific chiral topology.[3d] Herein, we introduce another rational approach to the synthesis of homochiral metal-organic frameworks. A metal ion and a readily available homochiral organic ligand are used to form homochiral SBUs, which in turn, are linked together by rigid spacers to build a network structure, in a one-pot reaction (Scheme 1).[8] With a judicious choice of metal ion, homochiral organic molecule, and rigid polytopic linker (that is, a connector with more than one metal coordination site), this approach allows us to synthesize metal-organic open frameworks with stable chiral pores. Herein, we report a new homochiral metal-organic material that has permanent porosity, size-and enantioselective sorption properties, and catalytic activity.[9]

Metal-Organic Frameworks as Selective or Chiral Oxidation Catalysts

“…A similar approach has been employed by the same group using another Tibased salan complex (Scheme 13d) to form a salan complex based MOF structure, the obtained MOF catalyst also shows good selectivity (up to 62% ee) in the oxidation of sulfides to sulfoxides (Table 5, entry 12). 128 Whereas the previous studies report on the application of chiral MOFs in the epoxidation of alkenes, Dybtsev et al examined a homochiral Zn MOF in the size-and chemoselective oxidation of thioethers (entry 5, Table 5) 129 . The chiral MOF exhibited a reasonable conversion (58-64%) for the smaller thioethers whereas for the bulkier thioethers a very poor conversion was noted.…”

Crystal structure of poly[diaqua-μ5-4-(3,5-dicarboxylato-κ 3 O 1:O 2:O 3-phenoxy)phthalato-κ 3 O 5,O 7:O 8)(μ2-4-(1H-pyrazol-5-yl)pyridine-κ

“…The keen interest in the design and synthesis of coordination polymers (CPs) stems not only because of their potential applications in gas storage, molecular sieves, catalysis, drug delivery, nonlinear optics, and molecular sensing, but also because of impressive structural topologies [1][2][3]. Over the past decades, numerous CPs have been successfully constructed, and crystal engineering has reached a relatively mature level that some CPs with speci c topologies can be designed by the judicious selection of metal ions and organic ligands [4].…”

A Tale of Three Carboxylates: Cooperative Asymmetric Crystallization of a Three‐Dimensional Microporous Framework from Achiral Precursors

“…With few exceptions, homochiral porous solids prepared so far acquire homochirality through the incorporation of enantiopure organic ligands that are bonded to the crystalline framework either as a crosslinking ligand or pendant ligand. [1][2][3][7][8][9] In the absence of enantiopure building blocks, the chirality can be generated from achiral precursors through crystallization, as evidenced by many crystals (such as quartz) reported in enantiomorphous space groups. [4] In these crystals, chirality comes from the spatial organization of achiral building blocks.…”