Chiral Metal-Organic Frameworks

In the past two decades, metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) assembled from metal ions or clusters and organic linkers via metal-ligand coordination bonds have captivated significant scientific interest on account of their high crystallinity, exceptional porosity, and tunable pore size, high modularity, and diverse functionality. The opportunity to achieve functional porous materials by design with promising properties, unattainable for solid-state materials in general, distinguishes MOFs from other classes of materials, in particular, traditional porous materials such as activated carbon, silica, and zeolites, thereby leading to complementary properties. Scientists have conducted intense research in the production of chiral MOF (CMOF) materials for specific applications including but not limited to chiral recognition, separation, and catalysis since the discovery of the first functional CMOF (i.e., d- or l-POST-1). At present, CMOFs have become interdisciplinary between chirality chemistry, coordination chemistry, and material chemistry, which involve in many subjects including chemistry, physics, optics, medicine, pharmacology, biology, crystal engineering, environmental science, etc. In this review, we will systematically summarize the recent progress of CMOFs regarding design strategies, synthetic approaches, and cutting-edge applications. In particular, we will highlight the successful implementation of CMOFs in asymmetric catalysis, enantioselective separation, enantioselective recognition, and sensing. We envision that this review will provide readers a good understanding of CMOF chemistry and, more importantly, facilitate research endeavors for the rational design of multifunctional CMOFs and their industrial implementation.

An effective strategy for creating asymmetric MOFs for chirality induction: a chiral Zr-based MOF for enantioselective epoxidation

A simple and rapid procedure was used to prepare chiral NU-1000 as a robust Zr-based MOF without complexity. The functionalization of NU-1000 was performed by utilizing chirall-(+)-tartaric acidviasolvent-assisted linker incorporation, resulting in [C-NU-1000]. A Mo-complex was immobilized onto chiral NU-1000 for enantioselective epoxidation.

Unprecedented homochiral 3D lanthanide coordination polymers with triple-stranded helical architecture constructed from a rigid achiral aryldicarboxylate ligand

Luminescence and second harmonic generation activity of a series of homochiral 3D Ln-CPs were studied.

Flexible and rigid dicarboxylic acids enable the assembly of achiral and chiral 3D Co(ii) metal–organic frameworks

The homochirality of the 3D Co(ii) MOFs may arise from the rotation of the two phenyl rings in the biphenyl-4,4′-dicarboxylic acid ligand.

Chiral metal–organic frameworks constructed from four-fold helical chain SBUs for enantioselective recognition of α-hydroxy/amino acids

Three chiral 3D metal–carboxylate frameworks have been successfully synthesized, featuring four-fold helical metal chains as SBUs. Co-MOFs could recognize enantio-selectively α-hydroxy/amino acids by the change of CD signals.

A second-order nonlinear optical material with a 5-fold interpenetrating diamondoid framework based on two achiral precursors: spontaneous resolution to absolute chiral induction

A pair of enantiomeric Zn(ii) complexes have been synthesized through spontaneous resolution. Fortunately, the handedness of bulk crystals can be controlled by using a chiral induction agent. Notably, they display strong SHG response.

Control of bulk homochirality and proton conductivity in isostructural chiral metal–organic frameworks

Two enantiomeric pairs of isostructural homochiral metal–organic frameworks (MOFs) have been synthesized directly from chiral ligands and indirectly from achiral ligandsviaspontaneous resolution combined with cooperative chirality induction, respectively.

Enantiopure anion templated synthesis of a zeolitic metal-organic framework

Utilizing (R)-H3CIA as a chiral template, an unprecedented homochiral metal-organic framework (MOF) with zeotype GIS topology is obtained from achiral 1.4-DIB ligands and Zn(II) ions, which opens up a feasible approach to create zeolitic MOFs with homochirality.

Homochiral and heterochiral Mn(II) coordination frameworks: spontaneous resolution dependent on dipyridyl ligands

An unsymmetric tetracarboxylic ligand collaborates with 4,4'-bipyridine to induce spontaneous resolution to form homochiral 3D coordination frameworks, while the use of longer dipyridyl ligands instead of 4,4'-bipyridine leads to isoreticular but heterochiral frameworks.

Hexagonal Co6 and zigzag Co4 cluster based magnetic MOFs with a pcu net for selective catalysis

Two magnetic MOFs with a pcu net, constructed by using hexagonal Co₆ rings and zigzag Co₄ clusters, respectively are reported. Furthermore, activated 1 exhibits an excellent catalytic selectivity in the allylic oxidation reaction of cyclohexene to form an α,β-unsaturated ketone.

Enantiopure phosphonic acids as chiral inducers: homochiral crystallization of cobalt coordination polymers showing field-induced slow magnetization relaxation

Homochiral crystallization of (M)- or (P)-Co(SO₄)(1,3-bbix)(H₂O)₃ (1M or 1P) from an achiral precursor is achieved in the presence of a catalytic amount of (S)- or (R)-3-phenyl-2-((phosphonomethyl)amino) propanoic acid.

Rare double spin canting antiferromagnetic behaviours in a [Co24] cluster

A fish-basket-shaped [Co₂₄] cluster, [Co₂₄(μ₃-O)₄(ampc)₄(μ₃-OH)₄(μ₂-OH)₄(NO₃)₅(HCO₂)₂₂(H₂O)₁₀]·[(HCO₂)·2(CH₃OH)·x(H₂O)], was woven by bridging oxygen atoms from O²⁻, OH⁻, NO₃⁻ and HCO₂⁻ groups, and stabilized terminally by a semi-rigid organic ligand 4′,4′-[(dimethylamino)dimethylene]-bis[(1,1′-biphenyl)-2-carboxylate] (ampc⁻).

Spontaneous symmetry breaking of Co(ii) metal–organic frameworks from achiral precursors via asymmetrical crystallization

Enantioenriched 3D pseudo-enantiomorphs integrating porosity, chirality and magnetism together with different colour and morphology were obtained through spontaneous symmetry breaking.

Spontaneous chiral resolution of a rare 3D self-penetration coordination polymer for sensitive aqueous-phase detection of picric acid

A chiral, fluorescent and self-penetration coordination polymer was synthesized through spontaneous resolution, which showed sensitive detection of picric acid in the aqueous phase.