title: Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds.
abstract: Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam)(2x)(Lcam)(2-2x)(dabco)]n (dabco = 1,4-diazabicyclo-[2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)]n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu2(Dcam)2(dabco)]n and [Cu2(Lcam)2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture.
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe (Germany).
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Gu
authors.forename: Jochen
authors.initials: J
authors.lastname: Bürck
authors.forename: Angela
authors.initials: A
authors.lastname: Bihlmeier
authors.forename: Jinxuan
authors.initials: J
authors.lastname: Liu
authors.forename: Osama
authors.initials: O
authors.lastname: Shekhah
authors.forename: Peter G
authors.initials: PG
authors.lastname: Weidler
authors.forename: Carlos
authors.initials: C
authors.lastname: Azucena
authors.forename: Zhengbang
authors.initials: Z
authors.lastname: Wang
authors.forename: Stefan
authors.initials: S
authors.lastname: Heissler
authors.forename: Hartmut
authors.initials: H
authors.lastname: Gliemann
authors.forename: Wim
authors.initials: W
authors.lastname: Klopper
authors.forename: Anne S
authors.initials: AS
authors.lastname: Ulrich
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
mesh_terms: D002942:Circular Dichroism; D003460:Crystallization; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D009942:Organometallic Compounds
keywords: chirality; computational chemistry; enantioselectivity; oriented circular dichroism; surface-anchored metal-organic framework