Search

In this article, chiral covalent organic framework core‐shell composite CCOF‐TpPa‐Py@SiO2 was facilely synthesized by induction at room temperature. The CCOF‐TpPa‐Py@SiO2 core‐shell composite was used as a chiral stationary phase for the separation of the racemates by high‐performance liquid chromatography, which exhibits good separation performance for chiral compounds including ketones, alcohols, esters, epoxides, carboxylic acids, amides, and amines. The effects of analyte injection mass on the enantioseparation were studied. The reproducibility and stability of the CCOF‐TpPa‐Py@SiO2 chiral column were explored. The intra‐day (n = 5), inter‐day (n = 5), and inter‐column (n = 3) relative standard deviations for the migration times and resolution of benzoin were 0.32%–0.54%, 0.45%–0.61%, and 1.21%–1.53%, respectively. In addition, the chiral separation ability of the CCOF‐TpPa‐Py@SiO2 chiral column (column A) was compared with that of the MDI‐β‐CD‐Modified COF@SiO2 (column B) as well as a commercial chiral column (Chiralpak AD‐H). The chiral recognition ability of column A is complementary to that of column B and AD‐H column. The resolution mechanism of CCOF‐TpPa‐Py@SiO2 stationary phase towards chiral analyte was explored. Hence, the synthesis of CCOF‐TpPa‐Py@SiO2 core‐shell composite by induction at room temperature as chiral stationary phases for chromatographic separation has important research potential and application prospects. [ABSTRACT FROM AUTHOR]

A chiral pillar[3]trianglimine (C60H72N6O6) with a deep cavity has been developed as a chiral selector and bonded to thiolated silica by thiol‐ene click reaction to fabricate a novel chiral stationary phase for enantioseparation in high‐performance liquid chromatography. The enantioseparation performance of the fabricated chiral stationary phase has been evaluated by separating various racemic compounds, including alcohols, esters, amines, ketones, amino acids, and epoxides, in both normal‐phase and reversed‐phase elution modes. In total, 14 and 17 racemates have been effectively separated in these two separation modes, respectively. In comparison with two widely used chiral columns (Chiralcel OD‐H and Chiralpak AD‐H), our novel chiral stationary phase offered good chiral separation complementarity, separating some of the tested racemates that could not be separated or were only partially separated on these two commercial columns. The influences of analyte mass, mobile phase composition, and column temperature on chiral separation have been investigated. Good repeatability, stability, and column‐to‐column reproducibility of the chiral stationary phase for enantioseparation have been observed. After the fabricated column had been eluted up to 400 times, the relative standard deviations (n = 5) of resolution (Rs) and retention time of the separated analytes were < 0.39% and < 0.20%, respectively. The relative standard deviations (n = 3) of Rs and retention time for column‐to‐column reproducibility were < 4.6% and < 5.2%, respectively. This study demonstrated that the new chiral stationary phase has great prospects for chiral separation in high‐performance liquid chromatography. [ABSTRACT FROM AUTHOR]

Porous organic cages (POCs) are a new subclass of porous materials, which are constructed from discrete cage molecules with permanent cavities via weak intermolecular forces. In this study, a novel chiral stationary phase (CSP) has been prepared by chemically binding a [4 + 6]-type chiral POC (C120H96N12O4) with thiol-functionalized silica gel using a thiol-ene click reaction and applied to HPLC separations. The column packed with this CSP presented good separation capability for chiral compounds and positional isomers. Thirteen racemates have been enantioseparated on this column, including alcohols, diols, ketones, amines, epoxides, and organic acids. Upon comparison with a previously reported chiral POC NC1-R-based column, commercial Chiralpak AD-H, and Chiralcel OD-H columns, this column is complementary to these three columns in terms of its enantiomeric separation; and can also separate some racemic compounds that cannot be separated by the three columns. In addition, eight positional isomers (iodoaniline, bromoaniline, chloroaniline, dibromobenzene, dichlorobenzene, toluidine, nitrobromobenzene, and nitroaniline) have also been separated. The influences of the injection weight and column temperature on separation have been explored. After the column has undergone multiple injections, the relative standard deviations (RSDs) for the retention time and selectivity were below 1.0 and 1.5%, respectively, indicating the good reproducibility and stability of the column for separation. This work demonstrates that POCs are promising materials for HPLC separation. [ABSTRACT FROM AUTHOR]

Chiral metal‐organic frameworks have shown great potential in enantioselective separation and asymmetric catalysis due to their diverse and adjustable structures with abundant chiral recognition sites. Herein, a new chiral post‐synthetic modification was used for preparing an achiral@chiral metal‐organic frameworks core‐shell composite [Cu3(Btc)2]@[Cu2((+)‐Cam)2Dabco] by a superficial chiral etching method. The [Cu3(Btc)2]@[Cu2((+)‐Cam)2Dabco] composite was utilized as a novel chiral stationary phase for HPLC enantioseparation. Various racemates were separated on the [Cu3(Btc)2]@[Cu2((+)‐Cam)2Dabco]‐packed column (column A). It exhibited good chiral resolving ability toward many different kinds of racemates, especially chiral drugs. Among them, the highest resolution value for 1,2‐diphenyl‐1,2‐ethanediol reaches 2.70. The relative standard deviations of retention time and peak area for repeated separation of 1,2‐diphenyl‐1,2‐ethanol were 0.45% and 0.81%, respectively. Compared with the resolution ability of [Cu2((+)‐Cam)2Dabco]‐packed column (column B), column A shows higher column efficiency and better separation performance than those of column B. The results indicated that the [Cu3(Btc)2]@[Cu2((+)‐Cam)2Dabco] as a stationary phase can greatly improve the column efficiency and chiral resolution ability of chiral metal‐organic frameworks, which demonstrated that the superficial chiral etching as an economic and efficient strategy opens up a new way for the application of metal‐organic frameworks. [ABSTRACT FROM AUTHOR]

A spherical chiral porous organic polymer (POPs) COP-1 is synthesized by the Friedel–Crafts alkylation reaction of Boc-3-(4-biphenyl)-L-alanine (BBLA) and 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCMBP), which was used as a novel chiral stationary phase (CSPs) for mixed-mode high-performance liquid chromatography (HPLC) enantioseparation. The racemic compounds were resolved in normal-phase liquid chromatography (NPLC) using n-hexane/isopropanol as mobile phase and reversed-phase liquid chromatography (RPLC) using methanol/water as mobile phase. The COP-1-packed column exhibited excellent separation performance toward various racemic compounds including alcohols, amines, ketones, esters, epoxy compounds, organic acids, and amino acids in NPLC and RPLC modes. The effects of analyte mass and column temperature on the separation efficiency of racemic compounds were investigated. In addition, the chiral resolution ability of the COP-1-packed column not only can be complementary in RPLC/NPLC modes but also exhibit a good chiral recognition complementarity with Chiralpak AD-H column and chiral porous organic cage (POC) NC1-R column. The relative standard deviations (RSD) (n = 5) of the retention time, resolution value, and peak area by repeated separation of 1-(4-chiorophenyl)ethanol are all below 3.0%. The COP-1 column shows high column efficiency (e.g., 17,320 plates m−1 for 1-(4-chlorophenyl)ethanol on COP-1 column in NPLC), high enantioselectivity, and good reproducibility toward various racemates. This work demonstrates that chiral POPs microspheres are promising chiral materials for HPLC enantioseparation. [ABSTRACT FROM AUTHOR]

Separations and analyses of chiral compounds are important in many fields, including pharmaceutical production, preparation of chemical intermediates, and biochemistry. High‐performance liquid chromatography using a chiral stationary phase is regarded as one of the most valuable methods for enantiomeric separation and analysis because it is highly efficient, is broadly applicable, and has powerful separation capability. The focus for development of this method is the identification of novel chiral stationary phases with superior recognition performance and good stability. The present article reviews recent progress in the development of new chiral stationary phases for high‐performance liquid chromatography between January 2018 and June 2021. These newly reported chiral stationary phases are divided into three categories: small organic molecule‐based (cyclodextrin and its derivatives, macrocyclic antibiotics, cinchona alkaloids, and other low molecular weight chiral molecules), macromolecule‐based (cellulose and amylose derivatives, chitin and chitosan derivatives, and synthetic helical polymers) and chiral porous material‐based (chiral metal‐organic frameworks, chiral covalent organic frameworks, and chiral inorganic mesoporous silicas). Each type of chiral stationary phase is discussed in detail. [ABSTRACT FROM AUTHOR]

The unique features of uniform and adjustable cavities, abundant chiral active sites, and high enantioselectivity make chiral metal‐organic frameworks popular as an emerging candidate for enantioselective separation. However, the wide particle size distribution and irregular shape of as‐synthesized metal–organic frameworks result in low column efficiency, undesired chromatographic peak shape, and high column backpressure of such metal–organic frameworks packed columns. Herein, we report the fabrication of chiral core‐shell microspheres [Cu2(d‐Cam)2(4,4′‐bpy)]n@SiO2 composite for high‐performance liquid chromatography enantioseparation to overcome the above‐mentioned problems. The [Cu2(d‐Cam)2(4,4′‐bpy)]n@SiO2 packed column gave high‐resolution separation of racemates under low column backpressure (10‐22 bar), indicating its synergistic effect of the good column packing property of the SiO2 microspheres and the chiral recognition ability of [Cu2(d‐Cam)2(4,4′‐bpy)]n crystals. Thirteen kinds of chiral compounds including alcohols, amines, ketones, epoxides, and organic bases were well separated with good peak shapes and high column efficiency (18200 plates/m for 1‐(9‐anthryl)‐2,2,2‐trifluoroethanol) on the [Cu2(d‐Cam)2(4,4′‐bpy)]n@SiO2 packed column. Among them, seven pairs of enantiomers achieved baseline separation and the resolution value for 1‐(9‐anthryl)‐2,2,2‐trifluoroethanol reached 11.22. Some effects such as column temperature, and analytes mass on the enantioseparations have been investigated. In addition, the [Cu2(d‐Cam)2(4,4′‐bpy)]n@SiO2 packed column exhibited good stability and repeatability for the separation of chiral compounds. The relative standard deviations for five replicate separations of 1‐phenylethanol were less than 1.0, 1.5, 3.0, and 2.0% for the retention time, peak area, number of theoretical plates, and resolution, respectively. The research results demonstrated the development of chiral metal–organic frameworks core‐shell microspheres composite provide a promising platform for their practical application in chiral separation fields. [ABSTRACT FROM AUTHOR]

A hydroxyl-functionalized homochiral porous organic cage (POC) was synthesized and characterized by FTIR, NMR, thermogravimetric analysis (TGA), MALDI-TOF-MS, and elemental analysis. The synthesized homochiral POC was used as stationary phase to prepare a capillary gas chromatography (GC) column by a static coating method. The fabricated column shows excellent selectivity not only for the separation of positional isomers but also for the resolution of various racemates. Thirty-nine racemates have been resolved on the column, including alcohols, diols, halohydrocarbons, epoxides, esters, lactones, ketones, ethers, and organic acids. Compared to the commercial β-DEX 120 column and previously reported chiral POCs (CC3-R, CC9, and CC10)-coated columns, there are 11, 10, 24, and 15 tested racemates that cannot be resolved on β-DEX 120 column, CC3-R column, CC9 column, and CC10 column, respectively. This reveals that the fabricated column has prominent complementarity or superior separation performance to these columns in enantioseparation. Besides, the fabricated column can achieve some enantioseparations which are not possible using all previously reported chiral POC-based columns. Some positional isomers (xylenes, dichlorobenzenes, dibromobenzenes, nitrochlorobenzenes, and nitrobromobenzenes) were also separated with high-resolution values. The column exhibits good repeatability, reproducibility, and stability. The relative standard deviation (RSD) values of retention times were 0.03–0.18%, 0.11–0.92%, and 2.1–6.6% for run-to-run (n = 5), day-to-day (n = 5), and column-to-column (n = 3), respectively. The experimental results demonstrate the great potential of POCs for practical application in GC. [ABSTRACT FROM AUTHOR]

Mesoporous materials are promising functional materials due to their properties, such as a large surface area, tunable pore size, structure and morphology. Chiral mesoporous silica is an indispensable part of mesoporous materials. Considering that chirality is rare in inorganic mesoporous materials, there are very few reports on chiral inorganic mesoporous silica for chromatographic separations. In this work, we report the use of chiral inorganic mesoporous silica based on the template of myristyl chloride‐l‐valine sodium as the stationary phase for enantioselective separation in gas chromatography. Thirteen chiral compounds were resolved on a fabricated column using dynamic coating, including chiral alcohols, epoxides and amino acid derivatives. In addition, n‐alkanes, n‐alcohols and aromatic hydrocarbons have also been separated. [ABSTRACT FROM AUTHOR]

Herein, we reported a homochiral metal-organic frameworks (HMOF) [Nd3(D-cam)8(H2O)4Cl]n and prepared four novel chiral stationary phases (CSPs) in which two CSPs were fabricated by interfacial polymerization (IP). Some analytes were used to evaluate the separation performance of the two CSPs packed column. Moreover, the two CSPs also were tested under normal phase (NP), reverse phase (RP) and polar organic phase (POP) chromatography conditions and showed high column efficiency and selectivity especially for α-amino acids. Which seventeen and thirteen racemates were separated by the two CSPs (CSP-1, CSP-2). In contrast, only five and eight chiral compounds were separated in the CSP-3 and CSP-4, respectively. The experimental results showed that the HMOF [Nd3(D-cam)8(H2O)4Cl]n based novel CSPs possessed of good recognition ability for chiral separation in high-performance liquid chromatography (HPLC). [ABSTRACT FROM AUTHOR]

Metal-organic frameworks are promising porous materials. Chiral metal-organic frameworks have attracted considerable attention in controlling enantioselectivity. In this study, a homochiral metal-organic framework [Co2(D-cam)2(TMDPy)] (D-cam = d-camphorates, TMDPy = 4,4′-trimethylenedipyridine) with a non-interpenetrating primitive cubic net has been used as a chiral stationary phase in high-performance liquid chromatography. It has allowed the successful separation of six positional isomers and six chiral compounds. The good selectivity and baseline separation, or at least 60% valley separation, confirmed its excellent molecular recognition characteristics. The relative standard deviations for the retention time of run-to-run and column-to-column were less than 1.8 and 3.1%, respectively. These results demonstrate that [Co2(D-cam)2(TMDPy)] may represent a promising chiral stationary phase for use in high-performance liquid chromatography. [ABSTRACT FROM AUTHOR]

Initial efforts to combine a chiral metal-organic framework (MOF), Co( D-Cam)1/2(bdc)1/2(tmdpy) ( D-Cam= D-camphoric acid, bdc=1,4-benzenedicarboxylic acid, tmdpy=4,4′-trimethylenedipyridine), with peramylated β-cyclodextrins to investigate whether the use of a MOF can enhance enantioseparations on a cyclodextrin stationary phase are reported. Compared with columns of peramylated β-cyclodextrin incorporated in a MOF containing sodium chloride, the column of peramylated β-cyclodextrin+MOF shows excellent selectivity for the recognition of racemates, and higher resolutions are achieved on the peramylated β-cyclodextrin+MOF stationary phase. Experimental results indicate that the use of Co( D-Cam)1/2(bdc)1/2(tmdpy) can improve enantioseparations on peramylated β-cyclodextrins. This is the first report that chiral MOFs can improve enantioseparations on a chiral stationary phase for chromatography. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) have recently attracted considerable attention because of their fascinating structures and intriguing potential applications in diverse areas. In this study, we developed a novel method for determination of enantiomeric excess (ee) of (±)-1,1′-bi-2-naphthol by solid-phase extraction (SPE) using a chiral MOF, [Co(l-tyr)]n(l-tyrCo), as sorbent. After optimization of the experimental conditions, a good linear relationship between the ee and the absorbance of the eluate (R2 = 0.9984) was obtained and the standard curve was established at the concentration of 3 mmol L−1. The ee values of (±)-1,1′-bi-2-naphthol samples can be rapidly calculated using the standard curve after determination of the absorbance of the eluate. The method showed good accuracy, with an average error of 2.26%, and is promising for ee analysis. [ABSTRACT FROM AUTHOR]

• A homochiral POC CC19-R-based CSP was prepared by thiol-ene click reaction. • Various racemates have been well resolved in NP-HPLC and RP-HPLC. • Good complementarity with Chiralpak AD and Chiralcel OD on enantioseparation. • Enantioselectivity of chiral POCs-based CSPs have been significantly broadened. • Potential applications of chiral POCs for HPLC enantioseparation. In this study, a new chiral stationary phase (CSP) was fabricated by covalent bonding of a [4+6]-type homochiral porous organic cage (POC) CC19-R onto thiolated silica via a thiol-ene click reaction. The CC19-R was synthesized via Schiff-base reaction between 2-hydroxybenzene-1,3,5-tricarbaldehyde and (1 R , 2 R)-(-)-1,2-diaminocyclohexane. The enantioseparation capability of the resulting CC19-R-based CSP was systematically evaluated upon separating various chiral compounds or chiral pharmaceuticals in normal phase HPLC (NP-HPLC) and reversed phase HPLC (RP-HPLC), including alcohols, organic acids, ketones, diols, esters, and amines. Fifteen racemates were enantioseparated in NP-HPLC and 11 racemates in RP-HPLC. Some racemates have been well separated, such as 4-chlorobenzhydrol, cetirizine (in the form of dihydrochloride), 1,2-diphenyl-1,2-ethanediol, and 3-(benzyloxy)propane-1,2-diol whose resolution values reached 3.66, 4.23, 6.50, and 3.50, respectively. When compared with a previously reported chiral POC-based column (NC1-R column), eight racemates were not separated on the NC1-R column in NP-HPLC and five racemates were not separated in RP-HPLC, but were well resolved on this column, revealing that the enantioselectivity and separable range of chiral POCs-type columns could be significantly widened using this fabricated CC19-R column. Moreover, the resolution performance of the CC19-R column was also compared with commercial Chiralpak AD-H [CSP: Amylose tris(3,5-dimethylphenylcarbamate)] and Chiralcel OD-H [CSP: Cellulose tris(3,5-dimethylphenylcarbamate)] columns. The column also can separate some racemates that could not be separated or not well be separated by the two commercial columns, showing its good complementarity to the two commercial columns on chiral separation. In addition, the column also had good stability and reproducibility with the relative standard deviation (n = 5) of the retention time and resolution lower than 1.0% and 1.8%, respectively, after it had undergone multiple injections (100, 200, 300, and 400 times). This work indicated that the features of good resolution ability and simple synthesis methods using with this POC-based CSP provided chiral POCs with potential application prospects in HPLC racemic separation. [ABSTRACT FROM AUTHOR]

• A novel BINOL-based chiral polyimine macrocycle bonded silica CSP was prepared. • Excell enantioselectivity of the CSP in both NP-HPLC and RP-HPLC. • Good chiral separation complementarity to Chiralpak AD-H and Chiralcel OD-H columns. • Great potential of BINOL-based chiral macrocycle for HPLC enantioseparation. Macrocycles play vital roles in supramolecular chemistry and chromatography. 1,1′-Bi-2-naphthol (BINOL)-based chiral polyimine macrocycles are an emerging class of chiral macrocycles that can be constructed by one-step aldehyde-amine condensation of BINOL derivatives with other building blocks. These macrocycles exhibit good characteristics, such as facile preparation, rigid cyclic structures, multiple chiral centers, and defined molecular cavities, that make them good candidates as new chiral recognition materials for chromatographic enantioseparations. In this study, a BINOL-based [2+2] chiral polyimine macrocycle was synthesized by one-step condensation of enantiopure (S)-2,2′-dihydroxy-[1,1′-binaphthalene]-3,3′-dicarboxaldehyde with (1R,2R)-1,2-diaminocyclohexane. The product was modified with 5-bromo-1-pentene and then attached to thiolated silica using click chemistry to construct a new chiral stationary phase (CSP). The enantioselectivity of the new CSP was explored by separating various racemates under normal phase (NP) and reversed phase (RP) high performance liquid chromatography (HPLC). Thirteen racemates and eight racemates were enantioseparated under the two separation modes, respectively, including chiral alcohols, phenols, esters, ketones, amines, and organic acids. Among them, nine racemates achieved baseline separation under NP-HPLC and seven racemates achieved baseline separation under RP-HPLC. High resolution separation was observed with benzoin (Rs = 5.10), epinephrine (Rs = 4.98), 3-benzyloxy-1,2-propanediol (Rs = 4.42), and 4,4′-dimethylbenzoin (Rs = 4.52) in NP-HPLC, and with 4-methylbenzhydrol (Rs = 4.72), benzoin ethyl ether (Rs = 3.79), 1-phenyl-1-pentanol (R s = 3.68), and 1-(3-bromophenyl)ethanol (Rs = 3.60) in RP-HPLC. Interestingly, the CSP complemented Chiralcel OD-H, Chiralpak AD-H, and CYCLOBOND I 2000 RSP columns for resolution of these test racemates, separating several racemic compounds that could not be well separated by the three commercially available columns. The influences of injected sample amount on separation were also evaluated. It was found that the column exhibited excellent stability and reproducibility after hundreds of injections, and the relative standard deviations (n = 5) of the retention time and resolution were less than 0.49% and 0.69%, respectively. This study indicates that the BINOL-based chiral macrocycle has great potential for HPLC enantioseparation. [ABSTRACT FROM AUTHOR]

Metal organic cages (MOCs), as an emerging discrete supramolecular compounds, have received widespread attention in separation, biomedicine, gas capture, catalysis, and molecular recognition due to their porosity, adjustability and stability. Herein, we present a new chiral MOC FeII 4 L 4 coated capillary column prepared for gas chromatographic (GC) separation of different types of organic compounds, including n-alkanes, n-alcohols, alkylbenzenes, isomers, especially for racemic compounds. There are 20 different kinds of racemates (e.g., alcohols, ethers, epoxides, esters, alkenes, and aldehydes) were well resolved on the FeII 4 L 4 chiral column and a maximum resolution value for 1-phenyl-1-propanol reaches 6.17. The FeII 4 L 4 coated column exhibited high column efficiency (3100 plates m−1 for n-dodecane) and good enantiomeric resolution complementary to that of a commercial β-DEX 120 column and the previously reported chiral MOC [Fe 4 L 6 ] (ClO 4) 8 coated column. The relative standard deviation (RSDs) of the peak area and retention time of glycidol and nitrotoluene were below 1.2 %. This study reveals that chiral MOCs have good application prospects in chromatographic separation. Chiral MOC FeII 4 L 4 used for high-resolution gas chromatographic separation. [Display omitted] • A novel chiral MOC FeII 4 L 4 coated capillary column was prepared. • The FeII 4 L 4 coated column exhibited excellent separation performance for various mixtures and isomers. • The FeII 4 L 4 coated column offered high enantioselectivity and good resolution effect towards different types of racemates. [ABSTRACT FROM AUTHOR]

Macrocyclic compounds such as crown ethers and cyclodextrins play an important role in the field of chromatography and show excellent separation performance. The design of simple and convenient methods for the efficient synthesis of novel chiral macrocycles for chromatographic separation is of great significance. In this work, a novel chiral polyimine macrocycle (PIMC) was designed and synthesized by the simply one-step reaction of 2,6-diformyl-4- tert -butylphenol with (S)-(-)-1,2-propanediamine. Then, it was bonded onto silica by the thiol-ene click reaction to construct a new chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). The chiral separation performance of the proposed CSP was examined by separating various racemates in the normal-phase (NP) and reversed-phase (RP) HPLC. In total, twelve and nine racemates, including ethers, esters, amines, alcohols, organic acids, ketones, and epoxides, were separated to varying degrees via NP-HPLC and RP-HPLC, respectively, Moreover, the CSP offered good chiral separation complementarity to Chiralcel OD-H and Chiralpak AD-H columns for resolution of these test racemates, and it can separate several racemic compounds that either cannot be separated or cannot be separated well be separated by the two commercially available columns. After the column was used for hundreds of injections, the relative standard deviations of the retention time and resolution were below 0.56 % and 0.45 %, respectively, showing the good reproducibility and stability of the CSP. This study provides a simple and convenient approach to synthesize a novel chiral macrocycle and CSP and also indicates the broad application prospects of such chiral PIMCs in HPLC chiral separation. A new chiral polyimine macrocycle was designed and synthesized, and then bonded onto thiolated silica gel to prepare chiral stationary phase (CSP) for enantioseparation with excellent enantioselectivity in NP-HPLC and RP-HPLC. [Display omitted] • A new chiral macrocycle was simply synthesized by one-step reaction with high yield. • A novel chiral macrocycle-based CSP was prepared. • Excellent enantioselectivity of the CSP in normal-phase and reversed-phase HPLC. • Good chiral recognition complementarity to Chiralpak AD-H and Chiralcel OD-H columns. • Great potential of chiral polyimine macrocycles for HPLC enantioseparation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A chiral MOP [Cu 12 (L V) 12 (H 2 O) 12 ] as a novel stationary phase for GC separations. • The MOP coated column exhibited good resolution ability towards various enantiomers. • Multiple types of mixtures including n-alkanes, alkylbenzenes, n-alcohols, and isomers were well separated on the MOP coated column. Metal-organic polyhedra (MOPs), as a novel class of porous materials, exhibit distinctive application potential in molecular recognition, separation, catalysis, luminescent materials, drug delivery, and biomedicine owing to their tunable geometric shape and size, well-defined cavities, and discrete characteristics. In this study, we report that a chiral MOP [Cu 12 (L V) 12 (H 2 O) 12 ] (V = L-valine) coated capillary column was used for gas chromatographic separations. The MOP coated capillary column offered the efficient separation of n-alkanes, alkylbenzenes, n-alcohols, multiple types of isomers, and enantiomers with high selectivity. Various enantiomers including esters, halogenated hydrocarbons, alcohols, ethers, aldehydes, and amino acid derivatives were well resolved on this chiral column, especially for some amino acid derivatives (e.g., Rs = 5.24 for tyrosine derivative). Compared with the commercial β- DEX 120 column for separation of the tested racemates, the chiral resolution performance of the MOP coated column can be complementary to that of β -DEX 120 column. Using 1,2-dichloropropane and o, m, p -dichlorobenzene as analytes, the MOP coated column exhibited good stability and reproducibility for gas chromatographic separations. The relative standard deviations (RSDs) of the retention time and peak area for repeated separation of 1, 2-dichloropropane and o, m, p -dichlorobenzene were less than 1.15 and 0.79 %, respectively. The results show that the chiral MOP holds great potential as a novel type of CSP for application in gas chromatography. [ABSTRACT FROM AUTHOR]

Chiral capillary gas chromatography has been widely applied to separate volatile and thermally stable enantiomers due to its advantages of simplicity, high efficiency, fast analysis, good sensitivity, and absence of liquid mobile phases. In the first part of this article, recent research progress (from 2010 to the present) concerning newly developed chiral stationary phases based on cyclofructan derivatives and chiral porous materials, including metal-organic frameworks, covalent organic frameworks, inorganic mesoporous silicas, and molecular cages for use in gas chromatography, and the synthetic strategies for obtaining chiral porous materials, was reviewed. Finally, we discussed in detail the separation performances and chiral recognition mechanisms of novel chiral recognition materials coated on capillary columns towards various types of enantiomers, namely (1) amino acid derivatives; (2) alcohols, amines, and amino alcohols; (3) organic acids; (4) aldehydes and ketones; (5) ethers and epoxides, and (6) esters and other enantiomers. • Advances on various novel CSPs for GC enantioseparation were reviewed during 2010–2019. • The synthesis strategies to construct chiral porous materials were covered. • The resolution of different types of enantiomers on the novel CSPs was discussed. • The chiral recognition mechanisms between novel CSPs and chiral analytes were explained. • We summarize the advantages and disadvantages of novel CSPs used in GC. [ABSTRACT FROM AUTHOR]

• A novel chiral polyimine macrocycle (CPM) based CSP was developed for HPLC. • Good enantioselectivity of the CSP in both normal-phase and reversed-phase HPLC. • Enantioselectivity of such CPM type CSPs have been significantly broadened and improved. • Good complementarity to Chiralpak AD-H and Chiralcel OD-H columns in chiral separation. • Promising candidates of CPMs for HPLC enantioseparation. Chiral polyimine macrocycles (CPMs) constitute a new family of organic macrocycles that have defined cavities, rigid shapes, inherent chirality and multiple cooperative binding sites, and have shown great potential in diverse areas. However, the application of CPMs for high performance liquid chromatography (HPLC) enantioseparation has rarely been reported. In this work, a novel chiral stationary phase (CSP) for HPLC was prepared by chemical bonding of a CPM (C 54 H 72 N 6 O 3) onto thiolated silica via thiol-ene click reaction. The CSP exhibited good enantioselectivity in both normal- and reversed-phase HPLC. Chiral compounds included alcohols, diols, ketones, organic acids, esters, ethers, amines, and epoxides were enantioseparated on the column in normal-phase mode (17 compounds) and reversed-phase mode (20 compounds). Importantly, broader chiral resolution was observed with the column than that obtained using our previously studied chiral macrocycle H 3 L-based column, indicating the potential to significantly improve and broaden applicability of this novel macrocycle-type CSPs. Moreover, the CSP exhibited good complementary enantioseparation to Chiralpak AD-H and Chiralcel OD-H columns, enabling separation of some racemates that could not be separated by the two popular chiral HPLC columns. In addition, the fabricated column exhibited good stability and reproducibility. The relative standard deviations (RSDs) (n = 5) of retention time and resolution after multiple injections were < 0.20 % and < 0.39 %, respectively. The results demonstrated the great potential of this type of CPM for HPLC separation of enantiomers. [ABSTRACT FROM AUTHOR]

• A chiral porous organic cage based CSP was prepared by thiol-ene click reaction. • Good enantioselectivity of the CSP in both normal-phase and reversed-phase HPLC. • Various racemates have been well enantioseparated on the prepared CSP. • Enantiomers separation scope and applicability of POCs-based HPLC columns have been broadened. • Promising candidate of chiral porous organic cages for HPLC enantioseparation. Porous organic cages (POCs) are a new kind of porous molecular materials, which have gained widespread interest in many fields due to their intriguing properties, including excellent molecular solubility, inherent molecular cavity and rich host-guest chemistry. To date, many chiral POCs have been explored as chiral stationary phases (CSPs) for gas chromatographic (GC) separation of enantiomers. However, the applications of chiral POCs for high performance liquid chromatography (HPLC) enantiomeric separation is extremely rare. In this study, we report the construction of thiol-ene click reaction for the preparation of CSP for HPLC by using a [4+8]-type chiral POC NC4-R as chiral selector. The fabricated CSP showed good chiral resolution performance not only in normal-phase HPLC (NP-HPLC) but also in reversed-phase HPLC (RP-HPLC). Seventeen and ten racemates were well resolved in the two separation modes, respectively, including ketones, esters, alcohols, phenols, amines, ethers, organic acids, and amino acids. Moreover, the fabricated column also shows good chiral recognition complementarity to two popular chiral HPLC columns (Chiralpak AD-H and Chiralcel OD-H columns) and previously reported chiral POC NC1-R-based HPLC column, which can resolve some racemates that unable to be resolved by the two commercially available chiral HPLC columns and NC1-R-based column. The relative standard deviation (RSD) values (n = 4) of retention time and resolution (Rs) of analytes separated on the column were less than 0.3 % and 0.5 % after it was subjected to different injections, showing the good reproducibility and stability of the NC4-R-based column. This work demonstrated high potentials of chiral POCs for HPLC enantioseparation and the applicability of chiral POC-based HPLC columns can be broadened by developing more chiral POCs with diverse structures as chiral selector for HPLC. [ABSTRACT FROM AUTHOR]

• A novel chiral polyimine macrocycle-based CSP was prepared by click reaction. • The column shows good enantioselectivity in both normal-phase and reversed-phase HPLC. • Various racemates have been resolved on the fabricated column. • Great potential of chiral polyimine macrocycles for HPLC enantioseparation. Polyimine macrocycles are a new class of organic macrocycles with cyclic structures, well-defined molecular cavities, and multiple cooperative binding sites, which have recently aroused considerable research interest in molecular recognition and separation. Herein, we report the bonding of a [3+3] chiral polyimine macrocycle (H 3 L, C 78 H 78 N 6 O 3) on thiol-functionalized silica gel using thiol-ene click chemistry to prepare a chiral stationary phase (CSP) for high performance liquid chromatography (HPLC). The fabricated column exhibited excellent chiral separation capability under both normal-phase and reversed-phase conditions. Fourteen and 10 racemates were well resolved on the column in normal-phase mode (using n -hexane/isopropanol as the mobile phase) and reversed-phase mode (using methanol/water as the mobile phase), respectively, including alcohols, esters, ethers, ketones, aldehydes, epoxides and organic acids. Moreover, the column also shows good selectivity toward positional isomers. Six positional isomers (dinitrobenzene, chloroaniline, bromoaniline, iodoaniline, nitrobrobenzene and nitrochlorobenzene) were well separated on the column. In addition, the effects of the injection mass and mobile phase composition on the separation were investigated. The column shows good reproducibility and stability after multiple injections with the relative standard deviation (RSD) (n = 5) of the retention time and resolution being < 0.96 % and 0.65 %, respectively. This study indicates that this type of chiral polyimine macrocycles is a promising chiral selector for HPLC enantioseparation and will push forward the applications of more novel chiral macrocycles for chiral chromatographic separation. [ABSTRACT FROM AUTHOR]

Chiral covalent organic frameworks (CCOFs) have potential application in enantioseparation due to their advantages, such as large surface area, abundant chiral recognition sites and good chemical stability in organic solvents. However, the application of CCOFs in high performance liquid chromatography (HPLC) for enantioseparation has been rarely reported because of the shortcomings of CCOFs, such as light weight, irregular shape, and wide particle size distribution. In order to overcome the above shortcomings, a one-pot synthetic method was adopted to prepare a core-shell composite (β-CD-COF@SiO 2) via the growth of chiral β-CD COF on the surface of amino-functionalized SiO 2 microspheres. The as-prepared β-CD-COF@SiO 2 microspheres were used as a stationary phase for HPLC enantioseparation. The resolution ability of the β-CD-COF@SiO 2 -packed column toward various chiral compounds was investigated using n-hexane/isopropanol as the mobile phase. The results show that the chiral β-CD-COF@SiO 2 -packed column exhibited excellent chiral recognition ability for 24 pairs of chiral compounds with good reproducibility. These successful applications indicate that the preparation of the chiral COFs@SiO 2 core-shell microspheres as a novel stationary phase for enantioseparation has good application prospects in HPLC. [Display omitted] • A chiral core-sell β-CD-COF@SiO 2 microspheres composite was prepared using an in-situ growth strategy. • The β-CD-COF@SiO 2 core-shell microspheres as a novel chiral stationary phase was first applied for HPLC enantioseparation. • The packed column exhibited high enantioselectivity and excellent separation performance toward various racemates. [ABSTRACT FROM AUTHOR]

[Display omitted] • A [3 + 6] prismatic homochiral organic cage NC1-R was developed as stationary phase for GC with good separation performance. • Various racemates and organic isomers have been well separated on the NC1-R coated column. • The column exhibits prominent chiral recognition complementarity to commercial β-DEX 120 column. • Many racemates failed to be resolved on the commercial β-DEX 120 column but can be well resolved on the NC1-R coated column. • Good application prospects of NC1-R for GC separations. Porous organic cages (POCs) are a new class of advanced porous molecular materials, which are self-assembled from discrete, shape-persistent, cage-like molecules through relatively weak intermolecular forces. POCs have recently received extensive interest in diverse fields due to their noteworthy features of good solubility, unique pore structure, high stability, tunable pore size and volume, and so on. In this study, we report a [3 + 6] prismatic homochiral POC (NC1-R) as the stationary phase for preparing a capillary gas chromatographic (GC) column by a static coating method. Various types of mixtures have been well separated on the coated column, involving n -alkanes, n -alcohols, alkylbenzenes, positional isomers, structural isomers, and cis- / trans -isomers. Most importantly, the column also exhibits excellent chiral resolution capability for racemates. Twenty-three racemates, including alcohols, epoxides, esters, lactones, ethers, amino acid derivatives, amines, and sulfoxides, have been well resolved on the column. Among these racemates, about half (11 of the 23) could not be resolved on a commercial β-DEX 120 column (per- O -methylated β-cyclodextrin-based column), suggesting the advantageous performance of the present column. Furthermore, the fabricated column shows good reproducibility in terms of the retention times of analytes, with relative standard deviations (RSDs) in the ranges 0.02–0.19 %, 0.12–0.36 %, and 0.41–0.59 % for intra-day (n = 6), inter-day (n = 6), and column-to-column (n = 3), respectively, and good thermal stability at least up to 300 °C. This work demonstrates the good application prospects of NC1-R for GC separations, especially for GC enantioseparations. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal-organic frameworks (MOFs) have attracted a substantial amount of attention due to special properties, such as gas adsorption, chromatographic separation, and catalytic activity. Herein, a post-modification method was used to modify the surface of achiral MOFs using chiral polyaniline to synthesize a chiral core–shell composite (MIL-101@c-PANI), which was used for the first time as a stationary phase for the separation of chiral compounds. Twelve kinds of chiral compounds, including alcohols, ketones, esters, aldehydes, organic acids and amines were separated on the MIL-101@c-PANI packed column. Moreover, the column also showed good selectivity for the separation of positional isomers. Some chiral compounds that cannot be separated using a commercially available tris(3,5-dimethylphenylcarbamoyl) amylose-packed column (AD column), could be separated on the MIL-101@c-PANI column. The effects of the analyte mass and column temperature on the separation efficiency were investigated. The column exhibited good stability and reproducibility during the enantioseparation of chiral compounds. The MIL-101@c-PANI composite gives rise to a synergistic effect by combining the advantages of c-PANI and MIL-101, which is favorable for an improvement in the chiral separation performance. Therefore, this work shows that such composite materials will be very attractive in the field of separation science. [ABSTRACT FROM AUTHOR]