Lipase-based MIL-100(Fe) biocomposites as chiral stationary phase for high-efficiency capillary electrochromatographic enantioseparation

Proportionally controlled dual-chiral covalent organic frameworks via thiol-ene click reaction for efficient enantioseparation

Developing a universally applicable and commercially hopeful chiral material is a significant challenge for the separation and analysis field. In this study, innovative dual-chiral CCOFs ([SH-β-CD-NALC]x-COFs) modified with 6-deoxy-6-mercapto-β-cyclodextrin (SH-β-CD) and N-acetyl-l-cysteine (NALC) are presented. These CCOFs were synthesized using a single, one-step bottom-up approach at room temperature, specifically designed for enantiomer recognition and separation. We investigated the effect of varying ratios of multiple chiral selectors in CCOFs on chiral recognition abilities through adsorption experiments for the first time. The precisely engineered [SH-β-CD-NALC]1/6-COF, with excellent stability, crystallinity, abundant chiral sites, and a greater specific surface area, was well suited as a chiral stationary phase (CSP) in various racemates separation. The results showed satisfactory resolution, column efficiency, stability, and reproducibility. In addition, mechanism studies have revealed that the dual-chiral COF can offer triple selectivity and achieve the effect where 1 + 1 is greater than 2. This work emphasized the advantages of dual-chiral COF in achieving racemic drug separation, providing a new approach for the development of high-performance chiral separation platforms in the future.

Construction and Application of a Pepsin-Functionalized Covalent Organic Framework with Prominent Chiral Recognition Ability

The stable Pepsin@covalent organic framework (Pepsin@COF) were constructed base on matching COF pore diameter to pepsin dimension. It exhibits excellent chiral recognition capabilities (e. e. % up to 62.63 %) and potential for enantioseparation. Furthermore, a positive correlation between the immobilized enzyme activity and chiral recognition was revealed, offering insights for the design of biocatalytic nanosystems in chiral separation.

Easy and Versatile Technique for the Preparation of Stable and Active Lipase-Based CLEA-like Copolymers by Using Two Homofunctional Cross-Linking Agents: Application to the Preparation of Enantiopure Ibuprofen

An easy and versatile method was designed and applied successfully to obtain access to lipase-based cross-linked-enzyme aggregate-like copolymers (CLEA-LCs) using one-pot, consecutive cross-linking steps using two types of homobifunctional cross-linkers (glutaraldehyde and putrescine), mediated with amine activation through pH alteration (pH jump) as a key step in the process. Six lipases were utilised in order to assess the effectiveness of the technique, in terms of immobilization yields, hydrolytic activities, thermal stability and application in kinetic resolution. A good retention of catalytic properties was found for all cases, together with an important thermal and storage stability improvement. Particularly, the CLEA-LCs derived from Candida rugosa lipase showed an outstanding behaviour in terms of thermostability and capability for catalysing the enantioselective hydrolysis of racemic ibuprofen ethyl ester, furnishing the eutomer (S)-ibuprofen with very high conversion and enantioselectivity.

Dual-ligand 3D lammelar chiral metal-organic framework for capillary electrochromatographic enantioseparations

Dual-ligand metal-organic frameworks (MOFs) based on tryptophan and camphoric acid were designed and synthesized as the stationary phase of the capillary electrochromatography (CEC) system. This CEC system showed significantly improved enantioseparation ability for nine drugs, compared with the single-ligand MOF stationary phase. Characterization methods such as N₂ adsorption-desorption isotherms and scanning electron microscopy proved that the dual-ligand MOFs possessed excellent 3D spatial structures (ligand ratio is 1:1) which ensured the enantioseparation capability of the CEC system. The influence of ligand types on the chiral selectivity of MOFs was explored using racemic phenylalaninol and its single enantiomers as models. When the chiral type of the ligands is consistent, the enantioseparation ability of the CEC system is better. The chromatographic conditions such as buffer concentration, buffer pH, organic solvent addition ratio, and applied voltage were optimized, and satisfactory repeatability and stability of the CEC system were verified. Additionally, the enantioseparation mechanism of the CEC system was discussed through adsorption kinetic experiments, adsorption isotherm fitting, and thermodynamics.

Engineering Metal-Organic-Framework (MOF)-Based Membranes for Gas and Liquid Separation

Separation is one of the most energy-intensive processes in the chemical industry, and membrane-based separation technology contributes significantly to energy conservation and emission reduction. Additionally, metal-organic framework (MOF) materials have been widely investigated and have been found to have enormous potential in membrane separation due to their uniform pore size and high designability. Notably, pure MOF films and MOF mixed matrix membranes (MMMs) are the core of the "next generation" MOF materials. However, there are some tough issues with MOF-based membranes that affect separation performance. For pure MOF membranes, problems such as framework flexibility, defects, and grain orientation need to be addressed. Meanwhile, there still exist bottlenecks for MMMs such as MOF aggregation, plasticization and aging of the polymer matrix, poor interface compatibility, etc. Herein, corresponding methods are introduced to solve these problems, including inhibiting framework flexibility, regulating synthesis conditions, and enhancing the interaction between MOF and substrate. A series of high-quality MOF-based membranes have been obtained based on these techniques. Overall, these membranes revealed desired separation performance in both gas separation (e.g., CO2, H2, and olefin/paraffin) and liquid separation (e.g., water purification, organic solvent nanofiltration, and chiral separation).