Widespread in the natural world, chirality is the unique property of a substance whose geometric form cannot coincide with its mirror image [1,2]. Among various chiral compounds, chiral drugs, chiral pesticides, chiral catalytic intermediates and chiral additives play an increasingly important role in medicine, agriculture, chemistry and life [3]. However, different configurations of chiral drugs can exhibit different pharmacological activities [4], resulting in enantiomers can exhibit different pharmacokinetic and pharmacodynamics profiles. Ignoring these differences will affect the safety assessment of chiral drugs. As one of the most widely used drugs in the world, different configurations of chiral drugs exhibit different properties. For example, (S)-ibuprofen has a major role, (R)-ibuprofen is less active but has pharmacology related to anti-inflammatory effects [5]. (S)-ketoprofen has analgesic and anti-inflammatory effects compared to the (R)-ketoprofen [6]. (S)-flurbiprofen can be used to treat arthritis, while (R)-flurbiprofen has an important function in the treatment of Alzheimer's disease [7]. And single-configuration enantiomers of chiral drugs have enhanced efficacy and safety compared with racemates. Therefore, it is very important to obtain single enantiomers of chiral drugs and to study drugs activity at the level of single enantiomers [[8], [9], [10]]. This will reduce high drug consumption and drug damage, while meeting the concept of efficient and eco-friendly social development, and has great research value for clinical medicine and biopharmaceuticals.

The increased demand for single-configuration enantiomers has contributed to the rapid development of enantioseparation techniques [11,12]. Currently, the main methods for obtaining single-configuration enantiomers include natural sources [13], asymmetric synthesis [14], crystalline separation [15], membrane separation [16], enzymatic methods [17] and chromatographic separation [18]. Notably, chromatography has emerged as one of the most efficient techniques for separating directly single-configuration enantiomers by optically active ambient chiral mobile phases or CSPs. This separation technique is based on the differences in forces between CSPs and different configurations of chiral molecules. Moreover, the enantioselectivity with CSPs is ascribed to energetic differences in the selector-enantiomeric selectands associations [19,20]. As the core of chromatography, CSPs have great potential in development and application. In recent years, different CSPs including covalent organic frameworks (COFs) [21], metal-organic frameworks (MOFs) [22], porous organic cages (POCs) [23], polysaccharides [24] and antibiotics [25] have been widely applied for chiral recognition and separation. However, the development of novel CSPs for enantioseparation still needs further research due to irreconcilable and difficult to control chiral selectivity [26]. Among them, supramolecular macrocycles possess abundant chiral sites that can form different complexes with enantiomers, thus realizing highly selective separation of enantiomers. In particular, as a new generation of supramolecular macrocyclic subjects following crown ethers [27], cyclodextrins [28], calixarenes [29] and cucurbiturates [30], pillar[5]arenes have the unique repeating structural units, electron-rich hydrophobic cavities [31] and easy functionalization [32,33]. The novel chiral stationary phases can be prepared by introducing chiral groups into the cavity of pillar[5]arenes or inhibiting the inversion of its planar conformations [[34], [35], [36], [37], [38], [39]]. To date, histidine and its derivatives have been included in many CSPs as chiral selectors, and principally in those ones used for chiral ligand-exchange chromatography (CLEC) applications [40]. Due to its ability to fully preserve complexation properties as a chiral selector [41], the imidazole ring in the structure enhances π-π interactions, and low steric hindrance, histidine has attracted much attention in the study of novel CSPs.

In order to expand the application of pillar[5]arene in chiral stationary phase, we introduced L/D-histidine containing imidazole conjugated ring into pillar[5]arene-functionalized mesoporous silica to prepare L/DHis-BP5-Sil, aiming at improving the enantioseparation ability. The L/DHis-BP5-Sil can take advantage of multiple chiral sites to achieve highly selective separation of different enantiomers. Simultaneously, we studied the effects of mobile phase ratio, flow rate and temperature on the resolution (Rs) values of enantiomers, which provided a new idea for the development of chiral stationary phases.