•The fabricated Glu-modified GO (Glu-GO) membranes were used into chiral separations.•Glu-GO membranes exhibited high flux with a 1–2 orders of magnitude enhancement.•Glu-GO membranes exhibited high selectivity (the maximum exceeds 2.0).•This is the first report on GO-based membranes for chiral separations.The primary aim of this investigation was to achieve chiral separations via fabricating graphene oxide (GO) based membranes with high separation performances, derived from incorporating a chiral selector (L-Glutamic acid) into GO flakes, based on considerations of GO membranes having the inherently high throughput nature. The GO membrane was fabricated via a simple vacuum filtration method, in which L-Glutamic acid not only provided the stacked GO nanosheets with the necessary stability to overcome their inherent dispensability in water environment but also finely tuned spacing of the GO nanosheets and the resulting performance. The corresponding membrane structure together with GO and amino acid modified GO nanosheets was systematically characterized by SEM, TEM, AFM, XPS, XRD, FT-IR and so on. Finally, enantioseparation performances of amino acid modified GO membranes toward 3, 4-Dihydroxy-D, L-phenylalanine were detected. Results show that such membranes exhibit extraordinary chiral resolution properties, which are 1−2 orders of magnitude higher in the flux and greater in selectivity, compared to common chiral separation membranes. Our findings demonstrate that the modified GO membranes might provide another general approach to simultaneously facilitate high-flux and high-selectivity for a host of enantio- and bio-separations.Chemical modification of graphene oxide (GO) flakes by incorporating chiral selectors can offer GO membranes extraordinary chiral separation performances, which exhibit a higher flux and a competitive selectivity, compared with the conventional membrane separation method. GO-based membranes show a great potential in the application of chiral separation.

The pH-controlled crystal growth of two complexes with different coordination modes, derived from gemini surfactant molecules with a bipyridyl spacer (12Bpy) and metal copper ions (Cu2+) is presented in this work. Such crystalline forms obtained in appropriate pH ranges exhibit dissimilar morphologies, colors and crystalline structures. Under weak acidic conditions with a slightly higher pH (>4.3), blue grain crystals, made from dihydroxo-bridged binuclear complexes with a square pyramidal coordination mode, are formed, whereas under slightly stronger acidic conditions (pH <3.8 in this work), green crystals with mononuclear complexes with a distorted trigonal bipyramidal geometry are readily fabricated, and meanwhile the blue crystals are completely inhibited. In particular, these two crystals concomitantly existed in an intermediate pH range of 3.8–4.3. We suggest a fivefold coordinated Cu(II)/12Bpy complex with a 1 : 1 metal–ligand ratio and three hydrated water ligands and a pH-controlled crystal growth mechanism on the basis of UV-vis spectra and density functional theory (DFT) calculations. Our findings indicate that pH adjustment is a straightforward and efficient way to control the crystal growth, having potential application in the preparation of smart and multifunctional materials.

We present a novel porous molecular crystal (PMC) constructed using metal complexes, which shows a striking feature, namely that such a crystal exhibits a reversible transition in the crystal structure when subjected to water removal/uptake cycles. It was found that the dehydrated crystal adsorbed a given quantity of water, that is, each complex assembling block, derived from two gemini surfactant molecules with a bipyridyl spacer and two copper ions (Cu2+) coordinated, stuck to 10 molecules of water. Also, the water included in crystals might generate a unique two-dimensional (2D) hydrogen bond network, including metal–ligand complex units, counter ions and crystalline water. Specially, the crystalline structure was not destroyed upon desolvation, which is ascribed to the metal ion introduced as well as the counter ion (Br−) providing additional electrostatic interactions and hydrogen bonds. Our findings indicate that the introduction of metal ions may provide an alternative to the common weak interactions when designing PMCs. In addition, this crystal material is sensitive to moisture, extending the scope of such a gemini species for potential applications in chemical sensors and in humid environments.

A novel gemini amphiphile bearing a rigid spacer was found to form inclusion crystals with water in 1:3 host-to-guest molar ratios. The host molecules can generate a hydrophobic cavity unit via intermolecular intersections between each two neighbouring molecules, which can be connected with one another in one direction, finally resulting in a channel. At the same time, one-dimensional (1D) water chains are trapped in the channels by weak C–H⋯O, O–H⋯Br− and C–H⋯Br− interactions with the walls composed of the host molecules. These interactions and water chains together with the alternating water chain and host molecule layers can form a two-dimensional network in the crystal, which can stabilise the crystal structure. The profound contribution of the water chains to the stability of the host framework is verified by comparisons of properties between water-containing crystals and anhydrous materials. Meanwhile, weak interactions are theoretically calculated and visualised by non-covalent interaction (NCI) analysis and further confirmed by spectral experiments. Both experiment and calculation reveal that these weak hydrogen bonds provide cohesion that is vital to crystal stability.

We have synthesized four atropisomers of the pivalamido phenyl substituted porphyrins, α,α,α,β-PivPP (abbreviation of meso-α,α,α,β-tetra(o-pivalamidophenyl)porphyrin), α,β,α,β-PivPP, α,α,β,β-PivPP and α,α,α,α-PivPP. The latter one is usually called the “picket-fence” substituted porphyrin. The interfacial behaviors of the four compounds have been studied by using Langmuir–Blodgett (LB) technique, Ultraviolet–visible (UV–vis) and Atomic Force Microscopy (AFM). The obtained π–A isotherms show that the Langmuir monolayers of PivPPs are formed at the air/water interface except that of α,α,β,β-PivPP which exhibits a platform at the surface pressure in the range of 11–14 mN/m indicating a monolayer transition. The UV–vis spectra disclose that the red-shift happens in the porphyrin Soret bands of the four atropisomer LB films deposited on quartz slides compared with the corresponding absorption bands in the diluted chloroform solution, which results from the strong π–π interaction between porphyrin rings. Except for α,α,β,β-PivPP, AFM images also suggest that the LB films formed by atropisomers of the substituted porphyrin are homogeneous monolayer. Generally, film-forming molecules pack more tightly during compressing the mononlayers, which is consistent with the UV–vis spectra results that the absorption intensities of LB films enhance and the Soret band varies with the increase of surface pressure. On the other hand, AFM morphologies of α,α,β,β-PivPP at higher surface pressure reveal that bilayers are formed, which coincides with the presence of a platform in the π–A isotherm.Graphical abstractThe graph shows the arrangement of four atropisomers of α,α,α,α-PivPP, (a) α,α,β,β-PivPP, (b) α,β,α,β-PivPP, (c) α,α,β,β-PivPP, and (d) α,α,α,α-PivPP; green ball means the trimethyl groups with the steric hindrance, while yellow ball without the steric hindrance.Research highlights▶ Four atropisomers of α,α,α,α-PivPP are synthesized and separated by a special method. ▶ The Langmuir monolayers of PivPPs are formed at the air/water interface except α,α,β,β-PivPP, which demonstrate the bilayer forms. ▶ α,α,β,β-PivPP monolayer is the most instable among the four atropisomers due to that four pivalamido groups of α,α,β,β-PivPP have less steric hindrance.

Mixed Langmuir−Blodgett (LB) films composed of a cationic gemini surfactant, [C18H37(CH3)2N+−(CH2)s−N+(CH3)2C18H37],2Br− (18-s-18 with s = 3, 6, 8, 10 and 12), and a fatty acid of stearic acid (SA) were studied by the π−A isotherm measurement, as well as by AFM and FT-IR. The analysis of the mean molecular area, the excess area and the excess Gibbs free energy from π−A isotherms suggests the existence of attractive interactions between 18-s-18 and SA molecules in the mixed monolayers. The spacer group of 18-s-18 plays a very important role in the surface properties of 18-s-18/SA mixed monolayers. When s ≤ 8, 18-s-18 and SA are completely miscible, while partially miscible mixed monolayers are presented when s > 8. Especially, in the latter case, when s = 12, phase separation appears in two composition regions of XSA = 0.4−0.75 and XSA = 0.75−0.85, respectively. This miscible phenomenon is confirmed by AFM observation. The result of FT-IR indicates that when XSA ≤ 0.67, SA could ionize completely and form a “cationic−anionic surfactant” with 18-s-18 owing to the electrostatic interaction between the head groups, while when XSA > 0.67, SA only partially ionizes, −COO− and −COOH coexist in mixed monolayers.