Li Zhang

Dynamic regulation of polymer solution phase behavior with real-time reversibility remains challenging. Here, we report a light-responsive poly(ethylene glycol) (PEG) system that enables reversible switching between linear and cyclic topologies, allowing continuous modulation of thermally induced phase transitions. Linear PEG functionalized with styrylpyrene end groups undergoes efficient intramolecular [2 + 2] photocycloaddition under visible light to form cyclic polymers, while UV irradiation restores the linear precursor. This reversible topology interconversion allows continuous tuning of the cyclic/linear ratio. As a result, the cloud point temperature of aqueous solutions can be modulated over a wide range from 37 to 65 °C. Aggregation appears to be enhanced in linear polymers through end-group-mediated π-π stacking and intermicellar bridging, whereas it is suppressed in cyclic polymers due to topological constraints and reduced stacking interactions. This work establishes topology switching as a noninvasive strategy for dynamically regulating polymer solution thermodynamics and highlights topology as a tunable parameter for controlling thermoresponsive behavior.

In recent years, the development of high-performance membranes for seawater desalination has attracted significant attention. This work proposes a novel model by employing a boron nitride nanotube (BNNT) as a support in lamellar boron nitride (BN) membranes. The effects of structural parameters as well as the role of nanotubes on seawater desalination performance are explored systematically via nonequilibrium molecular dynamics simulations (NEMD). In addition, the transport mechanism for water molecules and the separation mechanism for ions transmitted through the BN-BNNT membranes are elucidated at the molecular level. Simulation results indicate that the BN-BNNT membrane exhibits a higher water flux rate compared to the BN membrane. Additionally, reducing the gap width from 10 Å to 8 Å leads to a higher ion rejection rate but a significant decrease in water flux rate. The rejection rates for Na⁺ and Cl^- ions are promoted by increasing the interlayer spacing to larger values. This phenomenon can be attributed to the trapping of water molecules and hydration ions in the interfacial regions formed between the BN and BNNT nanosheets. It is possible to simultaneously increase the water flux and interception by inserting nanotubes and adjusting the distance of the interlayer spacing. This study suggests that the stability of lamellar nanomembranes can be enhanced through the incorporation of nanotubes as a support. Simultaneously, it is possible to enhance the rejection rate in such membranes without decreasing the water flux rate by adjusting the relevant structural parameters.

Selective extraction of KCl from complex salt lake brines remains a challenging task due to the presence of competing ions and the high energy requirements of conventional separation methods. To overcome these limitations, we have developed a biomimetic separation system that integrates three-dimensional (3D) covalent organic framework (COF) membranes with redox-mediated energy harvesting. These COF membranes are designed with sub-nanometer cavity channels decorated with oxygen-containing groups, which enable fine-tuning of electrostatic potential. This design allows for the simultaneous separation of anions and cations through valence-dependent short-range interactions. By coupling the COF membranes with Ag/AgCl redox pairs, the system converts the salinity gradient across the membrane into an internal electric field, facilitating autonomous ion transport without the need for external energy input. The system achieves over fivefold higher flux rates for K⁺ and Cl⁻ (2.6 and 3.2 mol m^–2 h^–1, respectively) and demonstrates outstanding separation performance with Cl^–/SO₄^2– = 332, K⁺/Mg²⁺ = 60, K⁺/Na⁺ = 7, and K⁺/Li⁺ = 11, substantially exceeding the passive diffusion ratios of 253, 27, 3, and 5, respectively. This work presents a sustainable, scalable approach for extracting valuable resources from complex brines, combining innovative biomimetic membrane design with redox-assisted process engineering, offering a promising solution to the energy and selectivity challenges in industrial ion separation.

A convergent approach for the enantioselective construction of an advanced intermediate containing the [5,5,6,6]-tetracyclic core framework of the khayanolide-type limonoids was described. The strategy features an acylative kinetic resolution of the benzylic alcohol, a 1,2-Grignard addition and an AcOH-interrupted Nazarov cyclization.

With the rapid development of nanotechnology, functionalized graphene membranes have shown great advantages, attracting increasing attention in recent years. However, the effects of different groups on the desalination performance of layered graphene membranes, as well as the transport and separation mechanisms of water molecules and ions within two-dimensional nanochannels, remain insufficiently understood. In this study, molecular dynamics simulations are employed to investigate the influence of multiple factors on seawater desalination performance, focusing on transport behavior and intermolecular interactions, to elucidate the structure–performance relationship between the membrane architecture and separation efficiency. Our findings indicate that the desalination performance of a multilayer stacked graphene oxide membrane (MGOM) is affected by key structural parameters, including interlayer spacing (H), offset (O), and slit width (dG). Optimal performance is achieved when H = 0.8 nm, dG = 1.1 nm, and O = 1.26 nm. Interestingly, the rejection rate of Na⁺ is slightly lower than that of Cl⁻, mainly due to the differences in the interaction between different ions and functional groups in the sheets and the hydration radius.

A convergent approach for the enantioselective construction of an advanced intermediate containing the [5,5,6,6] tetracyclic core framework of the khayanolide-type limonoids was described. The strategy features an acylative kinetic resolution of the benzylic alcohol, a 1,2-Grignard addition and an AcOH-interrupted Nazarov cyclization.

Advancing membranes with enhanced solute-solute selectivity is essential for expanding membrane technology applications, yet it presents a notable challenge. Drawing inspiration from the unparalleled selectivity of biological systems, which benefit from the sophisticated spatial organization of functionalities, we posit that manipulating the arrangement of the membrane’s building blocks, an aspect previously given limited attention, can address this challenge. We demonstrate that optimizing the face-to-face orientation of building blocks during the assembly of covalent-organic-framework (COF) membranes improves ion-π interactions with multivalent ions. This optimization leads to extraordinary selectivity in differentiating between monovalent cations and anions from their multivalent counterparts, achieving selectivity factors of 214 for K ⁺ /Al ³⁺ and 451 for NO ₃ ⁻ /PO ₄ ³⁻ . Leveraging this attribute, the COF membrane facilitates the direct extraction of NaCl from seawater with a purity of 99.57%. These findings offer an alternative approach for designing highly selective membrane materials, offering promising prospects for advancing membrane-based technologies.

Efficient energy conversion using ions as carriers necessitates membranes that sustain high permselectivity in high salinity conditions, which presents a significant challenge. This study addresses the issue by manipulating the linkages in covalent-organic-framework membranes, altering the distribution of electrostatic potentials and thereby influencing the short-range interactions between ions and membranes. We show that a charge-neutral covalent-organic-framework membrane with β-ketoenamine linkages achieves record permselectivity in high salinity environments. Additionally, the membrane retains its permselectivity under temperature gradients, providing a method for converting low-grade waste heat into electrical energy. Experiments reveal that with a 3 M KCl solution and a 50 K temperature difference, the membrane generates an output power density of 5.70 W m⁻². Furthermore, guided by a short-range ionic screening mechanism, the membrane exhibits adaptable permselectivity, allowing reversible and controllable operations by finely adjusting charge polarity and magnitude on the membrane’s channel surfaces via ion adsorption. Notably, treatment with K₃PO₄ solutions significantly enhances permselectivity, resulting in a giant output power density of 20.22 W m⁻², a 3.6-fold increase over the untreated membrane, setting a benchmark for converting low-grade heat into electrical energy.