Lijia Liu

The development of novel enantioselective organocatalysts is a captivating area in chiral chemistry. Herein, the chiral porous hypercrosslinked polymer precursor, HCP-AA-Fmoc-(L)Pro, was prepared via a Friedel-Crafts alkylation reaction. Notably, in addition to serving as a protective group, the fluorenyl moiety of Fmoc group undergoes co-crosslinking with the benzene rings of the aromatic amines within the hypercrosslinked polymer framework, thereby constructing a sterically stable environment. Subsequently, based on the deprotection of the 9-fluorenylmethyloxycarbonyl (Fmoc) group, a sidearm group was introduced in situ at the catalytic site, and the chiral hypercrosslinked proline-derived polymer catalysts HCP-AA-DBFBB-(L)Pro was synthesized. By introducing dynamic steric hindrance to finely tune the chiral environment, the chiral cavity accommodating substrates and reagents was modulated. This enabled high activity in the asymmetric aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, achieving impressive dr values of up to 99/1 and ee values of 96%. Moreover, the HCP-AA-DBFMO-(L)Pro exhibited high enantioselectivities in various asymmetric reactions, including aldol reaction, Michael addition reaction, and domino reaction. This study provides new insights into the development and construction of chiral organocatalysts, wherein the introduction of the side arm facilitates high enantioselectivity.

Membranes with excellent chlorine resistance are required for stable operation and long service life. Traditional polyamide (PA) nanofiltration (NF) membranes typically suffer from inadequate chlorine resistance. To overcome this critical challenge and the long-standing problem of insufficient permeability, a novel polyesteramide (PEA) NF membrane was fabricated. Specifically, naringin (NG), a naturally occurring polyphenol rich in hydroxyl groups, was introduced as a co-monomer with piperazine (PIP) in the aqueous phase for interfacial polymerization with trimesoyl chloride (TMC) in the organic phase. The chlorine-susceptible amide groups were partially substituted by intrinsically chlorine-resistant ester groups in the fabricated PEA membrane. As a result, the chlorine resistance of the PEA membrane was greatly enhanced, with Na2SO4 rejection remaining above 93 % after exposure to 20,000 ppm·h of free chlorine. The resulting PEA membrane exhibited reduced surface roughness and selective-layer thickness, coupled with a slight increase in pore size and free volume fraction, which was attributed to intermolecular interactions between NG and PIP in the aqueous phase. Consequently, the PEA membrane demonstrated a water flux approximately twice that of the PA membrane, while maintaining a high Na2SO4 rejection rate of 99 % and rejecting more than 98 % of various antibiotics (e.g., cephalosporins and tetracyclines). Furthermore, the PEA membrane exhibited favorable antifouling performance, satisfactory anti-swelling property, and filtration stability under various conditions.

Covalent organic framework (COF) membranes with high porosity and ordered channels possess significant potential for the removal of organic micropollutants from wastewater, offering ultrafast water permeability. The present study proposes the construction of a novel COF based composite membrane for the purpose of improving the selectivity of dye/salt separation. The COF layer was initially fabricated via interfacial polymerization using 1,3,5-triformylbenzene and m-phenylenediamine on the hydrolyzed polyacrylonitrile (HPAN) substrate, and then the in-situ growth of a metal-phenolic network (MPN) layer occurred through the complexation of the small-molecule polyphenolic compound of epigallocatechin gallate (EGCG) with Cu²⁺ on the COF layer. The combination of the Cu-EGCG based MPN layer and the COF layer was demonstrated to enhance the compactness, charge properties, and hydrophilicity of the selective layer. The fabricated Cu-EGCG/COF/HPAN membrane demonstrated remarkable performance in the selective separation of dye/salt, exhibiting rejection rates for Congo Red and NaCl of 98.8% and 11.6%, respectively, and a high water permeance of 50.6 L m⁻² h⁻¹ bar⁻¹. In addition, the fabricated membrane exhibited separation stability in the long-term filtration process and demonstrated outstanding anti-fouling performance, with a flux recovery rate of 88.8%. This work presented a strategy that has the potential to facilitate the construction of high performances COF based membranes.

Thermosetting epoxy resins with low dielectric loss and high thermal stability are highly desirable for high-frequency electronic applications, yet these properties remain difficult to balance because reducing polarity in conventional curing systems often compromises intermolecular cohesion. Herein, a series of vinyl-functionalized active esters were synthesized to introduce a programmable vinyl-mediated curing motif into epoxy thermosets. Spectroscopic and calorimetric analyses revealed that ester–epoxy coupling dominated the early curing stage, generating a low-polarity primary network, whereas vinyl crosslinking remained kinetically suppressed until higher temperatures and conversion levels were reached. This programmed “epoxy-first, then vinyl” curing pathway subsequently enabled delayed vinyl polymerization to lock the pre-formed epoxy matrix, thereby generating a hierarchically organized crosslinked network. As a result, the optimized thermoset exhibited a dielectric constant of 2.90 and a dielectric loss of 0.0051 at 10 GHz, together with a high glass-transition temperature of 198 °C, a reduced coefficient of thermal expansion of 54.7 ppm K⁻¹, and a tensile strength of 65.2 MPa. Dynamic mechanical, thermomechanical, and thermal analyses further suggested enhanced molecular confinement and increased crosslink density induced by the late-stage polyvinyl network locking process. Overall, these findings show that programmed sequential curing can serve as a promising route to alleviate the conventional trade-off between dielectric and thermal–mechanical properties, providing a useful strategy for designing low-loss thermosetting dielectrics through network evolution control rather than simple compositional modification.

Covalent organic framework (COF) membranes with high porosity and ordered channels possess significant potential for the removal of organic micropollutants from wastewater, offering ultrafast water permeability. The present study proposes the construction of a novel COF based composite membrane for the purpose of improving the selectivity of dye/salt separation. The COF layer was initially fabricated via interfacial polymerization using 1,3,5-triformylbenzene and m-phenylenediamine on the hydrolyzed polyacrylonitrile (HPAN) substrate, and then the in-situ growth of a metal-phenolic network (MPN) layer occurred through the complexation of the small-molecule polyphenolic compound of epigallocatechin gallate (EGCG) with Cu2+ on the COF layer. The combination of the Cu-EGCG based MPN layer and the COF layer was demonstrated to enhance the compactness, charge properties, and hydrophilicity of the selective layer. The fabricated Cu-EGCG/COF/HPAN membrane demonstrated remarkable performance in the selective separation of dye/salt, exhibiting rejection rates for Congo Red and NaCl of 98.8% and 11.6%, respectively, and a high water permeance of 50.6 L m−2 h−1 bar−1. In addition, the fabricated membrane exhibited separation stability in the long-term filtration process and demonstrated outstanding anti-fouling performance, with a flux recovery rate of 88.8%. This work presented a strategy that has the potential to facilitate the construction of high performances COF based membranes.

Membranes with excellent chlorine resistance are required for stable operation and long service lifespan. Traditional polyamide (PA) nanofiltration (NF) membranes typically suffer from inadequate chlorine resistance. To address this critical challenge, coupled with the unresolved issue of insufficient permeability, a novel polyesteramide (PEA) NF membrane was fabricated. Specifically, naringin (NG), a naturally occurring polyphenol abundant in hydroxyl groups, was introduced as a co-monomer with piperazine (PIP) within the aqueous phase to interfacial polymerization along with trimesoyl chloride (TMC) within the organic phase. The chlorine susceptible amide groups were partially substituted by intrinsically chlorine resistant ester groups in the fabricated PEA membrane. Therefore, the chlorine resistance of the PEA membrane was greatly enhanced (with the Na2SO4 rejection maintaining above 95% following exposure to 10,000 ppm·h of free chlorine). The resulting PEA membrane exhibited reduced surface roughness and selective layer thickness, coupled with a slight increase in pore size and free volume fraction, contributing to the interaction between NG and PIP in the aqueous phase. Consequently, the PEA membrane demonstrated a water flux that was twice that of the PA membrane, while maintaining a high Na2SO4 rejection rate of 99% and exceeding 98% rejection for various antibiotics (e.g., cephalosporins and tetracyclines). Furthermore, the PEA membrane exhibited remarkable antifouling performance and enduring operational stability.

High-throughput DFT and interpretable ML identify Zr/g-C ₂ N and Ti/g-C ₂ NC as highly active and selective NO ₃ RR catalysts, suppressing HER and side reactions with limiting free-energy changes of 0.30 and 0.34 eV, respectively.

Applications of porous carbon materials for electromagnetic wave absorption have been extensively documented. Nonetheless, the limited electromagnetic loss mechanisms impede the attainment of superior absorption performance. In this study, an...