Science China Chemistry最新文献

Sodium-ion batteries (SIBs) hold great promise to be the next-generation large-scale energy storage system due to their cost-effectiveness and resource availability. More importantly, sodium-ion batteries have energy density approaching that of lithium-ion batteries, outperforming most of their counterparts. Further improvement of their energy density depends on the innovation of high-capacity layered sodium-ion cathodes, which entails the participation of anionic redox whose origin and reversibility are closely associated with the superstructures in the transition metal layer. Recently, various superstructures were found in layered sodium-ion cathodes and were tightly correlated with their anionic redox activity and electrochemistry. Given its high importance in tailoring the performance of sodium-ion cathodes, in this minireview, we systematically summarize the recent progress of superstructure in SIBs, assisting in understanding the underlying mechanism of anionic redox that is coupled with transition metal migration, O-O dimer formation, and consequently, the voltage hysteresis. We start with the structure-relationship between anionic redox and superstructures (mainly honeycomb, ribbon and mesh superstructures) by delving into the band structure of these Na-based cathodes. The different properties of the three main superstructures are then compared and discussed, followed by a revisit of recent progress on varying the honeycomb superstructures. Finally, we present our perspectives on how to utilize such superstructure-related anionic redox via stabilizing and tuning the structural units with various strategies. We hope this minireview can clarify the various characteristics of different superstructures and offer a unique insight toward high-energy-density sodium-ion batteries with anionic redox.

The precise incorporation of monomers into polymer chains to create sequence-controlled polymers remains one of the key challenges in modern polymer chemistry. Notably, the alternating, periodic, or block copolymers consisting of two monomers represent the simplest form of sequence-controlled block copolymers. One attractive strategy in preparing sequence-controlled block copolymers is to link two different polymerization cycles, which involves ring-opening polymerization (ROP) and ring-opening copolymerization (ROCOP) due to the large library of cyclic monomers and comonomers. In this work, we report for the first time that switchable polymerization from propylene oxide (PO) and p-tosyl isocyanate (TSI) mixtures in solution using intramolecular phosphonium borane Lewis pair (PBB-Br) as a catalyst. This system can efficiently toggle between the ROCOP of PO/TSI and ROP of PO under mild conditions, enabling the one-pot synthesis of multiblock copolymers with up to 33 segments through nine sequential monomer mixture additions. Physical properties of the copolymers are analyzed, and DFT calculations reveal that biased activation of TSI provides a pathway to mediate the ROCOP of TSI and PO over the ROP of PO. This approach shows strong potential for synthesizing sequentially and architecturally complex polymers with precise monomer sequence control, enabling advanced material design.

Optimizing the active layer morphology by introducing a third component is an effective strategy to enhance the performance of organic solar cells (OSCs). Using dithieno[3,2-a:2″,3″-c]phenazine as the core, a nonfused-ring small molecule (PTBT-SC10) with a large difference in miscibility with the donor and acceptor was obtained by side chain engineering and alteration of the π-bridge. PTBT-SC10 forms a good complementary absorption with the host donor and acceptor, and it has a cascade energy level arrangement with energy levels of the host materials. Grazing incidence wide angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) measurements showed that the addition of only 5% mass fraction of PTBT-SC10 resulted in an optimized vertical phase separation morphology for the binary blend. As a result, the optimized PM6:BTP-eC9:PTBT-SC10 ternary OSCs obtained a power conversion efficiency (PCE) of 19.1%, while the PCE based on the PM6:BTP-eC9 binary OSCs was only 17.7%. This study shows that the vertical phase separation structure of the binary active layer can be precisely tuned by adding only a small amount of the third component when the miscibility of the third component differs significantly from that of the host material. This provides a new strategy to minimize the generation of defect states in the ternary active layer and improve the photovoltaic performance of the device.

An N-heterocyclic carbene (NHC)-catalyzed [3+3] cycloaddition reaction is developed for the enantio- and diastereoselective synthesis of tricyclic pyrimidine rings bearing contiguous C–N and C–C stereogenic axes. The chiral products were obtained in moderate yields and excellent enantio- and diastereoselectivities. Notably, these functionalized molecules exhibit significant potential applications in organic synthesis and bactericide development.

The nucleophile can be oxidized by electrophilic intermediates generated on electrocatalysts under the oxidation potential, and nucleophile oxidation reaction (NOR) has attracted extensive attention in the fields of coupling hydrogen production and organic electrosynthesis. Given that NOR involves electrocatalysis and organic chemistry, the development of this cross-disciplinary field requires a close multi-disciplinary collaboration. Although numerous studies about NOR have sprung up, researchers cannot agree on the NOR mechanism, let alone on utilizing the NOR mechanism. Hence, critically reviewing past works is crucial to establishing a unified conclusion for the NOR mechanism. This review concludes the current progress of NOR and proposes a unified NOR mechanism, which offers guidance and inspiration to subsequent studies of NOR. Firstly, we summarize the adjustable NOR systems, including multiple high-efficiency NOR electrocatalysts and numerous substrate/product systems. Secondly, we discuss the NOR mechanism involving an electrochemical step and a spontaneous non-electrochemical process, and propose the connection between the non-electrochemical process and the nucleophile oxidation pathway. Thirdly, we highlight the design principle of highly effective NOR electrocatalysts based on the NOR mechanism. Finally, several critical issues for the future development of NOR are presented.