Jianyu Cao

A photocatalyst-free, visible-light-driven three-component synthesis of perfluoroalkylated pyrimido[1,2-b]indazoles via an in situ DABCO/perfluoroalkyl iodide EDA complex is developed for accessing nitrogen-fused heterocycles.

The development of chemically robust and synthetically accessible redox‐active organics is paramount for the advancement of sustainable aqueous organic redox flow batteries (AORFBs). While TEMPO derivatives are premier catholyte candidates, their practical utility is frequently hampered by complex, multistep synthesis and the susceptibility of the charged oxoammonium state to irreversible ring‐opening degradation. We novelly provide HOTEMPO‐SO ₃ Na, an anionic TEMPO derivative at high yield and purity, through simple Corey–Chaykovsky epoxidation of readily available triacetonamine followed with ring opening by NaHSO ₃ and H ₂ O ₂ oxidation. The new strategy started from economic raw materials, eliminated halide ion‐exchange protocols, and complex column purification requirement, offering a highly scalable and halide‐free alternative for large‐scale production. In a pH‐neutral AORFB, the system demonstrates outstanding durability with a capacity fade rate of 0.0066% per cycle over 600 cycles in 0.1 M, though it deteriorates much faster in high concentration. This work establishes a scalable framework for engineering high‐performance anionic redoxmers through simplified, atom‐economic epoxidation–sulfonation strategy.

Organic bipolar small molecule materials have emerged as promising candidates for dual-ion batteries owing to their intrinsic capability to reversibly accommodate both anions and cations. However, the rational design of bipolar molecules that combine high capacity, long-term cycling stability, and feasibility for symmetric device configuration remains a significant challenge. This study reports a novel π-conjugated bipolar organic small molecule, N1,N4-di(quinoxalin-2-yl)benzene-1,4-diamine (DQPDA), and evaluates its electrochemical performance. In Li half-cells, DQPDA delivers a high initial discharge capacity of 843 mAh g–1 at 0.1 A g–1 and retains excellent cycling stability over 3000 cycles at 5 A g–1. Furthermore, DQPDA-based symmetric all-organic batteries exhibit a high specific capacity of 156 mAh g–1 at 0.5 A g–1 (based on the mass of the anode active material) and achieve nearly 100% capacity retention after 20,000 cycles at a high current density of 10 A g–1. Mechanistic investigations reveal that the bipolar characteristics arise from the n-type (C=N/C–N) and p-type (–NH–/=NH+–) redox actions within the molecular framework. This work provides a molecular design strategy for developing low-cost and highly sustainable symmetric organic batteries based on bipolar organic materials.

Organic redox-active molecules are promising catholyte materials for aqueous organic redox flow batteries (AORFBs), yet they often suffer from low solubility and poor cycling stability. Herein, we report a series of water-soluble phenothiazine derivatives functionalized with quaternary ammonium groups. The optimized compound, N,N,N-trimethyl-1-(10H-phenothiazin-10-yl) propan-2-aminium chloride (TMiPrPTCl), exhibits exceptional solubility (2.69 M in water) and a high redox potential (0.902 V vs. SHE). A comparative study of four derivatives reveals that side-chain length and branching critically modulate both solubility and degradation pathways: while three-carbon-linked analogs N,N,N-trimethyl-3-(10H-phenothiazin-10-yl)propan-1-aminium chloride (TMPrPTCl) degrade primarily via irreversible oxidation to sulfoxide, two-carbon-linked species (TMiPrPTCl) undergo additional side-chain cleavage, leading to rapid capacity fade. Although the quaternization strategy successfully achieves record solubility, the electrochemical stability remains a key challenge. Post-cycling analysis confirms the loss of redox activity and the formation of inert products. This work highlights the delicate balance between solubility enhancement and molecular stability, providing clear design guidelines for future phenothiazine-based catholytes.

Aqueous redox flow batteries (ARFBs) are a promising solution for large-scale energy storage; however, the development of organic posolytes that combine high redox potential with long-term stability remains a significant hurdle. This study introduces sodium 3-(10H-phenoxazin-10-yl)propane-1-sulfonate (POZS), a novel sulfonate-functionalized phenoxazine derivative designed to overcome these limitations. By incorporating hydrophilic anionic sulfonic groups, this molecular engineering strategy enhances the structural stability of redox-active phenoxazine materials. Although POZS shows limited solubility in pure water, its solubility increases to 0.98 M (equivalent to a charge capacity of 26.3 Ah L⁻¹) upon the addition of 1.5 M tetraethylammonium chloride (TEAC). This enhancement suggests that the supporting electrolyte optimizes the ionic environment and mitigates intermolecular aggregation, thereby facilitating higher active species concentration. Electrochemical characterization of POZS reveals a highly positive redox potential of 1.51 V (vs. Zn/Zn²⁺) and rapid electron transfer kinetics (2.02 × 10⁻² cm s⁻¹). When tested in a zinc-based hybrid flow cell, the POZS posolyte demonstrates excellent rate capability (up to 50 mA cm⁻²) and a temporal capacity fade rate of 0.335% per hour over 500 cycles—a nearly five-fold improvement over previously reported quaternized phenoxazines. Post-cycling analyses indicate that while the phenoxazine core remains susceptible to nucleophilic ring substitution, the pendant sulfonate groups ensure that any resulting byproducts remain soluble, preventing the catastrophic depletion typically caused by the precipitation of degraded active species. These findings establish a robust molecular framework for the design of high-potential, durable organic posolytes for sustainable energy storage systems.

Lithium sulfur batteries (LSBs) are regarded as the potential next-generation energy storage system due to their high theoretical energy density and low cost. However, LSBs also face problems such as the dissolution of lithium polysulfide, volume expansion, and the formation of lithium dendrites. Optimizing the design of sulfur cathode materials to tackle these issues at their source is the primary approach to enhancing the performance of LSBs, since the inherent limitations of sulfur are the root cause of the challenges in LSBs. The review covers the latest research on carbon-based sulfur cathode materials of LSBs, including structural design and functional optimization strategies, aiming to prepare multifunctional carbon-based sulfur cathodes by integrating physical confinement, chemical adsorption, and catalytic effect towards lithium polysulfides. The future development directions are prospected, including material design, optimization of reaction mechanisms, and low-cost preparation technologies.

Using recyclable CdSeS/CdZnSe/ZnSe/ZnS core/shell quantum dots (QDs) as a photocatalyst under visible light irradiation, the synthesis of α-(4-pyridyl)benzylaniline derivatives was achieved through a three-component reaction. These reactions offer advantages such as low catalyst loading, wide substrate scope, high yield, mild reaction conditions, and easy scalability. They have been successfully applied for the derivatization of natural amino acids and pharmaceutical late-stage structural modification. Importantly, this core/shell QD exhibits a remarkably high turnover number (TON) of 2.27 × 10⁵ and can be easily recovered and recycled in the reaction for more than 5 times without significant loss of catalytic activity. Mechanistic studies reveal that thiols/thiophenols in the reaction serve as proton donors, facilitating the reduction of cyanopyridine and the in situ form of imine.