Polymer-based dielectric composites are pivotal for advanced pulsed power and power electronics, yet synergistically enhancing dielectric constant and breakdown strength remains a formidable challenge. Herein, we report a controllable layer-by-layer spray assembly strategy to fabricate ordered multilayer polyetherimide (PEI)-based composites with alternating high-dielectric and high-insulation layers. Homologous carboxylated PEI (CPEI) was designed and covalently grafted onto boron nitride nanosheets (BNNS) and barium strontium titanate (BST) fillers, ensuring exceptional interfacial compatibility. This enabled the precise deposition of CPEI@BNNS/PEI and CPEI@BST/PEI layers, yielding 3-, 5-, and 7-layer films. The 7-layer film achieved a high dielectric constant of 7.43 at 1 kHz, a remarkable breakdown strength of 731.2 kV·mm^-1, and a record discharge energy density of 20.87 J·cm^-3—4.91 times that of pure PEI—while maintaining >90% charge-discharge efficiency. Comprehensive characterization and simulations revealed that the alternating multilayer structure creates deep-level interface traps that effectively suppress space charge migration, homogenize the internal electric field, and block electrical tree propagation. This work provides a facile and scalable pathway for the design and fabrication of high-performance ultrathin dielectric films.

In recent decades, electromagnetic shielding materials have been widely explored due to their promising applications in electronic communication, aerospace, military, and medical equipment. Numerous pioneering works have been reported on MXene/nanocellulose composites, which possess various structures and excellent electromagnetic shielding properties. This article reviews the latest progress of MXene/nanocellulose composites in electromagnetic interface shielding applications, with a particular focus on preparation strategies, toughening mechanisms, and structural design. More importantly, we have reviewed the toughening mechanism of MXene/nanocellulose composites from three aspects: physical toughening mechanism, chemical toughening mechanism, and synergistic toughening mechanism. In addition, we systematically analyzed the current technological limitations and proposed potential research directions to guide future development. This work will greatly advance the rational design and practical application of high-performance MXene/nanocellulose electromagnetic shielding composites.

The advancement of efficient and environmentally sustainable heterogeneous catalysts that facilitate the transformation of carbon dioxide (CO₂) into chemicals has gained considerable attention. In this study, we synthesized a carbon nitride (C₃N₄) functionalized with copper phthalocyanine (CuPc) and ionic liquid (IL) (C₃N₄-CuPc-IL) and employed it as an efficient catalyst enabling the cycloaddition of CO₂ with epoxides. The presence of urea/urethane groups, Cu²⁺ ions, and I⁻ ions that can effectively activate and open the epoxide ring was confirmed by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). Meanwhile, the multiple nitrogen-containing structures (copper phthalocyanine, C₃N₄, and quaternary ammonium cationic structures) facilitated the adsorption and activation of CO₂. Consequently, C₃N₄-CuPc-IL demonstrated high catalytic efficiency for the cycloaddition between CO₂ and epoxides. Specifically, with 5.0 wt.% loading of C₃N₄-CuPc-IL catalyst under 2.0 MPa and 120 °C for 12 h, the yield of cyclic carbonate reached 98%. Additionally, the prepared catalyst demonstrated excellent structural stability and recyclability, alongside high catalytic activity toward various epoxides. Density functional theory (DFT) calculations indicated that the ring-opening reaction represents the rate-determining step in the C₃N₄-CuPc-IL catalyzed cycloaddition reaction, with an energy barrier of only 24.2 kcal/mol. The impressive catalytic performance of C₃N₄-CuPc-IL confirmed the synergistic catalytic effect of hydrogen bond donor groups, Lewis acidic sites, and ionic active sites in the CO₂ cycloaddition reaction, providing theoretical guidance for the design of CO₂ conversion catalysts.