Hyper-Cross-Linked Polymers-Derived Porous Tubular Carbon Nanofibers@TiO2 toward a Wide-Band and Lightweight Microwave Absorbent at a Low Loading Content

Nanofibrous Porous Organic Polymers and Their Derivatives: From Synthesis to Applications

Engineering porous organic polymers (POPs) into 1D morphology holds significant promise for diverse applications due to their exceptional processability and increased surface contact for enhanced interactions with guest molecules. This article reviews the latest developments in nanofibrous POPs and their derivatives, encompassing porous organic polymer nanofibers, their composites, and POPs-derived carbon nanofibers. The review delves into the design and fabrication strategies, elucidates the formation mechanisms, explores their functional attributes, and highlights promising applications. The first section systematically outlines two primary fabrication approaches of nanofibrous POPs, i.e., direct bulk synthesis and electrospinning technology. Both routes are discussed and compared in terms of template utilization and post-treatments. Next, performance of nanofibrous POPs and their derivatives are reviewed for applications including water treatment, water/oil separation, gas adsorption, energy storage, heterogeneous catalysis, microwave absorption, and biomedical systems. Finally, highlighting existent challenges and offering future prospects of nanofibrous POPs and their derivatives are concluded.

Enhancement of microwave absorption performance of porous carbon induced by Ce (CO3) OH

In recent years, electromagnetic pollution has become more and more serious, resulting in a very negative impact on people's health. Therefore, it is important to develop efficient microwave absorbers to reduce electromagnetic pollution. Here, we construct a novel absorbing material of the polymer gel-derived porous carbon decorated by rare earth compounds (Ce (CO₃) OH). When the thickness is 2.2 mm, the composite exhibits excellent microwave absorption performance with the optimal RL_min value and EAB reached up to -47.67 dB and 5.52 GHz, respectively, covering the Ku band. The high-efficiency microwave absorption is mainly attributed to the synergistic effect of dipole polarization, defect polarization and interfacial polarization. This work not only provides a new view for designing superior absorber materials, but also lay a foundation for their real applications.

Lightweight electromagnetic wave absorbent composites with Fe3O4 nanocrystals uniformly decorated on the surface of carbon spheres

The application of electromagnetic waves has reached every aspect of human life, but the search for superior electromagnetic wave absorbent materials has been a constant quest of researchers. The application of heterogeneous structures has been favored by researchers of electromagnetic wave absorbent materials and the quest for simple preparation methods and homogeneous distribution of heterogeneous structures is continuing. In this study, we synthesized carbon sphere/Fe₃O₄ nanocrystal (CS/Fe₃O₄) composites by uniformly decorating Fe₃O₄ nanoparticles on the surface of carbon spheres through a simple strategy of expanding the heterogeneous structured interface. The heterogeneous interface formed by graphite and amorphous carbon in the carbon spheres is a boundary-type defect and combined with the magnetic loss capability of the Fe₃O₄ nanocrystals, this composite material has excellent electromagnetic wave absorption properties. The composite material synthesized with 0.05 M solution of iron nitrate has the best electromagnetic wave absorption performance of all samples due to the synergistic effect of interfacial polarization, eddy current loss, defect engineering, and magnetic energy attenuation capability. Reflection losses of -50.932 dB and -49.143 dB were achieved at 4.65 GHz and 10.6 GHz respectively, corresponding to thicknesses of 3.74 mm and 1.74 mm. In addition, the widest effective absorption bandwidth (EAB) at 1.27 mm was 4.5 GHz (13.50-18 GHz). This study enhances the electromagnetic wave absorption performance of carbon spheres by surface-decorating Fe₃O₄ nanoparticles, solves the problem of homogeneity of decorative magnetic oxides on the surface of carbon-based materials, and provides new ideas for the design of controllable, lightweight, ultra-thin composites of carbon-based electromagnetic wave absorbent materials that possess strong electromagnetic wave absorption capability.

Dimensional Design and Core-Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption

Electromagnetic (EM) wave absorption materials possess exceptionally high EM energy loss efficiency. With vigorous developments in nanotechnology, such materials have exhibited numerous advanced EM functions, including radiation prevention and antiradar stealth. To achieve improved EM performance and multifunctionality, the elaborate control of microstructures has become an attractive research direction. By designing them as core-shell structures with different dimensions, the combined effects, such as interfacial polarization, conduction networks, magnetic coupling, and magnetic-dielectric synergy, can significantly enhance the EM wave absorption performance. Herein, the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed. The derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized. Moreover, the investigation of the cutting-edge mechanisms is given particular attention. Additional applications, such as oxidation resistance and self-cleaning functions, are also introduced. Finally, insight into what may be expected from this rapidly expanding field and future challenges are presented.

Preparation of core-shell C@TiO2 composite microspheres with wrinkled morphology and its microwave absorption

In this work, we successfully synthesize the core-shell structure carbon@titanium dioxide (C@TiO₂) composite microspheres with wrinkled surface through a three-step method and build up the relationship between the TiO₂ layer thickness and the microwave absorption property. The absorbing mechanism of the novel microsphere is revealed. Interface polymerization is applied for preparation of wrinkled poly glycidyl methacrylate/divinylbenzene polymer microspheres (PGMA/PDVB); Then, TiO₂ layer is controllably coated on the surface of PGMA/PDVB microspheres by hydrolysis of tetrabutyl titanate (TBT); C@TiO₂ composite microspheres are obtained by vacuum carbonization with PGMA/PDVB@TiO₂ microspheres as the precursor. TiO₂ layer thickness on the surface of C@TiO₂ composite microspheres can be effectively adjusted by controlling the amount of TBT. When the amount of TBT is 0.75 mL, C@TiO₂ composite microspheres exhibit the outstanding electromagnetic loss performance. The maximum reflection loss value (RLmax) reaches -49.21 dB at the thickness of 2 mm, corresponding effective absorption bandwidth is 5.27 GHz. The maximum effective absorption bandwidth is 5.5 GHz at 2.2 mm. The results show that the introduction of TiO₂ can regulate electromagnetic parameters and enhance interface polarization ability. Meanwhile, the surface wrinkle structure offers more opportunities for multiple reflections of electromagnetic and introduces a large number of defective skeleton structure. The synergy of multiple advantages makes the absorbing performance of C@TiO₂ composite microspheres significantly improved. This work plays a guiding role for the composition and the structure optimization of existing microwave absorbers.

Applications of porous frameworks in solid-phase microextraction

Porous frameworks are a term of attracting solid materials assembled by interconnection of molecules and ions. These trendy materials due to high chemical and thermal stability, well-defined pore size and structure, and high effective surface area gained attention to employ as extraction phase in sample pretreatment methods before analytical analysis. Solid-phase microextraction is an important subclass of sample preparation technique that up to now different configurations of this method have been introduced to get adaptable with different environments and analytical instruments. In this review, theoretical aspect and different modes of solid-phase microextraction method are investigated. Different classes of porous frameworks and their applications as extraction phase in the proposed microextraction method are evaluated. Types and features of supporting substrates and coating procedures of porous frameworks on them are reviewed. At the end, the prospective and the challenges ahead in this field are discussed.