Huang Mengqiu, Wang Lei, Pei Ke, You Wenbin, Yu Xuefeng, Wu Zhengchen, Che Renchao
Laboratory of Advanced Materials, Department of Materials Science and Collaborative Innovation Center of Chemistry for Energy Materials (iChem), Fudan University, Shanghai, 200438, P. R. China.
Small. 2020 Apr;16(14):e2000158. doi: 10.1002/smll.202000158. Epub 2020 Mar 17.
Metal-organic framework (MOF) is highly desirable as a functional material owing to its low density, tunable pore size, and diversity of coordination formation, but limited by the poor dielectric properties. Herein, by controlling the solvent and mole ratio of cobalt/linker, multidimension-controllable MOF-derived nitrogen-doped carbon materials exhibit tunable morphology from sheet-, flower-, cube-, dodecahedron- to octahedron-like. Tunable electromagnetic parameters of Co@N-doped carbon composites (Co@NC) can be obtained and the initial MOF precursor determines the distribution of carbon framework and magnetic cobalt nanoparticles. Carbonized Co@NC composites possess the following advantages: i) controllable dimension and morphology to balance the electromagnetic properties with evenly charged density distribution; ii) magnetic-carbon composites offer plenty of interfacial polarization and strong magnetic coupling network; iii) a MOF-derived dielectric carbon skeleton provides electronic transportation paths and enhances conductive dissipation. Surface-mediated magnetic coupling reflects the stray magnetic flux field, which is corroborated by the off-axis electron holography and micro-magnetic simulation. Optimized octadecahedral Co@NC sample exhibits the best microwave absorption (MA) of -53.0 dB at the thickness of 1.8 mm and broad effective frequency from 11.4 to 17.6 GHz (Ku-band). These results pave the way to fabricate high-performance MA materials with balanced electromagnetic distribution and controlled morphology.
金属有机框架材料（MOF）因其低密度、可调节的孔径以及配位结构的多样性而成为极具吸引力的功能材料，但受限于其较差的介电性能。在此，通过控制溶剂以及钴/连接体的摩尔比，多维可控的MOF衍生氮掺杂碳材料呈现出从片状、花状、立方状、十二面体状到八面体状的可调节形态。可以获得Co@N掺杂碳复合材料（Co@NC）的可调节电磁参数，并且初始的MOF前驱体决定了碳骨架和磁性钴纳米颗粒的分布。碳化后的Co@NC复合材料具有以下优点：i）尺寸和形态可控，以平衡电磁性能并使电荷密度分布均匀；ii）磁性-碳复合材料提供大量的界面极化和强磁耦合网络；iii）MOF衍生的介电碳骨架提供电子传输路径并增强导电耗散。表面介导的磁耦合反映了杂散磁通场，这通过离轴电子全息术和微磁模拟得到了证实。优化后的十八面体Co@NC样品在1.8 mm厚度下表现出最佳的微波吸收（MA），为-53.0 dB，有效频率范围从11.4至17.6 GHz（Ku波段）。这些结果为制备具有平衡电磁分布和可控形态的高性能MA材料铺平了道路。
