The conductive polymer composites (CPCs) with highly efficient electromagnetic interference (EMI) shielding effectiveness (SE) are always accompanied with excessive reflectivity, which would cause serious secondary EMI pollution. In this regard, the significant reduction of EMI reflection of CPCs to alleviate secondary pollution is deemed to be very important. Herein, a promising cyanate ester (CE) based composite was successfully fabricated by compounding carbonized spent coffee grounds (C-SCG) and graphene nanosheets (GNSs) via a facile solution blending followed by a hot-pressing method. Benefiting from the porous structure of C-SCG and the layered structure of GNSs, a three-dimensional (3D) multi-interface conductive network in the CE was easily constructed. The EMI SE of the resultant 9 wt% C-SCG/CE composite (C9) is 15.38 dB and dramatically enhanced to 31.09 dB with the presence of 3 wt% GNSs. The remarkable enhancement is mainly attributed to the formation of the efficient conductive pathways as well as the well-dispersion of the incorporated fillers. Meanwhile, the absorption-dominated shielding mechanism in the prepared composites gets benefit from the synergistic effect of porous C-SCG and lamellar GNSs, which effectively captures and attenuates electromagnetic waves. These encouraging findings extend the practical applications of porous biocarbon materials in EMI shielding field.

具有高效电磁干扰（EMI）屏蔽效能（SE）的导电聚合物复合材料（CPCs）总是伴随着过度的反射率，这会造成严重的二次EMI污染。在这方面，显着降低 CPC 的 EMI 反射以减轻二次污染被认为是非常重要的。在此，通过将碳化废咖啡渣（C-SCG）和石墨烯纳米片（GNS）通过简单的溶液混合，然后是热压方法。得益于 C-SCG 的多孔结构和 GNS 的层状结构，CE 中的三维 (3D) 多界面导电网络很容易构建。所得 9 wt% C-SCG/CE 复合材料 (C9) 的 EMI SE 为 15.38 dB，并且在 3 wt% GNS 的存在下显着增强至 31.09 dB。显着的增强主要归因于有效导电通路的形成以及掺入的填料的良好分散。同时，制备的复合材料中吸收主导的屏蔽机制受益于多孔 C-SCG 和层状 GNS 的协同效应，可有效捕获和衰减电磁波。