Green synthesis of hierarchically porous carbons with tunable dielectric response for microwave absorption

The optimization of microwave absorption is closely bound up with the of controllable strucuture of absorber materials. Hierarchically porous carbon (HPC) with two level pore structure has thriving as promising candidates for high performance microwave absorption application. However, fabricating HPC with tunable porous structure in a facile and sustainable manner with high yield is still a challenge for vast use in efficient electromagnetic (EM) wave absorption systems. Herein, a series of hierarchical porous carbon materials with different pore structures were synthesized from wheat flour dough through a facile biomass fermentation method. By gradually increasing the fermentation time, the conchoidal cavities gradually evolved to microscale macropore channels, and the number and size of pore increased synchronously. Microwave absorption studies revealed that the formation of macropore channels led to an apparent enhancement of dielectric properties, which can be further increased with the porosity increasing. Consequently, a strong absorption intensity of −52.0 dB at 2.50 mm and a broad microwave absorption bandwidth of 4.6 GHz at only 1.55 mm were achieved. Excellent microwave absorption performance can be ascribed to the improvement in dielectric loss. This approach shed the insights on achieving low-cost, green and industrial-scale production of EM absorber from renewable biomass.