Defect-steering the prominent thermal conduction, microwave absorption, and electrical insulation of porous g-C3N4 nanofibers

The escalating levels of electromagnetic (EM) pollution and heat accumulation in electronics accentuate the pressing need for developing materials with prominent heat-conducting, microwave-absorbing, and electrical insulating properties. Herein, we pioneered the utilization of porous g-C3N4 nanofibers as a multifunctional filler, which were synthesized by a nitric acid precipitation-annealing route. The annealing temperatures (Ta) was controlled to tune the defect-dependent performance of porous g-C3N4 nanofibers. With Ta elevating from 450 °C to 600 °C, the conductivity (σ) and thermal conductivity (TC) steadily increase and peak at 600 °C (TC = 2.149 W/(m⋅K); σ = 0.00475 S/m). These variations could result from reduced defects, which favor not only the generation and migration of electrons but also the mitigation of phonon-defect scattering. Meanwhile, the low defects can improve their permittivity and attenuation capabilities, attaining optimal microwave absorption properties with a larger absorptive bandwidth (6.4 GHz), higher absorption (−27.56 dB), and a thinner film (2.3 mm). Furthermore, the 1D structure of the porous g-C3N4 nanofibers offers a 3D interconnected continuous path for electron/phonon transfer. These properties distinguish the porous g-C3N4 nanofibers from the majority of other previously reported materials. This study also brings out a straightforward and efficient method for fabricating advanced multifunctional fillers in electronic packaging materials.