Glass‐Blowing‐Inspired Upcycling of Thermosetting Polymer to Neuron‐Like Hierarchical Carbon for Microwave Absorption and Conversion

Abstract Upgrading thermosetting polymer waste and harvesting unwanted electromagnetic energy are of great significance in solving environmental pollution and energy shortage problems. Herein, inspired by the glass‐blowing art, a spontaneous, controllable, and scalable strategy is proposed to prepare hollow carbon materials by inner blowing and outside blocking. Specifically, hierarchically neuron‐like hollow carbon materials (HCMSs) with various sizes are fabricated from melamine‐formaldehyde sponge (MS) waste. Benefiting from the synergistic of the hollow “cell body” and the connected “protrusions” networks, HCMSs reveal superior electromagnetic absorption performance with a strong reflection loss of −54.9 dB, electromagnetic‐heat conversion ability with a high conversion efficiency of 34.4%, and efficient energy storage performance in supercapacitor. Furthermore, a multifunctional device integrating electromagnetic‐heat‐electrical energy conversion is designed, and its feasibility is proved by experiments and theoretical calculations. The integrated device reveals an output voltage of 34.5 mV and a maximum output power of 0.89 µW with electromagnetic radiation for 60 s. This work provides a novel solution to recycle polymer waste, electromagnetic energy, and unwanted thermal energy.