Upcycling commodity thermosetting polymers into high-quality, high-performance, and high-value materials is a significant solution to severe their environmental pollution and resource waste. However, currently, recycling methods are economically unattractive and/or constitute downcycling, and the recycled products are usually applicable in a single scenario. Herein, a defect engineering strategy is reported for upcycling commodity thermosetting polymers to multifunctional carbon sponges. The three-dimensional interconnected networks, defect structures, and light weights endow these waste melamine-formaldehyde-derived carbon sponges (CMSs) with integrated multiple functionality for use in electromagnetic wave absorption, conversion, and radar- infrared compatible stealth. Specifically, CMS-5 delivers an ultra-strong reflection loss of-67.6 dB and a wide effective absorption bandwidth of 5.84 GHz at 2.18 mm with an ultralow filler loading of 5 wt%. Meanwhile, a high simulated radar cross-section reduction value of 47.17 dB m2 2 and a low thermal conductivity of 28.4 mW m- 1 K- 1 are presented. Furthermore, an integrated electromagnetic-thermal-electrical device is constructed, which reveals a maximum output power of 0.695 mu W during irradiation with electromagnetic waves for 16 s. This work provides a novel and scalable pathway for upcycling waste thermosetting polymers.
