Sustainable Upcycling of Office Waste Paper Into Cobalt/Carbon Aerogels for Highly Efficient Microwave Absorption

The global community is increasingly focused on the conversion and utilization of waste materials, yet office waste paper (OWP), one of the most common solid wastes, still lacks an efficient and eco-friendly disposal method. The massive accumulation of OWP not only causes significant resource waste but also imposes severe pollution on the environment. In this study, OWP is selected as the source of carbon aerogels, which are further upgraded to Co/C aerogels (Co/CAs) through the in situ growth and pyrolysis of ZIF-67 crystals. Notably, the heterogeneous attachments derived from ZIF-67 crystals significantly enriched electromagnetic loss mechanisms, thereby reinforcing microwave absorption performance. Specifically, an optimum sample, Co/CA-2, exhibited a porosity of over 80% and achieved an effective absorption bandwidth of 5.6 GHz with a thickness of merely 1.6 mm. Its performance was superior to that of most microwave absorbing materials prepared from waste materials. It is believed that this work not only developed a low-cost and sustainable strategy for preparing high-performance wave-absorbing materials but also provided a brand-new idea and direction for the treatment of OWP.