One-Step Synthesis of Closed-Loop Recyclable and Thermally Superinsulating Polyhexahydrotriazine Aerogels

Organic aerogels are an advanced class of materials renowned for their ultralow thermal conductivity and highly porous architecture, making them ideal for applications in thermal insulation, catalysis, and chemical absorption. However, these polymeric networks pose environmental concerns as their permanently crosslinked scaffold makes recycling back to the original monomers virtually impossible. To tackle this issue and develop next-generation organic aerogel, a set of polyhexahydrotriazine (PHT) aerogels specifically designed for closed-loop chemical recycling are prepared. Remarkably, these innovative materials can selectively be synthesized in a one-step condensation reaction using commercially available aromatic amines. They showcase outstanding thermally insulating performance, along with strong mechanical performance, pronounced thermal stability, and intrinsic hydrophobicity, all achieved without the need for additional modifications. More importantly, these aerogels exhibit quantitative depolymerization under acidic aqueous conditions, achieving high yields and purities of the recovered monomers. The successful preparation of fresh organic aerogels from recycled monomers with nearly identical material properties underscores the efficiency and reliability of this recycling process. The facile one-step synthesis process, combined with the high-performance properties and excellent recyclability of these PHT aerogels, accelerates the advancement of sustainable thermally superinsulating materials.