Supramolecular Nonwoven Materials via Thermally Induced Precursor Crystallization of Nanocrystalline Fibers/Belts for Recyclable Air Filters

Functionalmicro-/nanofibrous nonwovens have been widelyused inboth civil and military fields. However, traditional nonwoven materialspreparation methods generally require special equipment and are oftenplagued by high-energy consumption or toxic solvent contamination.Here, a thermally induced precursor crystallization (TIPC) approachis reported for preparing macroscopic free-standing supramolecularnonwoven materials, which stemmed from the self-assembly of cocrystalsof melamine and aromatic carboxylic acids. Green solvents are involvedin the entire preparation process without the use of costly specializedequipment, making this strategy cost-efficient, environmentally benign,and scalable in size and quantity. Distinct nanocrystalline fibers/beltsformed by hydrogen bonds and pi-pi interactions inthus-obtained nonwovens are tightly connected in a 3D network, constructingdiverse porous fabrics with outstanding mechanical flexibility andadvantageous thermal stability. These supramolecular nonwovens displayselective optical transmittance and, remarkably, can be utilized asrecyclable air filters. Taking advantage of the thermally reversibleproperty of supramolecular complexes, a proof-of-concept on the closed-looprecycling of supramolecular nonwovens is realized. This work for assemblingcommon small molecules into structurally complex architectures notonly opens up promising avenues for multifunctional supramolecularmaterials based on synthetically facile procedures but also providesa versatile and cost-effective bottom-up approach to preparing micro-/nanofibrousnonwovens for emergent applications.