Water-Induced Self-Assembly and In Situ Mineralization within Plant Phenolic Glycol-Gel toward Ultrastrong and Multifunctional Thermal Insulating Aerogels

Biopolymer/silica nanocomposite aerogels are highly attractive as thermally insulating materials for prevailing energy-saving engineering but are usually plagued by their lack of mechanical strength and environmental stability. Lignin is an appealing plant phenolic biopolymer due to its natural abundance, high stiffness, water repellency, and thermostability. However, integrating lignin and silica into high-performance 3D hybrid aerogels remains a substantial challenge due to the unstable co-sol process. In diatoms, the silicic acid stabilization prior to the condensation reaction is enhanced by the intervention of biomolecules in noncovalent interactions. Inspired by this mechanism, we herein rationally design an ultrastrong silica-mineralized lignin nanocomposite aerogel (LigSi) with an adjustable multilevel micro/nanostructure and arbitrary machinability through an unusual water-induced self-assembly and in situ mineralization based on ethylene glycol-stabilized lignin/siloxane colloid. The optimized LigSi exhibits an ultrahigh stiffness (a specific modulus of ∼376.3 kN m kg-1) and can support over 5000 times its own weight without obvious deformation. Moreover, the aerogel demonstrates a combination of outstanding properties, including superior and humidity-tolerant thermal insulation (maintained at ∼0.04 W m-1 K-1 under a relative humidity of 33-94%), excellent fire resistance withstanding an ∼1200 °C flame without disintegration, low near-infrared absorption (∼9%), and intrinsic self-cleaning/superhydrophobic performance (158° WCA). These advanced properties make it an ideal thermally insulating material for diversified applications in harsh environments. As a proof of concept, a dual-mode LigSi thermal device was designed to demonstrate the application prospect of combining passive heat-trapping and active heating in the building.