MOF@lignocellulosic nanofibril aerogel designed by carboxymethylated nanocellulose bridging for thermal insulation and fire retardancy

Under the global issues of environmental pollution and energy crisis, cellulose nanofiber (CNF)–based aerogels have attracted great attention for energy-efficient building application. For safety concern, metal–organic frameworks (MOFs) could be incorporated to endow aerogels with fire retardancy. However, the aerogels prepared by blending of MOFs with cellulose fibers could not achieve fire resistance, while the in situ growth of MOFs in the system with additional chemicals and even environmental unfriendly processes cause high thermal conductivity of the aerogels. In this work, MIL-53(Al) nanoparticles were incorporated to lignocellulosic nanofibril (LCNF) aerogel by carboxymethylated nanocellulose (CMNC) bridging. Such novel binding technique relied on the nanoscaled size and abundant hydroxyl/carboxyl groups of CMNC fibers. In this case, strong molecular interactions were formed between MIL-53(Al) nanoparticles and cellulose fibers to endow aerogel with fire retardancy by char layer formation and gas suppression. In particular, the incorporated MIL-53(Al) nanoparticles provided abundant micropores and somehow prevented the formation of intramolecular hydrogen bonding among fibers to increase the complexity of pore structures. This endowed the aerogel with a thermal conductivity of 30.6 mW m –1 K –1 , which also displayed excellent thermal insulation ability at 250 °C and − 196 °C. The green fabrication method would provide a novel idea for the design of MOF/cellulose composites to broaden their applications. Graphical Abstract