Highly flexible cellulose-silica composite aerogels from hemp straw

With the accelerating pace of industrialization, the development of green and low-carbon thermal insulation materials is of great significance for achieving efficient energy utilization and sustainable development. In this study, micrometer-scale cellulose was successfully extracted from agricultural waste hemp straw cores through an alkali treatment and bleaching process. It was then innovatively combined with chitosan, methyltrimethoxysilane (MTMS), and tetraethyl orthosilicate (TEOS) to successfully prepare a flexible cellulose-silica composite aerogel via freeze-drying. Compared with traditional silica aerogels, this material effectively mitigates their typical brittleness and rigidity, with no dusting or fragmentation observed in practical testing when the TEOS content was ≤ 3 wt%. The material exhibited ultra-low density (0.01145–0.01418 g·cm⁻³), enhanced compressibility (75 % height retention after 100 compression cycles under 80 % strain), and excellent thermal insulation performance (a minimum thermal conductivity of 0.046 W·m−1·K−1). The results indicate that chemical cross-linking interactions between the three-dimensional cellulose network and the silica skeleton is the key mechanism underlying the synergistic enhancement of these properties. These findings highlight the potential of biomass-derived aerogels as sustainable alternatives for industrial applications.