Evolution of supramolecular structure for bamboo cellulose during successive freeze-thaw-pyrolyzing process

Motivated by "bamboo as a substitute for plastic (BASP)" initiative, replacing plastic products with bamboo attracted worldwide attention. However, the BASP products often suffered from mechanical failure under freeze-thaw process, during which varying cellulose supramolecular structure played a critical role. Herein, the structural evolution of supramolecular for cellulosic models including bamboo fiber, parenchyma and pulps were carefully determined during successive freeze-thaw-pyrolyzing process (-80 °C-1600 °C). It was found that increasing treatment temperature from -80 °C to 280 °C resulted in enhanced molecular movements, therefore causing expansion of spacings between the glucan molecular chains. The co-crystallization behavior between water and cellulose crystals majorly took place on hydrophilic (1-10) and (110) lattice planes below 0 °C. To further fulfil zero waste utilization of bamboo cellulose, the evolution of microcrystalline graphite for these cellulosic models was also evaluated. The results indicated that when increasing the treatment temperature to 1600 °C, the bamboo fiber displayed an ideal microcrystalline graphite structure with its d₀₀₂-spacing higher than 0.38 nm accounting for 86.39 %. TGA analysis disclosed that bamboo pulps were the optimized raw material to produce high valued CH₄ syngas, while bamboo fiber had the highest biochar yield about 15.9 %. The present work provided more comprehensive understandings on bamboo supramolecular structure evolution as well as build a multi-aimed utilization routine for bamboo cellulose.