Superstructured wood-based carbon materials for broadband light absorption and CO2 capture

Light is an abundant resource; however, stray light can significantly impact the performance and longevity of optical systems. Adverse effects such as reduced image contrast and signal degradation highlight the need for advanced solutions to effectively mitigate these challenges. Superblack materials, with near-zero light reflectance, are in high demand to enhance several light-based technologies. In this study, we developed wood-based spectral shielding materials with exceptionally low reflectance across the UV-VIS-NIR (250–2500 nm) and MIR (2.5–15 μm) ranges. Using a straightforward top-down approach, we produced robust superblack materials by removing lignin from wood and carbonizing the delignified wood at 1500 °C. This process induced shrinkage stresses in subwavelength severed wood cells, forming vertically aligned carbon microfiber arrays (~100 μm thick) with light reflectance as low as 0.36 %. We further synthesized multiscale carbon supraparticles (SPs) through a soft-templating process involving lignin nano- and microspheres bound with cellulose nanofibrils (CNFs). Following oxidative thermostabilization, these lignin SPs exhibited high mechanical strength due to their interconnected nanoscale networks. In further work, by inserting lignin particles (LPs) into delignified wood and carbonizing the structure, we created a carbonized reconstituted wood (cRW) system with enhanced dimensional fidelity and finely tuned light-absorbing fibrillar microstructures. They resulted in broadband light traps that achieved superabsorbance, exceeding 99.8% across a wide range of wavelengths, from infrared to ultraviolet. Tiled cRW structures, optically welded for customizable size and shape, demonstrated superior laser beam reflectivity compared to commercial light stoppers, eliminating thermal ghost reflections. This makes them promising candidates as reference infrared radiators for thermal imaging device calibration. Beyond optical applications, the carbon SPs also offer hierarchical adsorption sites, achieving a CO₂ adsorption capacity of 77 mg CO2·g-1. This innovation in the area of carbon capture was shown to solve the diffusion and kinetic limitations of conventional nanoparticle-based systems. Overall, this thesis summarizes wood-derived solutions that go from multispectral shielding to carbon capture technologies.