Highly efficient and selective modification of lignin towards optically designable and multifunctional lignocellulose nanopaper for green light-management applications

Transparent lignocellulose nanopaper (LNP) has been demonstrated to be a promising candidate light-management material for next-generation optical engineering applications. Similar to its role in plant cell walls, lignin serves as a vital functional component in LNP matrices. However, its intrinsic light absorption property renders LNP undesirable for a range of optical management systems. Here, a highly efficient, controllable and ecofriendly lignin modification strategy is developed for modulating the optical performance of LNPs by taking advantage of the beneficial synergistic effect of H2O2 and UV light in selectively eliminating lignin chromophores. The obtained lignin-modified LNP features not only a high visible light transmittance (89%) but also a high haze (90%) and excellent UV-shielding capacity, owing to the well-preserved lignin aromatic skeleton structures after lignin modification. Furthermore, patterning is easily achieved on hot-pressing-induced densified LNPs through a selective lignin modification approach, which endows LNPs with intriguing optical designability. Benefitting from the multifunctionality of lignin components for nanopaper matrices, patterned LNPs demonstrate outstanding water and thermal stability, barrier properties, durability and biodegradability, which are of great significance for practical applications. Furthermore, we demonstrate the great applicability of this optically designable and multifunctional LNP as a light-management material for energy efficient buildings by highlighting its attractive sun- and indoor- light managing effects, effective thermal insulation, as well as superior durability for long-term use. In combination with its efficient, ecofriendly and controllable production, this novel high-performing LNP holds great potential in many other applications that require light-management structural materials, such as optoelectronic and sensing devices.