Facilitating the Production of Porous Materials from Lignin

The development of porous materials from lignin presents a promising approach to addressing environmental challenges, particularly in the fields of pollutant adsorption. However, lignins typically exhibit low porosity and limited surface area, restricting their direct applicability. This thesis investigates two distinct strategies for transforming lignin into hierarchically porous materials: the sol–gel process combined with polymerization-induced phase separation (PIPS), and high internal phase emulsion (HIPE) templating.
The first part of this thesis responds to the critical need for sustainable alternatives to conventional heavy metal adsorbents, which are often expensive, derived from non-renewable sources, and potentially toxic. Focusing on lignin as an abundant but underutilized biopolymer, lignin-based xerogels (LBX) were developed through an environmentally friendly and scalable sol–gel/PIPS approach. By systematically varying lignin type, crosslinker, catalyst, and polymeric additives, clear correlations were established between synthesis parameters and material morphology. This work represents the first reported use of PIPS to tailor the structure of lignin-based porous systems, yielding monolithic macroporous xerogels. Unlike most lignin- based adsorbents reported in the literature, the LBX developed in this work were produced without any post-treatment or carbonization, thereby reducing processing costs and preserving the native chemical functionality of lignin. Moreover, their monolithic form eliminates the need for particle recovery or filtration and allows independent control over porosity, connectivity, and permeability, which are key properties for practical wastewater treatment applications.
The second part of this thesis addresses the limitations of conventional molecular surfactants in high internal phase emulsion systems, which often require high concentrations and demonstrate poor long-term stability. While lignin nanoparticles (LNPs) have shown potential as Pickering stabilizers, their unmodified surface chemistry often proves inadequate for demanding emulsion applications. Drawing inspiration from natural lignin–carbohydrate complexes in plant cell walls, a novel approach to generate sustainable Janus LNP-based emulsifiers with balanced amphiphilicity was identified. This research focused on Pickering emulsions stabilized by LNPs, examining the effects of nanoparticle size and lipid phase properties on emulsion stability. The results confirmed the strong stabilizing ability of LNPs, highlighting their potential in future HIPE stabilization for hierarchical porous material synthesis. Finally, chemical modification of LNPs was successfully achieved, establishing a foundation for next-generation bio-based Pickering stabilizers with even greater emulsification efficiencies for the preparation of HIPEs and the generation of lignin-based porous materials.