Biomass fractionation is important for creating biorefineries. Researchers compared two processes, organosolv and ionosolv, to recover lignin from poplar. They found that ionosolv at 135°C had the highest lignin recovery of around 70%. Organosolv produced depolymerized lignins with C-O linkages and G units, while ionosolv produced more thermally stable lignins with C-C linkages and S units. Increasing temperature in ionosolv caused lignin repolymerization. This study highlights the differences between the two processes in lignin recovery and properties, which is crucial for making the most of all parts of biomass.