Lignin, an abundant aromatic biopolymer, is a renewable material for CO2 capture when endowed with basic nitrogen sites. We prepared nitrogen-doped lignin via mild functionalization in a deep eutectic solvent, producing materials with increased basicity and accessible porosity. The chemical structure and site distribution were elucidated by 2D-HSQC NMR, supporting successful functionalization of the lignin framework. Complementary spectroscopic signatures and elemental analysis confirm nitrogen incorporation. Gas-sorption measurements indicate enhanced CO2 affinity at near-ambient conditions, consistent with the introduced basic sites. This work outlines a scalable route from biomass to functional sorbents and provides a chemical basis for performance, motivating further mechanistic and process studies