A Dendritic ‘All-for-One’ Dyeing Platform for Auxiliary-Free, Low-Carbon, Water-Efficient Dyeing of Leather

The dyeing of leather remains highly resource-intensive, requiring large quantities of salts, water, and auxiliaries that result in poor dye fixation, elevated CO 2 emissions, and complex wastewater loads that impede circularity. This study introduces an auxiliary-free, closed-loop processing strategy utilizing PAMAM-G0 dendrimers as a multifunctional molecular platform. The dendritic architecture serves as a universal carrier by employing a trimodal mechanistic pathway: electrostatic bridging for Acid Blue 9, hydrogen-bonding interactions for Madder dye, and lone pair-π interactions that prevent π-π stacking in Safranin O. By disrupting molecular aggregation and electrostatic repulsions through robust noncovalent interactions, the dendrimer ensures superior liquid-phase dispersibility and eliminates the need for traditional leveling agents, mordants, and fixing agents. PAMAM-G0 functions as a carrier, intercalating into the collagen triple helix via hydrogen bonding to facilitate deep-matrix penetration and uniform coloration. This reduces dyeing duration, water consumption, and energy demand by nearly 50%. Crucially, this dendritic medium enables a closed-loop system where the dye bath is directly reused for five subsequent cycles without compromising performance. Quantitative sustainability metrics revealed a carbon avoidance of ∼831 kg CO 2 per ton of substrate and a 50% reduction in effluent chemical oxygen demand (COD). By integrating mechanistic insights with quantified green chemistry indicators, this approach provides a scalable pathway for transitioning leather manufacturing into a low-carbon, circular bioeconomy.