Engineering high-performance chrome-free colored leather is currently a tough challenge in the leather industry. Herein, we report on a novel tanning−dyeing integration strategy based on converting natural cochineal carmine (Car) into an effective tanning agent (DCar) without losing its dyeing capabilities via periodate oxidation. Initially, DCar was used as a tanning−dyeing agent, leading to tanned-dyed leather with well-dispersed and fixed collagen fibers (CFs) and a shrinkage temperature (T s ) of ca. 70 °C. Subsequently, this leather was filled and fatliquored to be prepared for the subsequent aluminum fixation of the CFs matrix, which was facilitated by the excellent metal complexation capabilities of DCar. This dual integrative process resulted in successful simultaneous leather tanning and dyeing. Consequently, the resultant crust leather had a T s of ca. 80 °C with an outstandingly dispersed and fixed CFs network and excellent softness, fullness, and commercializable mechanical strength (tensile strength: 13 N/mm 2 ; tear strength: 54 N/mm). Besides, it also had a highly marketable brown color, a smooth grain surface, and excellent coloring uniformity and fastness. These results open the door for a new paradigm, i.e., providing natural pigments and dyes with tanning properties to develop novel and benign dual tanning− dyeing agents for the leather industry.

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High-performance chrome-free leather production is currently one of the most concerning needs to warrant the sustainable development of the leather industry due to the serious chrome pollution. Driven by these research challenges, this work explores using biobased polymeric dyes (BPDs) based on dialdehyde starch and reactive small-molecule dye (reactive red 180, RD-180) as novel dyeing agents for leather tanned using a chrome-free, biomass-derived aldehyde tanning agent (BAT). FTIR, 1H NMR, XPS, and UV-visible spectrometry analyses indicated that a Schiff base structure was generated between the aldehyde group of dialdehyde starch (DST) and the amino group of RD-180, resulting in the successful load of RD-180 on DST to produce BPD. The BPD could first penetrate the BAT-tanned leather efficiently and then be deposited on the leather matrix, thus exhibiting a high uptake ratio. Compared with the crust leathers prepared using a conventional anionic dye (CAD), dyeing, and RD-180 dyeing, the BPD-dyed crust leather not only had better coloring uniformity and fastness but it also showed a higher tensile strength, elongation at break, and fullness. These data suggest that BPD has the potential to be used as a novel sustainable polymeric dye for the high-performance dyeing of organically tanned chrome-free leather, which is paramount to ensuring and promoting the sustainable development of the leather industry.