Cr(III) Coordination Complexes with Collagen‐Mimetic Ligands as Alternative Tanning Agents for Sustainable Leather Production

Abstract Chromium tanning process remains the most predominant method for leather production due to its high efficiency; however, it suffers from low chromium fixation and significant environmental impact from chromium‐containing aqueous waste. This study introduces a novel approach combining coordination chemistry and sustainable processing by employing Cr(III) coordination complexes designed with collagen mimetic ligands as alternative tanning agents to enhance chromium‐collagen interactions. Decreasing with this highly concentrated effluent method with Cr(III). Three Cr(III) complexes were synthesized with yields between 76%–85% and characterized by FTIR, ultraviolet‐visible (UV–vis), EPR spectroscopy, and molar conductivity to confirm their octahedral coordination environments. One complex, in particular, exhibited superior interaction with collagen fibers, producing leather with enhanced color uniformity (color SD < 1.5 units, CIE Lab*) and reduced shrinkage (4.5%) compared to the other complexes. Furthermore, it is important to note that chromium concentrations in the tanning effluent decreased by 1.7 ppm, markedly lower than the typical of conventional tanning (>200 ppm). These findings highlight the critical role of ligand design in developing functional coordination complexes for more efficient and environmentally responsible leather tanning.