Cu-N Coordination-Mediated Decoupling of H2S Absorption and Oxidation for Efficient Wet Oxidative Desulfurization

Abstract

Conventional wet oxidative desulfurization suffers from the synchronous absorption-oxidation of H2S, which induces sulfur deposition, viscosity rise, and equipment fouling. Here, we establish a stepwise "coordination capture-air regeneration" paradigm that decouples H 2 S uptake from oxidation. In this system, a Cu2+ -1-MI (1-methylimidazole)/DMF (N,N-Dimethylformamide) solvent selectively anchors H 2 S through Cu-N coordination during absorption, while controlled air exposure regenerates the solvent and precipitates sulfur in a separate stage. The formulation achieves a breakthrough capacity of 14.3 g.L -1 under ambient conditions, maintains ~95% capacity after multiple absorb-regenerate cycles, and shows strong water tolerance. At the optimal Cu 2+ :1-MI ratio of 1:2, the liquid is near-neutral (pH ≈ 7.3) and induces very low corrosion (~10 -3 mm•a -1 ) on 304L/316L stainless steels.Spectroscopy and density functional theory (DFT) calculations reveal that a CuN 4 resting state dynamically rearranges into CuN 2 /CuN 3 reactive states, enabling stable Cu-(1-MI) 2 -2HS complexes; during regeneration, O 2 is activated at these sites to oxidize HS⁻ to elemental sulfur while restoring Cu 2+ centers. This "coordination anchoring-selective regeneration" principle overcomes deposition and corrosion challenges, offering a practical and scalable solution for wellhead and high-pressure natural-gas purification.