Electronic modulation of Cu1-O4 single-sites in hollow Cu@Y zeolite for ultra-deep and aromatic-resistant adsorptive desulfurization

Copper-based sorbents for adsorption desulfurization have attracted significant interest owing to their potential for high sulfur adsorption capacities. However, their practical application has been severely impeded by the ambiguous active-site structures and, more critically, a drastic loss of capacity in the presence of competing aromatic compounds. This performance bottleneck stems from the lack of electronic specificity in conventional Cu sites to differentiate thiophene from benzene, which leads to unselective adsorption. Herein, we address these challenges by constructing a well-defined single-atom sorbent through a one-pot seeding strategy that precisely anchors Cu 1 O pairs in the supercages of hollow Y zeolite, forming a stable Cu 1 -O 4 -Al 2 bridging configuration. Desulfurization experiments performed using pure benzene as the solvent show that the hollow Cu@Y zeolite achieved a record-breaking sulfur breakthrough capacity of 0.99 mmol/g with 12-fold improvement over conventional Cu Y zeolite, representing state-of-the-art performance among reported copper-based sorbents even under such strongly competitive conditions. After five regeneration cycles, the sorbent still maintained a high adsorption capacity. This Cu 1 -O 4 -Al 2 structure induces a tailored electronic environment where the Cu center becomes highly electron-deficient due to significant charge transfer (1.71|e|) to framework oxygen atoms. As a result, the Cu 1 -O 4 site strongly adsorbs thiophene (−106.8 kJ/mol) via σ-coordination in an η 1 (C) mode (Cu C distance: 2.17 Å), further stabilized by a secondary interaction between the sulfur atom and a framework oxygen (S O distance: 3.02 Å), resulting in a unique “bidentate anchoring” adsorption configuration. Crucially, the highly electron-deficient nature of the Cu centers prevents effective π-complexation with benzene due to insufficient back-donation capability, thereby suppressing competitive aromatic adsorption through electronic repulsion. In situ Fourier transform infrared (FT-IR) spectroscopy directly captured the unique vibrational fingerprint of thiophene undergoing σ-coordination at the Cu 1 -O 4 sites, alongside evidence of the promotion of oligomerization and C 4 species formation. This work not only deciphers the nature of high-performance Cu sites but also establishes an electronic-structure-centered design principle for sorbents targeting deep desulfurization in aromatic-rich environments.