Direct construction of N/S-rich Zn-DMTD-MOGs for ultrafast Pb(II) removal: Synergistic chelating/monodentate coordination and LMCT mechanism

A widely applicable Zn-DMTD-MOGs was prepared via direct construction strategy. • Zn-DMTD-MOGs shows great potential for trace heavy metals removal from real water. • DFT provides a local coordination cluster model for amorphous MOGs at atomic scale. • Synergistic chelating/monodentate coordination and LMCT enable efficient lead capture. Metal-organic gels (MOGs) have attracted extensive attention in the field of heavy metal removal, owing to their advantages including ease of surface modification, good stability, hierarchical pore structure, tunable functional groups, and mild and facile preparation conditions. However, the existing MOGs still leave considerable room for performance improvement. To produce MOGs with enhanced adsorption sites, high specific surface area, and greater pore volume, this study combined ultrasound-assisted nucleation with a high-concentration reaction strategy and triethylamine-mediated deprotonation, thereby enabling direct coordination between 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) and Zn 2+ . Then, Zn-DMTD-MOGs material with higher-density N and S adsorption sites was successfully synthesized. The material exhibits a disordered particle-stacked amorphous structure with abundant mesopores (3–24 nm). Adsorption experiments demonstrate that the material achieves a trace Pb(II) removal efficiency of 96.98% within 10 s. The material achieves wide applicability over a low concentration range (≤ 42 mg/L) and a broad pH range (3.5–10.5), along with favorable stability, good reusability, and applicability to real water matrices. A local coordination cluster model was obtained through density functional theory (DFT) geometry optimization, and a synergistic chelating/monodentate coordination and ligand-to-metal charge transfer (LMCT) mechanism was established. The analysis reveals that the material adsorbs Pb(II) primarily through chelation at dual N/S sites and monodentate coordination at single S sites. This mechanism endows Zn-DMTD-MOGs with ultrafast adsorption kinetics and excellent cyclic stability, making them promising candidates for heavy metal remediation in drinking water sources. Download: Download high-res image (120KB) Download: Download full-size image