DFT-guided engineering of hydroxylated Ti₃C₂Tₓ MXene for efficient arsenic removal and electrochemical monitoring in vietnamese groundwater

Arsenic contamination in Vietnamese groundwater threatens millions, with concentrations frequently exceeding 600 μg/L in the Mekong and Red River Deltas. Herein, we report the rational design of a hydroxyl‑enriched two-dimensional Ti₃C₂(OH)₂ MXene nano-assembly that simultaneously achieves ultrahigh arsenic adsorption and ultrasensitive electrochemical detection. Advanced DFT calculations incorporating implicit (PCM) and explicit (AIMD) solvation reveal that surface −OH groups drive the spontaneous formation of highly ordered, self-assembled bidentate arsenate monolayers through a supramolecular-like recognition motif, delivering the strongest aqueous-phase binding energy (−2.15 eV for As(V)) among all terminations (− O , − F ) via 0.34 e⁻ interfacial charge transfer and a pronounced 0.32 eV work-function shift. These atomically engineered surface nano-assemblies translate into exceptional experimental performance: adsorption capacities of 58.3 mg/g (As(V)) and 41.7 mg/g (As(III)), ultra-fast kinetics (<30 min), wide pH tolerance (4–9), and robust selectivity in complex natural matrices. The same material enables portable electrochemical sensing with a 1.8 μg/L limit of detection and <5 % deviation from ICP-MS across real Vietnamese groundwater samples. A 60-day decentralized household pilot in An Giang province consistently delivered effluent arsenic below 10 μg/L without electricity or chemicals. This work establishes hydroxylated Ti₃C₂Tₓ MXene as a powerful dual-functional 2D nano-assembly platform, bridging molecular-level supramolecular design with field-deployable arsenic mitigation in resource-limited regions. Sulfur-functionalized MOF (S-MOF-SH) demonstrates ultra-high selectivity for Pb(II) capture from contaminated water through HSAB-guided coordination chemistry. The thiol-decorated UiO-66 framework achieves exceptional capacity (487.3 mg/g), remarkable selectivity (α > 150), and excellent regenerability (>91 % after 5 cycles), validated in real industrial wastewater treatment.