Temporospatial confinement for fabricating MIL-100-templated ultra-small carbon-dots arrays for the abatement of micropollutants

Designing catalysts that synergistically integrate adsorption and heterogeneous photo-Fenton degradation for micropollutant removal remains a significant challenge. Herein, we report a strategy for constructing a series of MOF-based composites with varying carbon dots (CDs) loadings (xCDs@MIL-100(Fe), where x = 0.5, 10, 50, and 100 mM). The CDs arrays were fabricated via low-temperature calcination of glucose confined within the MIL-100(Fe) template. The size and interparticle spacing of the confined CDs could be precisely tuned within the range of 1.15–2.32 nm by varying the MOF template. The resulting composites exhibit enhanced visible-light utilization (bandgap reduced from 3.00 to 2.63 eV) and suppressed charge-carrier recombination, thereby reinforcing the ligand-to-metal charge transfer (LMCT) mechanism, as proved using UV–vis DRS, Mott–Schottky and PL analyses. Among the series, the optimal 50CDs@MIL-100(Fe) composite achieves a substantially improved photocurrent response of 10.79 × 10⁻² μA/cm² and promotes the generation of photogenerated holes and hydroxyl radicals (1.50 × 10⁻⁵ M). Electron paramagnetic resonance (EPR) analysis identified •OH, O₂^•−, and ¹O₂ as the predominant reactive species. A plausible reaction pathway is proposed. The catalyst/PTFE membrane exhibits good stability (Fe leaching <8 μg/L) and reusability, providing a strategy for the rational design of functional materials.