Surface-Modified Dysprosium-Trimesic Acid Metal-Organic Frameworks for the Fluorescent Detection of Coumaphos.

Abstract

We report a novel Dy-BTC metal-organic framework (DTM) platform and its surface-engineered derivatives for highly sensitive, label-free photoluminescent detection of the organophosphate (Op) pesticide coumaphos (CP) in ethanol. Systematic control of synthesis parameters produced a highly crystalline, intensely luminescent DTM scaffold (M/L = 2:1; solvothermal, 120°C; pH 7; EtOH; 24 h), which exhibited selective PL quenching by CP across 0.25-250 ppb. Targeted surface functionalization of DTM with L-ascorbic acid (L-AA) and 11-mercaptoundecanoic acid (MUDA) introduced -COOH and -SH recognition motifs that markedly enhanced analyte affinity and quenching efficiency via noncovalent interactions and electron/energy transfer. The Stern-Volmer constants increased from (1 × 1010) L·mol-1 (DTM) to (4 × 1010) L·mol-1 (DT-AA) and (3 × 1010) L·mol-1 (DT-MUDA), while limits of detection improved from 30.40 ppb (DTM) to 4.89 ppb (DT-AA) and 3.65 ppb (DT-MUDA). The sensing of CP at single-digit ppb levels with good linearity (R2 > 0.96) and low material cost highlights the potential of combining MOF building-unit design with post-synthetic surface engineering. The DT-AA and DT-MUDA platforms therefore provide promising proof-of-concept candidates for subsequent matrix validation and development of portable CP screening approaches for environmental and food-related applications.

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