<p>It is of urgent significance to develop highly stable and efficient CrO₄²⁻ detection technology in the fields of drinking water distribution and sewage treatment. A highly stable europium metal-organic framework (Eu-MOF) was designed as fluorescent probe for the efficient detection of trace CrO₄²⁻ in water solutions. This was achieved through the self-assembly of the lanthanide Eu³⁺ and a rigid conjugated organic ligand [2,2’- biquinoline]-4,4’-dicarboxylic acid (H₂L) under hydrothermal conditions. The obtained Eu-MOF exhibits excellent water stability, thermal stability and photostability. The Eu-MOF can quantitatively detect trace amounts of CrO₄²⁻ through fluorescence quenching effect. Its detection sensitivity is 4.48 × 10⁴M^− 1, with a detection limit as low as 0.06 µM (9.7&#xa0;µg/L). This is one of the lowest values for the detection limit of CrO₄²⁻ in aqueous solution and is far below the allowable level for drinking water specified by World Health Organization. The Eu-MOF sensor also demonstrates excellent selectivity, anti-interference ability, repeatability (after 4 cycles), reproducibility and practical feasibility. Furthermore, the fluorescent luminescence and senseing mechanism were studied in detail. The fluorescence senseing mechanism of the Eu-MOF for CrO₄²⁻ detection involves the competitive absorption of excitation energy. The fluorescence-based sensing technology using the Eu-MOF provides a reference for environmental pollution detection and holds potential practical value.</p>