Fluorescent probe for Fe³⁺ detection based on a guest molecular luminescent metal–organic framework

The zinc(II) bis-(8-hydroxyquinoline) (Znq 2 ) has excellent photoluminescence properties, and its fluorescence emission can be significantly quenched by Fe 3+ in water. To accelerate the detection response of Znq 2 to Fe 3+ , a luminescent metal–organic framework Znq 2 @ZIF-8 based on guest molecular luminescence was constructed by growing zeolite imidazolate framework-8 (ZIF-8) on the outer surface of Znq 2 . The results show that the prepared Znq 2 @ZIF-8 has an octahedral core–shell structure, a particle size of approximately 1–3 μm, an enhanced specific surface area of 1105.41 m 2 g −1 , and with a stable green luminescence at 495 nm. A fluorescence analytical method was developed for the detection of Fe 3+ in water, the correlation coefficients were significant in the Fe 3+ concentration range of 0–600 μmol L −1 , and the limit of detection was as low as 3.89 μmol L −1 . The spiked recoveries of tap water samples demonstrated that the method could be applied to practical applications. The mechanism of fluorescence detection is that Fe 3+ participates in the competitive coordination of Znq 2 @ZIF-8 metal centers, leading to the collapse of the crystal structure, meanwhile, Fe 3+ produces a certain degree of competitive absorption of the excitation light of Znq 2 @ZIF-8. This method was applied for the detection of Fe 3+ in water with good selectivity, anti-interference ability, and has the potential to be used as a rapid detection method.