Fluorescent metal-organic frameworks MIL-101(Al)-NH2 for rapid and sensitive detection of ellagic acid

Ellagic acid (EA) is a symmetric natural phenol bioactive compound present in fruits and nuts, and has attracted substantial interest worldwide owing to its beneficial health effects. Here, the exploration of luminescent metal-organic frameworks (MOFs) of MIL-101(Al)-NH2 (MIL = Materials of Institute Lavoisier) for rapid and sensitive sensing of EA in aqueous solution was reported initially. The porous MIL-101(Al)-NH2 MOFs was synthesized by solvent-thermal method with inexpensive 2-aminoterephthalic acid and aluminum salt, which exhibited uniform spherical crystals (~340 nm) and specific mesoporous structure (3.2 nm). The fluorescence intensity of MIL-101(Al)-NH2 at 425 nm showed a good linear relationship with EA concentration in the range of 0.15–100 μM. The detection limit was as low as 43.8 nM, the rapid response time was within 2 min, and the cost of detection was low. In addition, the "turn off" fluorescence probe could be utilized for visual detection of EA according to the color change under the UV lamp. Based on the Stern-Volmer equation, the quenching constants was decreased with the rise of temperature, which indicated that the probable quenching mechanism was static quenching. The nanoprobe was successfully used to detect EA in the cherry and serum samples. MIL-101(Al)-NH2 represents the first instance of MOFs-based fluorescent probe in EA detection. This work not only enriches the detection method of EA, but also expands the potential application of MIL MOFs in small molecules.