The highly specific detection and mechanism of Cu-MOF-74 fluorescent probe to amino trimethylene phosphonic acid: Experimental study and theoretical calculation of quantum chemistry

Due to the lack of rapid and efficient detection methods for the determination of trace organic phosphonate concentrations in the natural aqueous system, little is known about their impact on the ecosystem. Amino trimethylene phosphonic acid (ATMP) is an organic phosphonate that has been widely used in many fields. In the present work, the copper-based organic framework material (Cu-MOF-74) for the specific detection of amino trimethylene phosphonic acid (ATMP) in aqueous solution was prepared by hydrothermal synthesis using 2,5-dihydroxyterephthalic acid (DHTP) as raw material and copper nitrate trihydrate as metal source. The synthesized material can be used as a “turn-on” fluorescent sensor for the specific sensing of ATMP, the fluorescence intensity of Cu-MOF-74 can be enhanced 24.2 times by ATMP (90 μΜ), the emission wavelength of the fluorescence emission spectrum of the system was blue-shifted, and the detection limit (LOD) of ATMP was 0.844 μΜ. Moreover, the mechanism of ATMP greatly increasing the fluorescence intensity of Cu-MOF-74 was investigated by experimental and theoretical calculations of quantum chemistry. The experimental results showed that ATMP was involved in the coordination of open metal sites in Cu-MOF-74. Multiwfn wavefunction analysis results demonstrated that the charge transfer from the benzene ring and hydroxyl groups of the ligand to the metal (LMCT) occurred during the electron excitation of Cu-MOF-74, but after adding ATMP, the coordination of ATMP with copper led to the interruption and reduction of the energy transfer and electron transfer from ligand DHTP to Cu2+, and the fluorescence intensity of Cu-MOF-74 was improved. The Cu-MOF-74 fluorescent probe exhibited excellent anti-interference ability, high selectivity, good fluorescence intensity stability in the short term, so it can be used as a reliable fluorescent probe for the highly specific detection of low concentration ATMP, the revealed microscopic mechanism of Cu-MOF-74 fluorescent probe to ATMP from the atomic level can provide a theoretical basis for the research of new fluorescence detectors.