Boron difluoride modified zinc metal–organic framework-based “off–on” fluorescence sensor for tetracycline and Al³⁺ detection

A novel fluorescence “off–on” probe was developed using a boron difluoride–modified zinc metal–organic framework (Zn-MOF3) for sensitive determination of tetracycline (TC) and Al³⁺. The Zn-MOF3 has excellent optical property and good applicability in aqueous phase. The fluorescence recorded at 436 nm was quenched at the excitation wavelength of 336 nm. Signal-off detection of tetracycline via fluorescence quenching of Zn-MOF3 is based on the inner filter effect. Fluorescence on–off-on detection of Al³⁺ occurs via the specific binding between tetracycline and Al³⁺. The limits of detection for TC and Al³⁺ were 28.4 nM and 106.7 nM, respectively. This probe exhibited high selectivity which was used for the determination of TC and Al³⁺ with satisfied recoveries (89.8 to 105.6% for TC, 90.0 to 110.4% for Al³⁺) and good precision (< 5%) in milk. The developed sensor represents the first “off–on” system for fluorescence detection of TC and Al³⁺ based on Zn-MOF3 with a better aspect of the innovation.