Investigation on the metal ion sensing properties of fluorescent IRMOF-3

A luminescent metal-organic framework (IRMOF-3) was prepared by the hydrothermal method, and selective tests were conducted on eight metal ions (Cu2+, Mg2+, Ca2+, Co2+, K+, Al3+, Na+, Zn2+). The results showed that Cu2+ and Co2+ could quench the fluorescence of IRMOF to a large extent. There was good linearity for Cu2+ in the range of 20-100 μM and for Co2+ in the range of 60-100 μM, with detection limits of 6.29 μM and 25 μM respectively. By analyzing the changes in the microstructure and optical properties of IRMOF-3 before and after the addition of metal ions, we believed that Cu2+ or Co2+ may undergo a chelation reaction with the ligands in IRMOF-3. The formed chelates reduce the absorption of the excitation light, which in turn leads to the decrease or quenching of the fluorescence intensity. Moreover, Cu2+ can bond better with the ligands than Co2+, thus exhibiting higher selectivity and sensitivity.