Metal-organic framework as luminescence turn-on sensor for selective detection of metal ions: Absorbance caused enhancement mechanism

The luminescence turn-on sensors are more suitable for the practical applications, because they can effectively avoid the wrong response and have a higher signal-to-noise in dark background, compared to the luminescent quenching probes. In this work, we use IRMOF-3 as a luminescent probe to systematically investigate its sensing behavior for detecting metal ions. By examining the relationship of absorbance and luminescent intensity of IRMOF-3 before and after adding metal ions, we propose a novel luminescence turn-on mechanism, i.e., absorbance caused enhancement (ACE) mechanism, to reveal the luminescence turn-on phenomena of IRMOF-3 for selectively sensing M3+ (Cr3+, Al3+, Ga3+, In3+) metal ions. By exploring the effects of M3+ ion concentrations on absorbance and luminescent intensity, we further confirm the ACE mechanism responsible for luminescence turn-on phenomena. The subsequent experimental results indicate that IRMOF-3 exhibits not only high sensitivity and anti-interference ability against M2+ and M+ metal ions, but also have excellent reusability and stability. In short, the ACE mechanism provides a possible strategy for designing luminescence turn-on probes.