RhB-Embedded Zirconium-Naphthalene-Based Metal-Organic Framework Composite as a Luminescent Self-Calibrating Platform for the Selective Detection of Inorganic Ions

A series of dye@MOF composites were synthesized through in situ encapsulation of luminous rhodamine B (RhB) molecules into a blue-emissive zirconium-naphthalene-based metal-organic framework (Zr-MOF). The fabricated RhB@Zr-MOF composites exhibit tunable dual-emissive characteristics due to the process of resonant energy transfer from Zr-MOF to RhB. Notably, one of the RhB@Zr-MOF composites (R@D3) exhibited a weak emission at 420 nm and a strong emission at 607 nm, for which the two emissions possess large distinctions in location and intensity and can be referenced with each other in sensing analytes. By using relative fluorescence intensity instead of their absolute fluorescence intensity as the detection signals, R@D3 served as a built-in self-calibrated platform to selectively detect Fe3+ and Cr2O72- ions in water. Compared with the pristine Zr-MOF, the R@D3 composite shows enhanced sensing selectivity to Fe3+ and higher sensibility to Cr2O72-. This study displays the advantages of combining organic dyes with robust Zr-MOFs in tuning fluorescence and sensing performance.