Ln(3+) post-functionalized metal-organic frameworks for color tunable emission and highly sensitive sensing of toxic anions and small molecules

A facile strategy was put forward to fabricate highly luminescent metal-organic frameworks (MOFs) with tunable and white-light emission by incorporating lanthanide cations (Ln(3+)) into the channels of MIL-121 (Al(OH)(H(2)btec)center dot H2O) whose uncoordinated carboxyl groups can act as post-synthetic modification sites. The intense luminescence of Ln(3+) doped MIL-121 indicates that the framework with rigid, permanently porous structure and non-coordinated carboxyl can serve as both a scaffold and an antenna for hosting and sensitizing the luminescence of Ln(3+) cations. Moreover, a fine-tuning of the emitted color luminescence can be easily achieved by simply modulating the doping ratio or adjusting the excitation wavelength. Notably, the red-green-blue-based white light emitting Ln-MOFs can be realized by simultaneously doping Eu3+ and Tb3+ into the host framework. In addition, because of the excellent luminescence and the structural stability of Ln(3+) functionalized MIL-121 (Ln(3+)@MIL-121) in water or solvents, the Eu3+@MIL-121 was developed as a luminescent probe for sensing of anions in aqueous solutions and small organic molecules. Luminescent studies reveal that Eu3+@MIL-121 not only display a high-sensitivity sensing function with respect to fluoride and dichromate ions but also exhibit significant solvent-dependent luminescent response to small-molecule pollutants, such as chloroform and acetone.