Water Stable [Tb4] Cluster-Based Metal-Organic Framework as Sensitive and Recyclable Luminescence Sensor of Quercetin

A novel 3D metal organic framework (MOF)-{[Tb-3(CBA)(2)(HCOO)(mu(3)-OH)(4)(H2O)]center dot 2H(2)O center dot 0.5DMF}(n) (S-1) was synthesized by the solvothermal method. The crystal structure indicates that [Tb4O4] cubane clusters self assemble into an infinite chain by sharing vertex, which is further linked to adjacent chains through 1,1-cyclobutanedicarboxylic acid ligand (H(2)CBA), resulting in a honeycomb arrayed framework. S-1 possesses excellent water stability and still retains intact structure after exposure to water for 10 weeks or boiling water for 10 weeks. Interestingly, S-1 acts as a luminescence sensor to selectively and sensitively detect quercetin with the limit of detection (LOD) as low as 0.23 ppm (7.6 x 10(-7) M). The relationship between relative luminescence intensity and concentration obeys linear in the range of 0-300 ppm (0-993 mu M), which allows quantitative detection of quercetin. Importantly, S-1 can be reused at least six times with almost no change in luminescent intensity. Compared with the high performance liquid chromatography-mass spectrometry (HPLC-MS) method, S-1 was used to determine the content of quercetin in onionskin and apple peel samples with satisfactory results. Furthermore, a portable S-1 test paper is also developed and expected to be applied in practice. To our knowledge, S-1 is the first example of MOFs as luminescent sensor for quercetin.