Photophysical Tuning of Viologen-Based Metal–OrganicFramework Hybrids via Anion Exchange and Chemical Sensing on Persulfate(S 2 O 8 2– )

Viologen-based metal organic frameworks have generally been used in a variety of applications because of the fact that their counter anions can be exchanged by different anion guests. A cationic [Cd2Cl(m-bpybdc)2(H2O)4](NO3)3·7H2O (Cd-MOF) (m-bpybdc = 1,1′-bis(3-carboxyphenyl)-4,4′-bipyridinium) is selected for ion exchanging a series of anions with NO3– in its pore and the resulting hybrids show good structural stability. It is found that the luminescence emission intensity of S2O82–@Cd-MOF [Cd-MOF exchanged with persulfate (S2O82–)] is much stronger than that of parent Cd-MOF and other hybrids Cd-MOF was exchanged by other anions. The results suggest that viologen-based Cd-MOF can be regarded as a luminescent sensor for S2O82– based on their photoinduced electron transfer process from each other. Cd-MOF shows good selectivity of S2O82– over other anions and sensitivity as well as quick response after 2 min. For the first time, the detection of S2O82– is realized through the luminescence enhancement of v...