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Photophysical Tuning of Viologen-Based Metal–Organic Framework Hybrids via Anion Exchange and Chemical Sensing on Persulfate (S₂O₈²–)

Zhao, Jing, Qu, Xianglong, Wang, Jinmin, Yan, Bing
Industrial & engineering chemistry process design and development 2019 v.58 no.40 pp. 18533-18539
adsorption, aniline, anion exchange, anions, coordination polymers, dyes, electron transfer, electrostatic interactions, emissions factor, luminescence, nitrates, process design
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 viologen-based Cd-MOF. In addition, Cd-MOF displays a certain adsorption ability on Acid Black 1 (419 mg·g–¹) and methyl blue (484 mg·g–¹) via the electrostatic interaction between its cationic framework and the aniline anion dyes.