Multi-functionalized MOFs with large-pore apertures as luminescent probes for efficient sensing of quinones

Abstract

Extensive research over the past few years has been carried out on the synthesis of MOFs with high internal surface areas; however, introducing functional groups on their backbones at the same time is an ongoing challenge. Achieving MOFs with large pore apertures and at the same time having desirable functional groups is always a long-standing challenge since using longer links results in interpenetrating structures or instability. On the other hand, the crystalline nature of MOFs allows access to monitor and control host–guest interactions between structures and guest molecules. To better understand the effect of the structure and positions of functional groups on applications, a platform of azo (azobenzene-4,4-dicarboxylic acid (adc)) and azine (2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh)) containing MOFs has been designed and synthesized and used as a fluorescent probe for 1,8-dihydroxyanthraquinone (Danthron). Due to the flexible, polarizable, strong guest binding affinity and basic nature of these nitrogen-based groups, the resulting mixed linker MOFs can disclose fascinating structures along with imparting new properties. TMU-84 ([Cd(adc)(4-bpdh)].1.5DMF) and TMU-85 ([Zn_1.5(adc)_1.5(4-bpdh)]) are capable of distinguishing complementary and mismatched target sequences with high sensitivity and a significant K_sv (6572) value.