Insight into luminescence enhancement of coordinated water-containing lanthanide metal-organic frameworks by guest molecules

A series of isostructural lanthanide three-dimensional compounds [Ln(HL)(H2O)(2)]center dot guest (Ln = Tb or Eu, H4L = 2-(N,N-bis(4-methylbenzoic acid)amino)benzoic-1,4-dioic acid, guest = NMP, DMA, DMF or H2O) were assembled and characterized. Their luminescence intensities and quantum yields increase in the order of the guest molecules: NMP > DMA > DMF > H2O (NMP = N-methyl-2-pyrrolidone, DMA = N,N-dimethylacetamide, DMF = N,N-dimethylformamide). The investigation reveals that the hydrogen-bond formed between the metal-organic frameworks should be responsible for the luminescence enhancement of the compounds.