Eu-MOF and its mixed-matrix membranes as fluorescent sensor for quantitative ratiometric pH and folic acid detection, and visible fingerprint identifying

Here, we demonstrate the assembly of a new stable lanthanide-based metal-organic framework (MOF), Eu(HDPB)(phen) (1) (HDPB = (1,1ʹ:3ʹ,1ʹʹ-terphenyl)-3,3ʹʹ,5,5ʹʹ-tetracarboxylic acid, phen = 1,10-phenanthroline), with a three-dimensional framework under solvothermal conditions. 1 showed a strong red fluorescent emission at room temperature and could be used as a selective and sensitive chemical sensor for pH and folic acid (FA) detection. Moreover, 1 could also be applied as a fluorescent material for visible identifying the fingerprints. Then, using 1 as filler, 1@poly(e-caprolactone) (PCL) and 1@poly(vinylidene difluoride) (PVDF), two mixed-matrix membranes (MMMs) have been fabricated. Notably, owing to hydrophobic protection of polymer matrix for MOF particles, these two MMMs also exhibited fluorescent emission comparable to 1 and could be used for FA sensing with good selectivity and remarkable recyclability. More importantly, this is the first time that Eu-MOF based MMMs employed in FA detection. The fabrication of MOFs-based MMMs not only provides a facile way for sensing biomarkers but also enhances the recyclability of sensors.