Through
the powerful hydrothermal method, five rare-earth (Re = Dy, Gd, Ho,
Pr, and Sm) three-dimensional (3D) cluster-based metal–organic
frameworks (MOFs) have been synthesized, namely, [Dy(L)(H2O)(DMF)]
n
(1), {[Gd(L)(H2O)(DMF)]·DMF}
n
(2), {[Ho(L)(H2O)(DMF)]·0.5DMF}
n
(3), {[Pr(L)(H2O)(DMF)]·0.5DMF}
n
(4), and {[Sm(L)(H2O)1.55(DMF)0.45]·DMF}
n
(5; H3L = terphenyl-3,4″,5-tricarboxylic
acid), which have been determined by single crystal X-ray analyses
and PXRD characterization. Structural analyses reveal that, in 1–5, these L3– ligands
are linked by five different rare-earth centers, forming the iso-structural
nanoporous frameworks. PXRD patterns of bulky samples 1–5 also are consistent with theoretical PXRD
patterns confirming their purity. Solid state photoluminesce of free
H3L and 1–5 at room temperature
also has been investigated indicating strong ligand-based emissions.
Besides these, fluorescent dye Rhodamine B (RhB) can be introduced
into MOF1 forming the composite material RhB@MOF1 with a high quantum yield of 35%. It is noted that, through deliberately
tuning the morphologies of nanoparticle MOF1 under different
ultrasonic conditions, RhB@MOF1 can be utilized as the
first ratiometric fluorescent sensor to effectively discriminate l- and d-lysine from other amino acid molecules with
high K
sv values and low LOD values. On
the other hand, 2 was for the first time to be utilized
as an excellent bifunctional MOFs-based sensing platform to detect
insulin and Al3+ with a low detection limit in the human
serum solution.