Metal–Organic Frameworks with Phosphotungstate Incorporated for Hydrolytic Cleavage of a DNA-Model Phosphodiester

Five phosphotungstate-incorporated metal–organic
frameworks
{[Eu4(dpdo)9(H2O)16PW12O40]}­(PW12O40)2·(dpdo)3·Cl3 (1); {ZnNa2(μ-OH)­(dpdo)4(H2O)4[PW12O40]}·3H2O (2); {Zn3(dpdo)7}­[PW12O40]2·3H2O (3); and [Ln2H­(μ-O)2(dpdo)4(H2O)2]­[PW12O40]·3H2O (Ln = Ho for 4 and
Yb for 5) (dpdo = 4,4′-bipyridine-N,N′-dioxide) have been synthesized through
a one-step hydrothermal reaction and characterized by elemental analyses,
infrared (IR) spectroscopy, photoluminescence, and single-crystal
X-ray diffraction (XRD). The structural analyses indicate that 1–5 display diversity structure from one-dimensional
(1D) to three-dimensional (3D) series of hybrids. Kinetic experiments
for the hydrolytic cleavage of DNA-model phosphodiester BNPP (bis­(p-nitrophenyl)­phosphate) were followed spectrophotometrically
for the absorbance increase at 400 nm in EPPS (4-(2-hydroxyethyl)­piperazine-1-propane
sulfonic acid) buffer solution, because of the formation of p-nitrophenoxide with 1–5 under conditions of pH 4.0 and 50 °C. Ultraviolet (UV) spectroscopy
indicate that the cleavage of the phosphodiester bond proceeds with
the pseudo-first-order rate constant in the range of 10–7–10–6 s–1, giving an inorganic
phosphate and p-nitrophenol as the final products
of hydrolysis. The results demonstrate that 1–5 have good catalytic activity and reusability for hydrolytic
cleavage of BNPP.