An Unconventional Phosphotungstate Constructed from Pentavacant [PW7O29]11- Building Blocks With Peroxidase-Like...

An unconventional phosphotungstate (CH6N3)10[Na2(H2O)4(P4W14O58)]·8H2O (1), was synthesized and structurally characterized. Single-crystal X-ray diffraction analysis shows that compound 1 features a [Na2(H2O)4(P4W14O58)]10- polyanion, in which two [PW7O29]11- units are connected through two P atoms and two [Na(H2O)2]+ bridges. Compound 1 exhibits remarkable peroxidase-like activity under acidic conditions (pH 3.0), efficiently catalyzing the H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to its blue oxidized product (ox-TMB). Steady-state kinetic studies demonstrate that 1 possesses strong affinity for both TMB and H2O2, with Michaelis constants (Km) of 0.25 mM and 3.73 mM, respectively. Leveraging its excellent catalytic performance, a facile and sensitive colorimetric method for H2O2 detection was established, offering a linear range of 5-700 μM and a detection limit of 2.19 μM. This work not only expands the structural diversity of highly lacunary polyoxometalates (POMs) but also provides new insights into the design and application of POM-based nanozymes.