Discrete Arsonate-Grafted Inverted-Keggin 12-Molybdate Ion [Mo 12 O 32 (OH) 2 (4-N 3 C 2 H 2 -C 6 H 4 AsO 3 ) 4 ] 2- and Formation of a Copper(II)-Mediated Metal-Organic Framework.

The discrete inverted-Keggin ion [Mo 12 O 32 (OH) 2 (4-N 3 C 2 H 2 -C 6 H 4 AsO 3 ) 4 ] 2- ( 1 ) has been prepared in an aqueous acidic (pH 0.8) medium by the reaction of MoO 3 with the (4-triazolylphenyl)arsonic acid 4-N 3 C 2 H 2 -C 6 H 4 AsO 3 H 2 under hydrothermal conditions and was isolated as a sodium salt in 21% yield. The exact same reaction in the presence of Cu 2+ ions resulted in the neutral metal-organic framework (MOF) Cu 2 [Mo 12 O 34 (4-N 3 C 2 H 2 -C 6 H 4 AsO 3 ) 4 ] ( Cu-1 ) in 68% yield. The inverted-Keggin ion 1 comprises a metal-oxo core, which is capped by four organoarsonate groups, and in Cu-1 , individual polyanions are linked in the solid state by coordination of the Cu 2+ ions with the triazolyl groups. The discrete ion 1 was characterized by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic absorption (AA) spectroscopy, as well as thermogravimetric analysis (TGA), and the POM-MOF Cu-1 was characterized by single-crystal and powder XRD, FT-IR, TGA, and gas sorption. Cu-1 has channels with a diameter of around ∼0.9 nm and exhibits a water-vapor adsorption capacity of 89.7 cm 3 g -1 ( p / p 0 = 0.95).