Assembly of\nFour Ternary Polyoxometalate Aggregates\nby Integrating Presynthesized {XW<sub>9</sub>Nb<sub>3</sub>O<sub>40</sub>} (X = Si/Ge) Units Using Molybdenum-Oxo Clusters

Polyoxometalates (POMs) have good potential for applications\nin\ndifferent fields, including conducting materials, optics, and electrocatalysis.\nOf particular significance is the synthesis and development of addendum\nPOMs. Molybdenum-oxo clusters, which are renowned for their diverse\nstructures and electronic properties, were utilized to facilitate\nthe synthesis of innovative materials. Herein, we employed presynthesized\n{XW<sub>9</sub> Nb<sub>3</sub>O<sub>40</sub>} (X= Si/Ge) polyanions\nas secondary building units and different molybdenum-oxo clusters\nas linkers. Four new addendum POMs were constructed, including two\ndimeric compounds Cs<sub>10</sub>[H<sub>2</sub>(SiW<sub>9</sub>Nb<sub>3</sub>O<sub>40</sub>)<sub>2</sub>(Mo<sub>2</sub>O<sub>4</sub>C<sub>2</sub>O<sub>4</sub>)]·19H<sub>2</sub>O (<b>1</b>) and\nCs<sub>8</sub>[H<sub>4</sub>(GeW<sub>9</sub>Nb<sub>3</sub>O<sub>40</sub>)<sub>2</sub>(Mo<sub>2</sub>O<sub>4</sub>C<sub>2</sub>O<sub>4</sub>)]·17H<sub>2</sub>O (<b>2</b>), and two tetrameric compounds\nCs<sub>15</sub>(NH<sub>4</sub>)[(SiW<sub>9</sub>Nb<sub>3</sub>O<sub>40</sub>)<sub>4</sub>(Mo<sub>4</sub>O<sub>6</sub>)]·42H<sub>2</sub>O (<b>3</b>) and Cs<sub>10</sub>K<sub>5</sub>[H(GeW<sub>9</sub>Nb<sub>3</sub>O<sub>40</sub>)<sub>4</sub>(Mo<sub>4</sub>O<sub>6</sub>)]·39H<sub>2</sub>O (<b>4</b>). Notably, this is\nthe first report of Mo/W/Nb ternary mixed-addendum POMs. In addition,\ncompounds <b>3</b> and <b>4</b> facilitate the transfer\nof protons through extended hydrogen-bonding networks with conductivity\nvalues of 1.16 × 10<sup>–2</sup> and 7.73 × 10<sup>–3</sup> S·cm<sup>–1</sup> at 85 °C and 98%\nrelative humidity, respectively. Furthermore, no discernible decline\nin conductivity was noted over the course of 10 h.