Copper–Organic Cationic Ring with an Inserted Arsenic–Vanadium Polyanionic Cluster for Efficient Catalytic Cr<sup>VI</sup> Reduction Using Formic Acid

Polyanionic cluster [β-As<sub>8</sub>V<sub>14</sub>O<sub>42</sub>(H<sub>2</sub>O)]<sup>4–</sup> is well embedded in a large porous eight-membered cationic ring of the copper ligand, giving a stable host–guest supramolecular system. The assembly exhibits an efficient heterogeneous catalytic performance for the reduction of Cr<sup>VI</sup> using formic acid at ambient temperature.