A novel polyoxometalate-based metal–organic framework templated by twin-Dawson clusters, [{Cu₃(μ₃-O)}₂(trz)₆Cu₂(H₂O)₁₃][H_1.73P₂As_1.73W_16.27O₆₂]·8.25H₂O (1) (trz = 1,2,4-triazole), has been synthesized under hydrothermal conditions. In 1, there are two crystal distinct motifs: a 3D metal–organic nanotube framework and seven-connected Dawson clusters. It is worth mentioning that the 3D framework possesses nanotube-like channels. The twin-H_1.73P₂As_1.73W_16.27O₆₂ clusters (abbreviated as P₂(As/W)₁₈ clusters) as templates occupy channels of the nanotube framework. To the best of our knowledge, this represents the first metal–organic nanotube framework templated by twin-Dawson clusters. The electrochemical experiments indicate that the 1-based glassy carbon electrode (1-GCE) possesses high catalytic efficiency and high stability toward reduction of inorganic bromate molecules and oxidation of the biological molecule ascorbic acid. The electrocatalytic efficiency towards the reduction of bromate in 1 M H₂SO₄ solution and oxidation of AA in N₂ purged solution is ca. 848.4% and 896.8% (catalytic substrate: 0.5 mM), respectively. The current signal after 100 cycles exhibits almost no loss for 1-GCE.