A new 3 D {Na₂Cu₃}-substituted polyoxometalate: synthesis, structure and its photocatalytic and electrochemical properties

A new 3 D polyoxometalate, H₇K₃[Na₂Cu₃(H₂O)(B-α-SbW₉O₃₃)₂]·8H₂O (1), has been hydrothermally made and characterized by IR spectroscopy, thermogravimetric analyses, powder X-ray diffraction and single crystal X-ray diffraction analysis. 1 crystallizes in the tetragonal system, space group P-42₁ m, with a = 16.7532(7) Å, b = 16.7532(7) Å, c = 13.8335(11) Å and Z = 2. Structure analysis reveals that the polyanion in 1 consists of two B-α-SbW₉O₃₃ ({SbW₉}) units sandwiched by a U-shaped {Na₂Cu₃} cluster made by two Na⁺ and three Cu²⁺ ions. The most prominent structural feature of 1 is that the [Na₂Cu₃(H₂O)(B-α-SbW₉O₃₃)₂]^10– ({Na₂Cu₃(SbW₉)₂}) units are connected to construct a 2 D network through Cu–O = W bridges. To the best of our knowledge, 1 represents the first sample with an unclosed central belt between two {SbW₉} fragments. Furthermore, neighboring 2 D networks connect by K⁺ cations to form a 3 D framework. The semiconductor behavior, electrochemical properties and photocatalytic activities have been investigated, showing excellent photocatalytic and electrocatalytic activities for the photodegradation of MB/RhB and bromate reduction.