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.