{BW12O40} Hybrids Modified by in Situ Synthesized Rigid Ligand with Supercapacitance and Photocatalytic Properties.

Abstract

Organic rigid ligand-modified polyoxometalate-based materials possess complex and diverse structures, promising electrochemical energy storage properties and outstanding photocatalytic capabilities. Hence, two new [BW12O40]5-(abbreviated as {BW12O40})-based inorganic-organic hybrids [{Cu(en)2(H2O)}][{Cu(pdc)(en)}{Cu(en)2}(BW12O40)]·2H2O (1) and [{CuI5(pz)6(H2O)4}(BW12O40)] (2) (pdc = 2-picolinate, en = ethylenediamine, pz = pyrazine) were successfully synthesized through a hydrothermal method. Among them, pdc and pz were obtained by in situ transformation from 2,6-pyridinedicarboxylic acid (H2 pydc) and 2,3-pyrazinedicarboxylic acid (H2pzdc), respectively. In compound 1, the {BW12O40} clusters as an intermediate junction connect with {Cu(pdc)(en)}{Cu(en)2} and {Cu(en)2(H2O)} to form monomers, which in turn form supramolecular chains, sheets, and space network via hydrogen bonding. The {BW12O40} clusters are packed into copper-pyrazine frameworks in compound 2, and a unique polyoxometalate-based metal organic frameworks (POMOFs) structure with a new topology of {12}2{6.123.142}2{62.12.142.18}{62.123.16}{6}6 is formed via covalent bonds. When used as electrode materials for supercapacitors, the values of specific capacitance are 651.56 F g-1 for 1-GCE and 584.43 F g-1 for 2-GCE at a current density of 2.16 A g-1 and good cycling stability (90.94%, 94.81% of the initial capacity after 5000 cycles at 15.12 A g-1, respectively). The kinetic analysis reveals that surface capacitance plays a major role. Furthermore, both compounds can effectively degrade Rhodamine B (RhB) and Methylene blue (MB), showing the outstanding photocatalytic performance.