Four octamolybdate–based hybrid compounds consisting of phenanthroline derivative ligands with photocatalytic and capacitive performances

Employing polyoxometalate–based hybrid materials combined from metal–organic complex and polyoxometalate as photocatalysts for pollutant degradation and capacitive electrodes has become a research focus. In order to continue to develop the potential photocatalysts and electrode materials, four octamolybdate–based hybrids constructed from phenanthroline derivative ligands 1, 10 − phenanthroline − 5, 6 − dione (PDO) and 1, 10 − phenanthroline − 5, 6 − diamine (PDA) were isolated. The [β − Mo₈O₂₆]⁴⁻ anions were involved in the structures of 1–3, which were aggregated by Cu ions into a two–dimensional layer decorated by PDO or PDA ligands in 1 and 2, but discrete and coexist with [Co(H₂O)₂(PDO)₂]²⁺ metal–organic components in 3. 4 featured [α − Mo₈O₂₆]⁴⁻ anions bi–supported by two [Co(H₂O)(PDA)₂]²⁺ metal–organic fragments. The introduction of metal–organic complexes of metal/PDO or PDA improved the light absorption, conductivity and electrochemical active surface area of these hybrid compounds. Consequently, compounds 1–4 as photocatalysts showed photocatalytic activity for degradation of organic dyes with good recyclability and stability at least 3 cycles. The possible photocatalytic degradation mechanism was discussed. Additionally, compounds 1–4 employed as electrode materials demonstrated good capacitive performances, especially 4 with the specific capacitance of 1385.3F g⁻¹ at the current density of 1 A/g.