Five Keggin-Type Polymolybdates Based on Ag/Cu/Co–Organic Complexes for Enhanced Capacitance of Supercapacitors

The design and construction of low-cost and high-efficiency electrode materials represent a meaningful and challenging issue for electrochemical energy storage. In this work, we aim to construct metal–organic complex (MOC)-modified polymolybdates with high performance for supercapacitors. Five new polymolybdate-based MOCs were obtained by reacting with different metal ions under different temperature and solvent conditions: [{Ag 4 (BTYE) 3 }{SiMo 12 O 40 }]·4H 2 O ( 1 ), [{Cu 4 (BTYE) 3.5 }{SiMo 12 O 40 }]·4H 2 O ( 2 ), [{Cu 3 (BTYE) 3 }{SiMo 12 O 40 }]·7H 2 O ( 3 ), [{Co 2 (BTYE) 4 }{SiMo 12 O 40 }] ( 4 ), and [{Co(BTYE) 3 }{SiMo 12 O 40 }]·2H 2 O ( 5 ) (BTYE = bis(1,2,4-triazol-1-yl)ethane). In compounds 1 and 2, {SiMo 12 }, as the multi-connected nodes, merged into the 3D Ag/Cu–organic complexes to yield the 3D POM-based MOCs. In compound 3, the 1D Cu–organic complexes and 1D Cu–{SiMo 12 } inorganic chains are joined together to produce the 3D POM-based MOCs. In compound 4, {SiMo 12 }, as the two-connected nodes, is situated in the 2D Co–organic complexes to form a 3D POM-based Co–organic complex. Compound 5 displays a 1D Co–organic complex. All five POM-based MOCs exhibited excellent specific capacitance of 447.5 F·g –1, 278.6 F·g –1, 204.175 F·g –1, 391.9 F·g –1, and 289.6 F·g –1 at 1 A·g –1, respectively, as well as long-term stability with a capacitance conservation rate of 88.6% for 1, 86.2% for 2, and 87.1% for 4 after 1000 cycles. The results of this work provide inspiration and direction for the building of POM-based MOCs with broad application potentials in high-performance energy storage apparatuses.