Polyoxometalate-Incorporated Metallapillararene/Metallacalixarene Metal-Organic Frameworks as Anode Materials for Lithium Ion Batteries

A series of remarkable crystalline compounds containing metallapillararene/metallacalixarene metal-organic frameworks (MOFs), [Ag 5 (pyttz) 3 ·Cl·(H 2 O)][H 3 SiMo 12 O 40 ]·3H 2 O ( 1 ), [Ag 5 (trz) 6 ][H 5 SiMo 12 O 40 ] ( 2 ), [Ag 5 (trz) 6 ][H 5 GeMo 12 O 40 ] ( 3 ), and [Ag 5 (trz) 6 ][H 4 PW 12 O 40 ] ( 4 ) (pyttz = 3-(pyrid-4-yl)-5-(1 H -1,2,4-triazol-3-yl)-1,2,4-triazolyl, trz = 1,2,4-triazole), have been obtained by using a simple one-step hydrothermal reaction of silver nitrate, pyttz for 1 and trz for 2 – 4, and Keggin type polyoxometalates (POMs). Crystal analysis reveals that Keggin POMs have been successfully incorporated in the windows of the metallapillararene/metallacalixarene MOFs in compounds 1 – 4 . In addition, the Keggin silicomolybdenate-based hybrid compounds 1 and 2 were used as anode materials in lithium ion batteries (LIBs), which exhibited promising electrochemical performance with the first discharge capacities of 1344 mAh g –1 for 1 and 1452 mAh g –1 for 2, and this stabilized at 520 mAh g –1 for 1 and 570 mAh g –1 for 2 after 100 cycles at a current density of 100 mA g –1 . The performances are better than that of (NBu 4 ) 4 [SiMo 12 O 40 ] matrix and commercial graphite anodes.