Nonconductive two-dimensional metal−organic frameworks for high-performance electrochemical energy storage

Most metal-organic frameworks (MOFs) cannot be used as electrode materials due to their high cost, poor stability in aqueous solutions, inferior intrinsic electrocatalytic activity , and poor conductivity. The novel application of a nickel (II) cluster-based two-dimensional MOF, Ni-mba ([Ni(II) 6 Ni(III) 2 (mba) 6 (Cl) 2 (OH − ) 2 (O 2− )] n , H 2 mba is 2-mercaptobenzoic acid), is reported for use as electrode materials. Ni-mba is an insulator and H 2 mba is an inexpensive chemical raw material. The conductivity of Ni-mba is 2.180 × 10 −9 Scm −1 at 30 °C. The electrocatalytic activity of Ni-mba is enhanced by the hexanuclear nickel (II) cluster subunit containing the sulfhydryl group and the mixed valence Ni 2+ /Ni 3+ ions. Ni-mba shows excellent performance, stability in 6 M KOH, and a high inherent density (1.828 gcm −3 ) and specific capacity (704.4 Fg −1 at 1 Ag −1 and 1088.5 mAhg −1 at the first cycle) for lithium-ion batteries and supercapacitors . This paper provides a novel application of nonconductive two-dimensional MOFs in the energy storage field and the design recommendations of high-performance electrode materials for energy conversion and storage based on its structure and performance differences.