2D- MOFs with Ni(II), Cu(II) and Co(II) as Efficient Oxygen Evolution Electrocatalysts: Rationalization of Catalytic Performance vs Structure of the MOFs and Potential of the Redox Couples.

Earth abundant transition-metal based Metal Organic Frameworks (MOFs) are of immense interest for the development of efficient and durable heterogeneous water splitting electrocatalysts. This repot explores the design of 2D- MOFs with redox active metal centres (Ni(II), Co(II) and Cu(II)), containing two types of electron rich linkers such as bis(5-azabenzimidazole, linear L1 and angular L2) and aromatic dicarboxylates. The electron rich linkers are considered to stabilize the higher oxidation state of the redox active metal centers in the course of electrocatalytic OER process. The 2D- MOFs of L1 and L2 with Co(II) (1 & 3) and Ni(II) (2 & 4) have been produced via the conventional hydrothermal synthesis while the MOFs of Cu(II) (Cu@1 and Cu@3) are obtained by the post synthetic transmetallation reaction of MOFs 1 and 3. The elctrocatalytic OER activity of the six MOFs have been studied to explore the influence of the redox potential of the transition-metal quasi-reversible couples and the coordination environment around the redox active metal centres in the electrocatalytic activity. The lowest overpotential of 370 mV exhibited by MOF 2 with the highest current density and TOF value indicates the importance of the presence of coordinated water molecules and the lowest redox potential value of the most favorable quasi-reversible couple Ni+2/Ni+3. These catalysts exhibit a remarkable stability upto 1000 OER cycles. These studies pave the way for the design of MOF materials towards the development of promising heterogeneous OER electrocatalyst.