Green synthesis of a redox-active riboflavin-integrated Ni-MOF and its versatile electrocatalytic applications towards oxygen evolution and reduction, and HMF oxidation reactions

The post-synthetic modification (PSM) of metal-organic frameworks (MOFs) with redox-active molecules under mild conditions is a highly challenging approach to modify the inherent properties of MOFs without altering their crystallinity and other characteristics. Here, we prepared a single crystal Ni-MOF with a two-dimensional rod-like morphology. Furthermore, we utilized the PSM technique to incorporate redox-active riboflavin (Rbf) in the Ni-MOF using a green and facile mechanochemical method under solvent-free conditions. The Rbf-doped Ni-MOF (Rbf-Ni-MOF) showed a 4-fold increase in conductivity compared to the pristine Ni-MOF. We employed the Rbf-Ni-MOF as a multifunctional electrocatalyst towards the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and oxidation of 5-hydroxymethylfurfural (HMF). As an OER electrocatalyst, the Rbf-Ni-MOF delivered a high current density of 580 mA cm−2, which is around 26-fold greater than those of Rbf and the pristine Ni-MOF. The prep...