Ni(II)-Pyrazolate Framework Bearing a Metalated Schiff-Base Moiety for Electrocatalytic Hydrogen Evolution.

A robust and porous Ni-based metal-organic framework (MOF), Ni L1 , was assembled from Ni(II) ions and a dipyrazolate linker ( L1 2- ). A Ni(II)-anchored MOF catalyst Ni@Ni L1 -Sal has been successfully prepared by post-synthetic modification (PSM) condensation between Ni L1 with salicylaldehyde, followed by chelation of Ni(II) ions by salicylaldimine as a secondary active site. Ni@Ni L1 -Sal with carbon black was found to exhibit enhanced electrocatalytic hydrogen evolution reaction (HER) performance (the smallest overpotential, 384 mV, and Tafel slope, 87 mV dec -1 ) when compared with primitive Ni L1 and Ni L1 -Sal. Such improvement in HER highlights the creation of unambiguous secondary active sites as an avenue to the rational design of a functional MOF-based electrocatalyst.