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

Abstract

A robust\nand porous Ni-based metal–organic framework (MOF),\nNi<b>L1</b>, was assembled from Ni(II) ions and a dipyrazolate\nlinker (<b>L1</b>^2–). A Ni(II)-anchored MOF\ncatalyst Ni@Ni<b>L1</b>-Sal has been successfully prepared by\npost-synthetic modification (PSM) condensation between Ni<b>L1</b> with salicylaldehyde, followed by chelation of Ni(II) ions by salicylaldimine\nas a secondary active site. Ni@Ni<b>L1</b>-Sal with carbon black\nwas found to exhibit enhanced electrocatalytic hydrogen evolution\nreaction (HER) performance (the smallest overpotential, 384 mV, and\nTafel slope, 87 mV dec^–1) when compared with primitive\nNi<b>L1</b> and Ni<b>L1</b>-Sal. Such improvement in HER\nhighlights the creation of unambiguous secondary active sites as an\navenue to the rational design of a functional MOF-based electrocatalyst.