Linker Deficiency, Aromatic Ring Fusion, and Electrocatalysis in a Porous Ni₈-Pyrazolate Network

The cruciform linker molecule here features two designer functions: the pyrazole donors for framework construction, and the vicinal alkynyl units for benzannulation to form nanographene units into the Ni-8-pyrazolate scaffold. Unlike the full 12 connections of the Ni-8(OH)(4)(H2O)(2) clusters in other Ni-8-pyrazolate networks, significant linker deficiency was observed here, leaving about half of the Ni(II) sites capped by acetate ligands, which can be potentially removed to open the metal sites for reactivity. The crystalline Ni-8-pyrazolate scaffold also retains the crystalline order even after thermal treatments (up to 300 degrees C) that served to partially graphitize the neighboring alkyne units. The resultant nanographene components enhance the electroactive properties of the porous hosts, achieving hydrogen evolution reaction (HER) activity that rivals that of topical nickel/palladium-enabled materials.