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

Abstract

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<sub>8</sub>-pyrazolate scaffold. Unlike the full 12 connections of the Ni<sub>8</sub>(OH)<sub>4</sub>(H<sub>2</sub>O)<sub>2 </sub>clusters<b> </b>in other<b> </b>Ni<sub>8</sub>-pyrazolate networks, significant linker deficiency was observed here,<b> </b>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<b> </b>crystalline Ni<sub>8</sub>-pyrazolate scaffold also retains the crystalline order even after thermal treatments (up to 300 °C) that served to partially graphitizes the neighboring alkyne units. The resultant nanographene components enhance the electroactive properties of the porous hosts, achieving<b> </b>hydrogen evolution reaction (HER) activity that rivals topical nickel/palladium-enabled materials.

A highly stable Zn9-pyrazolate metal–organic framework with metallosalen ligands as a carbon dioxide cycloaddition catalyst

“…42 The MOF adopts a two-fold interpenetration structure, which is unprecedented in previous Ni 8 ( pyrazolate) MOFs. [42][43][44][45] The Zn 9 cluster of one network is located in the tetrahedral cavity formed by another network with 50% occupancy (Fig. S4 †).…”

Insight into Stable, Concentrated Radicals: from Sulfur-functionalized Alkyne-rich Crystalline Frameworks to Simple Alkyne Motifs

“…This hypothesis connects naturally to our ongoing works on alkyne annulation. [37][38][39][40][41][42] In solution chemistry, similar cyclizations (e.g., Bergman cyclization for 1,2-dialkynylarenes) are intended for well-defined, discrete molecular products, and metal catalysts/hydrogen donors are used for promoting selectivity and minimizing side reactions (e.g., from the reactive radical intermediates). [43][44][45][46][47][48] Our motivation, however, lies in the solid state; notice that in the solid state, cascade cyclizations to form polycyclic aromatics have been conducted, but, curiously, with no mention of radical species in the annulated products.…”