Covalent Organic Framework Constructed by Clicking Azido Porphyrin with Perpropargyloxy-Cucurbit[6]uril for Electrocatalytic Hydrogen Generation from Water Splitting

In the present study, we describe the synthesis and characterization of a new covalent organic framework (COF-TPP-CB[6]) which was assembled together by clicking perpropargyloxy cucurbit[6]uril (CB[6]) to the azido-functionalized tetraphenylporphyrin (TPP-4N3) through a copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC). Perpropargyloxy CB[6] was synthesized through the direct oxidation of CB[6] to afford perhydroxy CB[6] followed by subsequent O-propargylation using NaH. We also demonstrated that the resulting framework (COF-TPP-CB[6]) can be employed as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) in alkaline medium upon loading it with a nickel cocatalyst. The effect of TiO2 and different loadings of Ni on the HER performance of TPP-CB[6] was also studied. Herein, 12%Ni@TPP-CB[6] as the optimum catalyst showed an impressive H2 production rate of 18.7 mmol h–1 g–1 with a low onset potential of −250 mV.