Continuous Electrosynthesis of Pure HO Solution with Medical-Grade Concentration by a Conductive Ni-Phthalocyanine-Based Covalent Organic Framework.

Electrosynthesis of HO provides an environmentally friendly alternative to the traditional anthraquinone method employed in industry, but suffers from impurities and restricted yield rate and concentration of HO. Herein, we demonstrated a Ni-phthalocyanine-based covalent-organic framework (COF, denoted as ) with a higher inherent conductivity of 1.14 × 10 S m, which exhibited an ultrahigh current density of 530 mA cm with a Faradaic efficiency (HO) of ∼100% at a low cell voltage of 3.5 V. Notably, this high level of performance is maintained over a continuous operation of 200 h without noticeable degradation. When integrated into a scale-up membrane electrode assembly electrolyzer and operated at ∼3300 mA at a very low cell voltage of 2 V, continuously yielded a pure HO solution with medical-grade concentration (3.5 wt %), which is at least 3.5 times higher than previously reported catalysts and 1.5 times the output of the traditional anthraquinone process. A mechanistic study revealed that enhancing the π-conjugation to reduce the band gap of the molecular catalytic sites integrated into a COF is more effective to enhance its inherent electron transport ability, thereby significantly improving the electrocatalytic performance for HO generation.