The electroreduction of CO₂ to value-added chemicals is a promising approach to utilize CO₂ and mitigate greenhouse gas emission. Covalent organic frameworks (COFs) with abundant accessible active sites, tunable pore size, and large CO₂ adsorption capacity are considered promising electrocatalysts for CO₂ conversion. However, most COFs linked by reversible covalent bonds exhibit poor stability, which limits their application for CO₂ electroreduction reactions in acidic or alkaline electrolytes. Herein, a Ni-phthalocyanine-based COF linked by stable imidazole building blocks, named NiPc-Im-COF, was synthesized through the condensation reaction of 2,3,9,10,16,17,23,24-octa-aminophthalocyaninato Ni(II) and 4,4′-biphenyl dialdehyde. The obtained NiPc-Im-COF exhibits high chemical stability after soaking in concentrated HCl and KOH. When applied for the electroreduction of CO₂, the NiPc-Im-COF exhibits high CO selectivity (>90%) in electrolytes with different pH values. Specifically, the NiPc-Im-COF shows a high CO partial current density of 267 mA cm⁻² with a CO selectivity of 90% at −0.8 V vs. the reversible hydrogen electrode (RHE) in 5 M KOH solution, and meanwhile, over 90% of FE_CO and 6 hours of stability at −1.3 V in 0.5 M K₂SO₄ (pH = 1). The XRD patterns prove that the structure of the NiPc-Im-COF is not destroyed after CO₂ electroreduction at different pH values. This work presents a strategy to improve the stability of COFs via irreversible covalent linkage and offers an efficient CO₂RR in the full pH range, which paves a new pathway for the industrial application of COFs in CO₂ electroreduction.

中文翻译：

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坚固的咪唑连接的镍酞菁基共价有机框架，用于在整个 pH 范围内进行 CO2 电还原

_{将CO 2}电还原为增值化学品是利用CO ₂和减少温室气体排放的一种有前途的方法。共价有机骨架（COF）具有丰富的活性位点、可调的孔径和大的CO ₂吸附容量，被认为是有前途的CO ₂转化电催化剂。然而，大多数通过可逆共价键连接的COF稳定性较差，这限制了它们在酸性或碱性电解质中CO ₂电还原反应的应用。在此，通过2,3,9,10,16,17,23,24-八氨基酞菁镍的缩合反应合成了一种由稳定的咪唑结构单元连接的镍酞菁基COF，命名为NiPc-Im-COF。 ( II )和4,4'-联苯二醛。所得NiPc-Im-COF在浓HCl和KOH中浸泡后表现出较高的化学稳定性。当应用于CO ₂的电还原时，NiPc-Im-COF在不同pH值的电解质中表现出高CO选择性(>90%)。具体来说，NiPc-Im-COF在5 M KOH溶液中表现出267 mA cm ^-2的高CO部分电流密度，在-0.8 V时相对于可逆氢电极（RHE）的CO选择性为90% ，同时，超过 90% 的 FE _{CO ，在 0.5 MK 2} SO ₄ (pH = 1)中 -1.3 V 下稳定 6 小时。 XRD图谱证明NiPc-Im-COF在不同pH值下进行CO ₂电还原后结构没有被破坏。该工作提出了一种通过不可逆共价键提高COF稳定性的策略，并在整个pH范围内提供高效的CO _{2 RR，这为COF在CO 2}电还原中的工业应用开辟了新途径。