While catalysis is highly dependent on the electronic structure of catalyst, the understanding on catalytic performance affected by electron spin regulation remains challenging and rare. Herein, we have developed a facile strategy to the manipulation of the cobalt spin state over covalent organic frameworks (COFs), COF-367-Co, by simply changing the oxidation state of Co centered in the porphyrin. Density functional theory (DFT) calculations together with experimental results confirm that CoII and CoIII are embed-ded in COF-367 with S = 1/2 and 0 spin ground states, respectively. Remarkably, photocatalytic CO2 reduction results indicate that COF-367-CoIII exhibits favorable activity and significantly enhanced selectivity to HCOOH, accordingly much reduced activ-ity and selectivity to CO and CH4, in sharp contrast to COF-367-CoII. The results highlight that spin-state transition of cobalt greatly regulates photocatalytic performance. Theoretical calculations further disclose that the present of CoIII in COF-367-Co is preferable to the formation of HCOOH but detrimental to its further conversion, which clearly accounts for its distinctly different photocatalysis over COF-367-CoII. To the best of our knowledge, this is the first report on regulating photocatalysis by spin state manipulation in COFs.

中文翻译：

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通过共价有机框架中钴的自旋态操作调节光催化

虽然催化高度依赖于催化剂的电子结构，但对受电子自旋调节影响的催化性能的理解仍然具有挑战性且很少见。在此，我们开发了一种简便的策略，通过简单地改变以卟啉为中心的 Co 的氧化态，来操纵共价有机框架 (COF) COF-367-Co 上的钴自旋态。密度泛函理论 (DFT) 计算和实验结果证实 CoII 和 CoIII 分别嵌入到 COF-367 中，S = 1/2 和 0 自旋基态。值得注意的是，光催化 CO2 还原结果表明 COF-367-CoIII 表现出良好的活性并显着提高了对 HCOOH 的选择性，因此大大降低了对 CO 和 CH4 的活性和选择性，与 COF-367-CoII 形成鲜明对比。结果表明，钴的自旋态转变极大地调节了光催化性能。理论计算进一步表明，COF-367-Co 中 CoIII 的存在优于 HCOOH 的形成，但不利于其进一步转化，这清楚地解释了其与 COF-367-CoII 明显不同的光催化作用。据我们所知，这是关于通过 COF 中的自旋态操纵调节光催化的第一份报告。