Efficient Epoxidation over Faujasite Zeolites: Unprecedented O2 Cooperative Activation by Co(II)–Ba(II) Cation Pair Sites Confined in the Supercage
Efficient Epoxidation over Faujasite Zeolites: Unprecedented O2 Cooperative Activation by Co(II)–Ba(II) Cation Pair Sites Confined in the Supercage
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DOI：
10.1021/acscatal.3c04904
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发表时间：
2023-11
期刊：
影响因子：
12.9
通讯作者：
Xue Yang;Zhangyun Liu;Boxu Gao;Zheng Chen;Kexin Yan;Sinong Wang;Yujian Xia;Yahong Zhang;Lei Wang;Xin Xu;Yi Tang
中科院分区：
文献类型：
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作者：
Xue Yang;Zhangyun Liu;Boxu Gao;Zheng Chen;Kexin Yan;Sinong Wang;Yujian Xia;Yahong Zhang;Lei Wang;Xin Xu;Yi Tang
环氧苯乙烯是重要的精细化学品和医药用环氧化物之一，但其目前的合成工艺对环境不友好。Co2+（Ba 2+）交换的八面沸石分子筛作为一种环境友好、安全的催化体系，被发现能有效地催化苯乙烯与分子氧的环氧化反应。尽管已经发现了近二十年，但活性位点的性质和反应机制仍然不清楚。在此，我们进行了详细的实验表征和密度泛函理论计算。结果表明，活性中心是双核的，而不是通常认为的单中心Co2+离子，其中Co2+···Co2+或Ba 2+···Co2+对协同激活O2生成O2-.与对称的Co ~（2+）··Co ~（2+）对位置相比，不对称的Ba ~（2+）··Co ~（2+）对位置上靠近Ba ~（2+）的末端氧对苯乙烯中的乙烯基C_（10）C_（10）C_（10）C这种新的见解将使氧化催化剂的优化。
Styrene oxide is one of the most important epoxides for manufacturing fine chemicals and pharmaceuticals, but its current synthesis process is environmentally unfriendly. As an eco-friendly and safe system, Co2+(Ba2+)-exchanged faujasite zeolites were found to efficiently catalyze styrene epoxidation with molecular oxygen. Despite having been discovered for nearly two decades, the nature of the active site and the mechanism of the reaction remain unclear. Herein, we carried out detailed experimental characterizations and density functional theory calculations. We concluded that the active sites are binuclear, rather than single-site Co2+ions as generally believed, where Co2+···Co2+or Ba2+···Co2+pairs cooperatively activate O2to O2–. As compared to that on the symmetric Co2+···Co2+pair site, the ethenyl C═C in styrene tends to be exclusively attacked by the terminal oxygen closer to Ba2+on the asymmetric Ba2+···Co2+pair site, thus enhancing the epoxidation selectivity. This new insight will enable the optimization of oxidation catalysts.