化学
催化作用
双功能
X射线吸收光谱法
甲醇
金属有机骨架
热分解
碳酸氢盐
无机化学
金属
解吸
氢
产量(工程)
吸收光谱法
物理化学
有机化学
吸附
材料科学
冶金
物理
量子力学
作者
Jingzheng Zhang,Bing An,Zhe Li,Yonghua Cao,Yiheng Dai,Wangyang Wang,Lingzhen Zeng,Wenbin Lin,Cheng Wang
摘要
ZrZnOx is active in catalyzing carbon dioxide (CO2) hydrogenation to methanol (MeOH) via a synergy between ZnOx and ZrOx. Here we report the construction of Zn2+–O–Zr4+ sites in a metal–organic framework (MOF) to reveal insights into the structural requirement for MeOH production. The Zn2+–O–Zr4+ sites are obtained by postsynthetic treatment of Zr6(μ3-O)4(μ3-OH)4 nodes of MOF-808 by ZnEt2 and a mild thermal treatment to remove capping ligands and afford exposed metal sites for catalysis. The resultant MOF-808-Zn catalyst exhibits >99% MeOH selectivity in CO2 hydrogenation at 250 °C and a high space-time yield of up to 190.7 mgMeOH gZn–1 h–1. The catalytic activity is stable for at least 100 h. X-ray absorption spectroscopy (XAS) analyses indicate the presence of Zn2+–O–Zr4+ centers instead of ZnmOn clusters. Temperature-programmed desorption (TPD) of hydrogen and H/D exchange tests show the activation of H2 by Zn2+ centers. Open Zr4+ sites are also critical, as Zn2+ centers supported on Zr-based nodes of other MOFs without open Zr4+ sites fail to produce MeOH. TPD of CO2 reveals the importance of bicarbonate decomposition under reaction conditions in generating open Zr4+ sites for CO2 activation. The well-defined local structures of metal-oxo nodes in MOFs provide a unique opportunity to elucidate structural details of bifunctional catalytic centers.
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