Boosting the catalysis of cesium phosphomolybdate encapsulated in hierarchical porous UiO-66 by microenvironment modulation for epoxidation of alkenes

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 52; no. 4; pp. 14676 - 14685
• Main Authors: Hu, Dianwen, Miao, Songsong, Zhang, Pengfei, Wu, Siyuan, He, Yu-Peng, Meng, Qingwei
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 17.10.2023
• Subjects: Alkenes; Benzene; Butyl hydroperoxide; Catalysis; Catalytic activity; Cesium; Composite materials; Encapsulation; Epoxidation; Functional groups; Metal-organic frameworks; Modulation; Polyoxometallates; Stability; Substitution reactions
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/d3dt02479b

The chemical microenvironment of polyoxometalates (POMs) encapsulated in metal-organic frameworks (MOFs) presents a significant influence on their catalytic performance, which can be easily regulated by the linker functional group alteration or metal substitution in MOFs. Herein, a series of cesium phosphomolybdate (CsPM) encapsulated in hierarchical porous UiO-66-X composites (CsPM@HP-UiO-66-X, X = H, 2CH 3 , or 2OH, where X represents the alterable group grafted onto the linker benzene ring) were successfully synthesized through a one pot modulated solvothermal method. The catalytic performances of the obtained materials were explored in alkene epoxidation reaction with tert -butyl hydroperoxide ( t -BuOOH). CsPM@HP-UiO-66-2CH 3 showed relatively high catalytic activity, stability, and epoxidation selectivity in cyclooctene epoxidation among the CsPM@HP-UiO-66-X composites. Moreover, CsPM@HP-UiO-66-2CH 3 was effective in the epoxidation of numerous alkenes, especially cyclic alkenes. The superior catalytic activity of CsPM@HP-UiO-66-2CH 3 is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites by introducing a hydrophobic methyl group. Meanwhile, the size-matched effect, the introduction of cesium cations, and the strong metal-support interactions (SMSIs) between CsPM and HP-UiO-66-2CH 3 play a crucial role in the stability of CsPM@HP-UiO-66-2CH 3 . CsPM@HP-UiO-66-2CH 3 showed preferable catalytic performance in alkene epoxidation reaction among CsPM@HP-UiO-66-X composites, which is mainly attributed to the modulation of the microenvironment surrounding CsPM active sites with a methyl group.