Sulfonic acid-functionalized core-shell Fe3O4@carbon microspheres as magnetically recyclable solid acid catalysts

• Published in: Chinese chemical letters Vol. 32; no. 6; pp. 2079 - 2085
• Main Authors: Yuan, Chenyi, Wang, Xiqing, Yang, Xuanyu, Alghamdi, Abdulaziz A., Alharthi, Fahad A., Cheng, Xiaowei, Deng, Yonghui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2021; State Key Lab of Transducer Technology,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China%Department of Chemistry,State Key Laboratory of Molecular Engineering of Polymers,Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials,Fudan University,Shanghai 200433,China%Department of Chemistry,College of Science,King Saud University,PO Box 2455,Riyadh 11451,Saudi Arabia; Department of Chemistry,State Key Laboratory of Molecular Engineering of Polymers,Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials,Fudan University,Shanghai 200433,China
• Subjects: Core-shell; Fe3O4@carbon; Interfacial polymerization; Magnetic microspheres; Recyclability; Solid acid catalyst; Sulfonic acid-functionalization; Fe3O4@carbon; Sulfonic acid-functionalization; Recyclability; Magnetic microspheres; Interfacial polymerization; Solid acid catalyst; Core-shell
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2020.11.027

Sulfonic acid-functionalized core-shell Fe3O4@carbon microspheres (Fe3O4@C-SO3H) are rationally synthesized and utilized as the magnetically recyclable solid acid catalysts for the acetalization reaction between benzaldehyde and ethylene glycol with a high selectivity to benzaldehyde glycol acetal (97%) and good recyclability. [Display omitted] Green and recyclable solid acid catalysts are in urgent demand as a substitute for conventional liquid mineral acids. In this work, a series of novel sulfonic acid-functionalized core-shell Fe3O4@carbon microspheres (Fe3O4@C-SO3H) have been designed and synthesized as an efficient and recyclable heterogeneous acid catalyst. For the synthesis, core-shell Fe3O4@RF (resorcinol-formaldehyde) microspheres with tunable shell thickness were achieved by interfacial polymerization on magnetic Fe3O4 microspheres. After high-temperature carbonization, the microspheres were eventually treated by surface sulfonation, resulting in Fe3O4@C-x-SO3H (x stands for carbonization temperature) microspheres with abundant surface SO3H groups. The obtained microspheres possess uniform core-shell structure, partially-graphitized carbon skeletons, superparamagnetic property, high magnetization saturation value of 10.6 emu/g, and rich SO3H groups. The surface acid amounts can be adjusted in the range of 0.59–1.04 mmol/g via sulfonation treatment of carbon shells with different graphitization degrees. The magnetic Fe3O4@C-x-SO3H microspheres were utilized as a solid acid catalyst for the acetalization reaction between benzaldehyde and ethylene glycol, demonstrating high selectivity (97%) to benzaldehyde ethylene glycol acetal. More importantly, by applying an external magnetic field, the catalysts can be easily separated from the heterogeneous reaction solutions, which later show well preserved catalytic activity even after 9 cycles, revealing good recyclability and high stability.