Metallo-aerogels derived from chitosan with encapsulated metal nanoparticles as robust, efficient and selective nanocata
- PDF / 2,103,880 Bytes
- 7 Pages / 612 x 808 pts Page_size
- 63 Downloads / 125 Views
Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, China 2 State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China 3 College of Chemistry and Molecular Engineering, Zhengzhou University, 100 Kexue avenue, Zhengzhou 450001, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 25 March 2020 / Revised: 5 August 2020 / Accepted: 5 August 2020
ABSTRACT A series of robust metallo-aerogels are readily fabricated by pyrolysis of xerogels derived from chitosan-metal (M = Fe, Co, Ni) hydrogels. Owing to the strong coordination between metal ions and the functional groups (NH2 and OH) of chitosan, metallo-aerogels consisting of encapsulated metal-nanoparticles (MNPs) by graphite shells were obtained, as supported by various characterizations including high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), and Raman. The resulting metalloaerogels could be functioned as highly stable, efficient and selective nanocatalysts towards the hydrogenation of nitroarenes to amines at low catalyst loading (1.2 mol.%–2.4 mol.%). Remarkably, the metallo-aerogels could be reused for more than 30 runs without obvious loss of activity and selectivity. These distinguished performances were attributed to the graphitic shells formed during the pyrolysis, which hampered the possible aggregation of MNPs, prevented metal leaching and increased their stability.
KEYWORDS metallo-aerogels, nanocatalysts, nitroarenes, reduction, pyrolysis
1
Introduction
The stability of the metal-nanoparticles (MNPs) is crucial for their catalytic activity. During the reaction process, most of unprotected MNPs readily aggregate together to generate deactivated species or clusters [1, 2]. A number of strategies, including but not limited to dispersing the MNPs with supports like carbon black, carbon nanotubes or graphene, have been conceived to address this problem [3]. However, due to the weak interactions between metal and supports, metal leaching and agglomeration are still inevitable [4, 5]. Moreover, the compacted crust/covering may not only block potential active sites but may also affect the substance transfer [6, 7]. Therefore, how to encapsulate and isolate MNPs in the porous matrixes with unaffected active sites is highly desirable [8, 9]. Consequently, coating strategies of preparing protected MNPs with meso- or microporous oxides [10–12], carbon [13, 14] and polymer [15, 16] shells have also been applied, and among them porous carbon aerogels (CAs) [17–20] may be regarded as promising materials for preparing well-dispersed MNPs owing to their very low density, high porosity and large surface area [17, 18]. Graphene [21–23], carbon nanotube [24, 25] and bacterial-cellulose-derived carbon nanofiber [26, 27] are often used as precursors, followed by post-modification with selected metal anions
Data Loading...
