Fabrication of Ruthenium Nanoparticles in Porous Organic Polymers: Towards Advanced Heterogeneous Catalytic Nanoreactors

• Published in: Chemistry : a European journal 2015-12, Vol.21 (52), p.19016-19027
• Main Authors: Mondal, John, Kundu, Sudipta K., Hung Ng, Wilson Kwok, Singuru, Ramana, Borah, Parijat, Hirao, Hajime, Zhao, Yanli, Bhaumik, Asim
• Format: Article
• Language: English
• Subjects: Alkylation; Benzene; Catalysis; Catalysts; Catalytic activity; Catalytic converters; Chemistry; Copolymers; Cross polarization; density functional calculations; Dimethyl acetals; Dispersion; Ethylene glycol; Fabrication; Ferric chloride; heterogeneous catalysis; Hydrocarbons; Hydrogenation; Iron chlorides; Magnetic resonance spectroscopy; Materials selection; Mathematical analysis; Nanoparticles; Nanostructure; Nitrobenzene; NMR; NMR spectroscopy; Nuclear magnetic resonance; Oxidation; Pathways; Photoelectron spectroscopy; Photoelectrons; Polymers; Reaction time; Recyclability; Ruthenium; Selectivity; Silicon dioxide; Spectroscopy; Spectrum analysis; Spinning (materials); Titanium dioxide; Valence; X-rays
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201504055

A novel strategy has been adopted for the construction of a copolymer of benzene–benzylamine‐1 (BBA‐1), which is a porous organic polymer (POP) with a high BET surface area, through Friedel–Crafts alkylation of benzylamine and benzene by using formaldehyde dimethyl acetal as a cross‐linker and anhydrous FeCl3 as a promoter. Ruthenium nanoparticles (Ru NPs) were successfully distributed in the interior cavities of polymers through NaBH4, ethylene glycol, and hydrothermal reduction routes, which delivered Ru‐A, Ru‐B, and Ru‐C materials, respectively, and avoided aggregation of metal NPs. Homogeneous dispersion, the nanoconfinement effect of the polymer, and the oxidation state of Ru NPs were verified by employing TEM, energy‐dispersive X‐ray spectroscopy mapping, cross polarization magic‐angle spinning 13C NMR spectroscopy, and X‐ray photoelectron spectroscopy analytical tools. These three new Ru‐based POP materials exhibited excellent catalytic performance in the hydrogenation of nitroarenes at RT (with a reaction time of only ≈30 min), with high conversion, selectivity, stability, and recyclability for several catalytic cycles, compared with other traditional materials, such as Ru@C, Ru@SiO2, and Ru@TiO2, but no clear agglomeration or loss of catalytic activity was observed. The high catalytic performance of the ruthenium‐based POP materials is due to the synergetic effect of nanoconfinement and electron donation offered by the 3D POP network. DFT calculations showed that hydrogenation of nitrobenzene over the Ru (0001) catalyst surface through a direct reaction pathway is more favorable than that through an indirect reaction pathway. This way or that? A strategy has been adopted to develop a benzene–benzylamine‐1 (BBA‐1) porous organic polymer (POP) by Friedel–Crafts alkylation. Ru@POP behaves as a heterogeneous catalytic nanoreactor for the catalytic transfer hydrogenation of nitroarenes at RT through a direct reaction pathway, as supported by DFT computational calculations (see figure).