Highly-active platinum nanoparticle-encapsulated alumina-doped resorcinol–formaldehyde carbon composites for asymmetric hydrogenation

Abstract

Herein, a new type of highly-active platinum (Pt) nanoparticle encapsulated alumina-doped resorcinol–formaldehyde carbon composite (Al@RFC) is fabricated based on resorcinol–formaldehyde (RF) resin and aluminum acetylacetonate using a one-step carbonization approach and evaluated for an asymmetric hydrogenation (AH) reaction. The carbonization process of RF is essentially completed at 700 °C and resulted in Al@RFC with uniform and ordered porous structures. The Pt/Al@RFC catalysts are decorated with uniformly dispersed Pt nanoparticles of around 4 nm diameter over the Al@RFC support. The prepared catalysts are chirally modified with cinchonidine (CD) to explore the catalytic efficiency of AH of ethyl 2-oxo-4-phenylbutanoate (EOPB). The Pt/Al@RFC catalysts have substantially circumvented the shortcomings of poor repeatability of Pt/Al₂O₃ and low ee values of Pt/C catalysts, displaying conversion efficiencies and ee values of 99% and 82%, respectively. Furthermore, the catalyst could be reused 16 times. Notably, the optimized catalyst displayed turn-over frequency (TOF) values of more than 80 000 h⁻¹, which is the highest reported activity in this hydrogenation reaction. Graphene formation during the high temperature (700 °C) carbonization process is proposed to play a role in its exceptionally high activity.