Pt/Al2O3 coated with N-doped carbon as a highly selective and stable catalyst for catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline

Platinum clusters anchored on sulfur-doped ordered mesoporous carbon for chemoselective hydrogenation of halogenated nitroarenes

Chemoselective hydrogenation of unsaturated organic compounds is a significant research topic in the catalysis field. Herein, a sulfur-doped ordered mesoporous carbon (SMC) material was prepared to anchor ultrafine platinum (Pt) clusters for the chemoselective hydrogenation of halogenated nitroarenes. The confinement effect of the ordered pores and the strong metal-support interaction caused by Pt clusters and sulfur atoms, efficiently suppress the aggregation and regulate the electronic states of the ultrafine Pt clusters. Thus, the hydrogenation of parachloronitrobenzene (p-CNB) shows high selectivity catalyzed by the ultrafine Pt clusters with electron-rich states. Meanwhile, the catalytic performance of the hydrogenation reaction catalyzed by Pt/SMC is capable of being maintained after at least 5 cycles, and the catalytic universality can also be applied to different halogenated nitroarenes hydrogenation. Therefore, this study may promote the research into the construction of noble metal-based catalysts for chemoselective hydrogenation reactions in green and sustainable chemical processes.

Carbon Deposition on Heterogeneous Pt Catalysts Promotes the Selective Hydrogenation of Halogenated Nitroaromatics

Pt-based heterogeneous metal catalysts are commonly used in the hydrogenation of nitro groups. However, the continuous large metal domain size and the complex interaction between the substrates and metal surface usually inevitably result in side reactions, such as dehalogenation of halogenated nitroaromatics. In this work, by simply treating the Pt-based catalysts with CO at elevated temperature, the Boudouard reaction taking place on Pt surface results in the deposition of carbon species thereon. The carbon deposition not only inhibits the dehalogenation by restricting the planar interaction of the aromatic group with the Pt surface that is segmented by C, the hydrogenation activity of the nitro group is also enhanced on the partially positively charged surface Pt sites created by the electron-withdrawing interstitial C. Such a simple treatment strategy is effective for fabricating Pt-based catalysts on different supports toward the selective hydrogenation of a wide range of halogenated nitroaromatics.

Pt nanoparticles on Ti3C2Tx-based MXenes as efficient catalysts for the selective hydrogenation of nitroaromatic compounds to amines

The development of Pt nanocatalysts for the selective hydrogenation of nitroaromatic compounds to the corresponding amines is of great significance to solve the drawbacks associated with a low reserve of Pt. Herein, we develop a protocol for the preparation of a Pt/titanium carbide-based MXene heterostructure for the selective reduction of nitroaromatic compounds. In the heterostructure, well-defined and nano-sized metallic Pt crystallites are uniformly decorated on Ti3C2Tx nanosheets using a mild reducing agent of ammonia borane without additional stabilizing agents. The selective hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN) was employed as a model reaction to investigate the catalytic performance of the as-synthesized heterostructure, denoted as Pt/Ti3C2Tx-D-AB. Notably, this catalyst can catalyze the complete conversion of p-CNB to p-CAN with 99.5% selectivity, superior to that of Pt/Ti3C2Tx-D-SB synthesized with sodium borohydride. The high performance of the present catalytic system can be ascribed to the well-dispersed Pt nanoparticles, the abundant surface electron-efficient Pt(0), and the synergistic catalysis between Pt/Ti3C2Tx-D-AB and water. This catalyst also shows generality toward the selective hydrogenation of a series of nitroaromatic compounds to the corresponding amines with high efficiency. The present study provides a strategy to synthesize efficient catalysts for catalytic applications.