The Preparation Of Nitrogen-doped Porous Carbon Based Catalyst And Their Catalytic Performance

In recent years,with the increasingly concerns of environmental and health problems,the treatment of nitro-containing aromatic compounds in pyrotechnic wastewater has get more and more attention.The reported methods include adsorption,coagulation,precipitation,extraction,neutralization,and electrolysis.Using catalytic reduction treatment can not only reduce pollution,but also obtain value-added chemical substances,such as nitroso benzene,azobenzene oxide,azobenzene,hydrogenated azobenzene,and aromatic amine.One of the typical methods is the selective reduction of nitroaromatics by the supported metal nanoparticles.It should be mentioned that the activity and selectivity are inevitably tied to the nature of the supports.Nitrogen-doped porous carbon are one of the promising supports because of their high porosity,small density,large surface area,acid-proof alkaline and good conductivity.In this case,a series nitrogen-doped porous carbon based catalysts were successfully synthesized and used in nitrobenzene reduction.The main contents are as follows:1)Metal nanoparticles?NPs?supported on nitrogen-doped porous carbon?NPC?are one type of promising heterogeneous catalysts,the tuning and understanding of the metal-support interactions are crucial for the design and synthesis of highly durable and efficient heterogeneous catalytic systems.We present an effective strategy to integrate ultrafine metal NPs into NPC through utilizing covalent organic gel?COG?as the precursor for the first time.The ruthenium?Ru?NPs are uniformly dispersed in NPCs with the average size as low as1.90±0.4nm.Irrespective of ultrafine size,the Ru NPs show unprecedented stability and recyclability in Ru-catalyzed reduction of nitrobenzene,which are greatly superior to commercial Ru/C and NPC-supported Ru NPs synthesized by traditional post-loading method.This synthetic strategy can be extended to the synthesis of other metal or alloy NPs for a variety of advanced applications.2)Hollow carbon materials with versatile chemical compositions and complicated shell architectures hold great promises in heterogeneous catalysis,it is a daunting challenge to synthesize metal alloy NPs supported by the hollow nanostructures.Herein,we present a simple approach for facile fabrication of Pd-Cu alloy NPs embedded in hollow octahedral N-doped porous carbon?Pd-Cu@HO-NPC?.The hollow material is derived from HKUST-1coated by imidazolium-based ionic polymer?ImIP?.Water-sensitive HKUST-1 is simultaneously removed in the process of anion exchange between bromide in the ImIP shell and tetrachloropalladate in aqueous medium.The released Cu?II?ions and exchanged Pd?II?ions serve as Cu and Pd sources in subsequent pyrolysis.The resultant Pd-Cu@HO-NPC exhibits high catalytic activity,selectivity,stability and recyclability in the reduction of nitrobenzene.More attractively,the synthetic strategy is of excellent generality,and could be extended to the synthesis of Cu-based bimetallic and trimetallic alloy NPs,such as Pt-Cu@HO-NPC and Pd-Pt-Cu@HO-NPC.This work highlights the superiority of water-sensitive metal-organic frameworks in the ingenious design of hollow carbon materials incorporated with well-dispersed metal alloy NPs.3)Metal/semiconductor systems are one type of promising heterogeneous photocatalysts for solar conversion.The injection of hot electrons from photoactivated metals to semiconductors is a rate-determining step owing to Schottky barrier created at the interface.It is highly desirable to develop new approaches for promoting hot electron transfer.Herein,we present one type of new Mott-Schottky-type photocatalytic materials consisting of TiO₂nanosheets and Ru NPs encapsulated by nitrogen-doped carbon?TiO₂@NC-Ru-T?.They are readily available through the conformal encapsulation of TiO₂ by main-chain imidazolium-based ionic polymer?ImIP?,followed by anion exchange with perruthenate and subsequent pyrolysis,the sintering of Ru NPs is effectively inhibited by ImIP,generating small-size and well-dispersed Ru NPs.The nitrogen-doped carbon in TiO₂@NC-Ru-T both strengthens the performance of Ru NPs and facilitates photoelectron transfer from photoactivated Ru NPs to TiO₂ through Mott-Schottky contact.The dyadic effects greatly promote selective the reduction of nitrobenzene under visible light irradiation.This work provides a feasible protocol for improving visible light absorption and charge/electron transfer in the photocatalytic reactions,and holds great promises for developing new type of soalr-to-chemical energy conversion reactions.