Preparation And Catalytic Performance Of Heteroatom Doped Controllable Pore Regulating Materials

Heteroatom-doped hierarchically porous materials have been widely used in adsorption and separation technology,heterogeneous catalysis,energy storage,sensing and so on.In recent years,the study of embedding different types of heteroatoms in porous materials has become a focus for scholars.Typically,precursors containing different heteroatoms can be incorporated into the porous material skeleton through carbonization or chemical post-modification of hierarchically porous materials.Therefore,the selection of post-modification groups and carbon precursors is crucial for the rational design of porous materials with specific applications and maximum function.Based on the chemical post-modification method,the silane agents with different types of heteroatomic functional groups were reacted with the free silanol groups on the surface of SBA-15 and thereby were grafted on the surface of this support.Nitrogen and sulfur atoms were successfully doped on the mesoporous Si O₂ surface.At the same time,mesoporous silica materials with different pore structures were synthesized by changing the preparation conditions of template agents and adding different amounts of pore-expanding agents.These prepared catalysts were evaluated for the selective catalytic hydrogenation of benzoic acid,and it was found that Ru/SBA-15-SH has excellent catalytic performance.It can achieve almost 100%conversion in 80 min under conditions of 100℃and 10 bar H₂ pressure.This is mainly due to the appropriate pore structure of the material,moderate polarity of functionalized thiol groups on the carrier surface,and high Ru⁰/Ru^X+ratio.We proposed a strategy for rapid complete dechlorination by exploiting B,N co-doped hierarchically porous carbon material（BNC）to immobilize Pd NPs,which makes use of not only the micro/meso porous structure to accelerate the mass transport and to provide enormous active sites,but also the synergistic effect for codoping of B,N to enhance interaction between Pd NPs and support and thus to stabilize and disperse the small size of Pd particle.Ascribed to these combined advantages,Pd/BNC exhibited more distinctive catalytic dehalogenation activity(k=-0.14 min^-1)and better stability（about 90.0%activity retention after 5 cycles）than Pd/C(k=-0.0070 min^-1).Additionally,Density functional theory（DFT）calculation indicates that the incorporation of N and B atoms in the carbon skeleton will reduce the adsorption energy of Cl^-and thus Pd/BNC exhibits more remarkable stability than Pd/C during long-term HDC reaction.Continuing the design concept of heteroatomic precursor,the 3-amino-5-thiol-1,2,4-triazole materials containing nitrogen and sulfur atoms were used to synthesize palladium-based hierarchically porous nitrogen and sulfur（Pd/SNC-1.5）catalyst by soft template method.To explore the synergistic effect of nitrogen and sulfur co-doping,hierarchically pore carbon materials with no doping,N atom single doping and different doping amounts were prepared.In this part,hydrodechlorination of chlorophenol was used as the research object to evaluate these prepared catalysts.Compared to Pd/C(k=-0.00489 min^-1,E_a=48.6 k J/mol),the optimized Pd/SNC-1.5(k=-0.23 min^-1,E_a=18.3 k J/mol)has higher catalytic activity and still maintains high catalytic activity after five cycles of reaction.Through detailed analysis of characterization results and experimental data,we confirmed that the high catalytic activity of Pd/SNC-1.5 is mainly related to the high specific surface area of the carrier,regular pore structure,rich sulfur and nitrogen active sites and the synergistic effect of forming catalytically active defects within its framework.Among them,the abundant in-plane pores and the regular hierarchically pore structure can provide an efficient mass transfer path,while the sulfur and nitrogen atoms in the lattice can produce a co-doping effect to regulate the electrons in the carbon skeleton,and produce deep skeleton defects to make the material have more dispersed active sites.All the results show that the prepared Pd/SNC-1.5 is a catalyst with a wide influence on the hydrodechlorination of chlorophenol.This heterogeneous catalyst achieves the purpose of optimizing catalytic performance by reasonably adjusting the chemical microenvironment around the active site.This catalyst design concept can be extended to other types of catalyst preparation.