Preparation And Catalytic Properties Of Heteroatom-Doped Porous Material

Porous materials, including metal–organic frameworks?MOFs?, Covalent organic framework?COFs? and mesoporous carbon, have attracted enormous attention because of their aesthetically pleasing structure and potential applications in adsorption, separation, catalysis, luminescence, magnetism and energy storage. However, pristine porous materials show weak catalytic performance owing to the lack of active centre anchored on the surface. By using of turning sterical and electronic effect of specific surface, a variety of modifications toward the network or surface of porous materials are responsible for enhancing adsorption, diffusion and activating property. In the vein, doping heteroatom into porous materials, which can alter the energy and reactivity of surface, becomes a flexible strategy to enhance chemical activity. Doping nitrogen atom, featuring unique odd-electrons configuration and electronegative trait, effectively promotes the distribution of electronic charge and spin density, inducing catalytically active site in neighboring carbons. Apart from nitrogen atom, sulphur-doping is regarded as an effective approach to alter the property of porous carbons both sterically and electronically because of two pairs of local electrons and larger atomic radius in comparison with C and N atoms. We focus our attention on the synthesis and catalysis of heteroatom-doped porous material?MOFs and mesoporous carbon?.Firstly, we report a new and efficient ionothernal synthesis method for synthesizing a S, N-co-doped mesoporous carbon material through the carbonization of S, N-containing precursors in molten ZnCl₂, where ZnCl2 served as the ionic solvent and Lewis acid catalyst. The resultant SNPC-800 showed a mesoporous structure with a specific surface area of 1235 m2 g-1 and a mesopore-size range of 10–45 nm, which were considerably larger than those obtained through the carbonization of ionic liquids and fabrication of graphene oxides. Furthermore, ORR?oxygen-reduction reaction? measurements indicated good catalytic activity, comparable to the commercial Pt/C catalyst. Also the SNPC-800 material exhibited excellent catalytic stability, and high methanol tolerance compared to the commercial Pt/C catalyst. Density functional theory calculation results revealed that the catalytic properties originated from the synergistic effect of the S/N dopant and that the main catalytic reaction path followed an associative mechanism. LIB?lithium-ion batteries? tests further showed high reversible capacity, as well as excellent cycling stability and rate performance. It is observed that N Play a crucial role in the ORR and LIBs.Secondly,The S-content of S, N-co doped PCs weakens the effect of sulphur atom on electronic and geometric structure of PC, thereby shrinking synergistic role of S and N atoms. We exhibited one facile method to improve the S-content in S, N-co-doped PCs by importing Na H2PO4 into high-temperature carbonation. The obtained S, N, P-co-doped PC? SNPPC? material possess high S and large surface area. Meanwhile, we found high S-content SNPC show outstanding LIBs, ORR and supercapacitors performances than low S content PC. And these differences can be obviously attributed to the enhancing synergistic effects owing to the increase of S content.Thirdly,in order to whether N,S play a crucial role in MOFs catalysis,based on the thoughts, I utilized a series of MOFs included N? such as UiO-67,N-UiO-67, NH2-UiO-67? to load noble metal Pt for the identification whether N atom plays the same role in MOFs catalysis. 5.0% loading Pt nanoparticles support on the UiO-67, N-UiO-67 and NH2-UiO-67, the result indicates that 5.0% Pt/N-UiO-67 had the highest catalytic property for CO oxidation. That was attributed to the size of Pt nanoparticles because of N regulating and controlling. The Pt nanoparticles? NP? were about 2.0 nm, 4.0 nm and 2.0 nm for 5.0% Pt /N-UiO-67,5.0% Pt /UiO-67 and 5.0% Pt /NH2-UiO-67,respectively,which explains the obvious result.To conclude, for the carbon or MOFs material, these N atoms is likely to impart charge density on the C atoms because of the larger difference in the electronegativity between N and C atoms. The resultant charge separation promotes the adsorption of substrates over the catalyst and hence improves the catalysis property. Secondly, these S atoms, featuring two pairs of local electrons and a larger atomic radius?110 pm? than C?70 pm? and N?65 pm? atoms, can easily induce the polarization of neighboring C and N atoms, which increases the catalysis property.