【作者】 张睿；

【导师】 杨照地；

【作者基本信息】 哈尔滨理工大学 ， 化学工程与技术， 2021， 硕士

【摘要】 本文采用基于第一性原理的密度泛函理论,理论设计和构建了二维共价有机框架（2D-COFs）中单层C₄N与单层二硫化钼（Mo S₂）通过范德华力复合的C₄N/Mo S₂异质结和六种新型2D-COFs的微观结构。通过理论计算,对C₄N/Mo S₂范德华异质结和六种新型2D-COFs的可见光光催化能力和反应路径进行深入研究。采用广义梯度近似下的Perdew-Burke-Ernzerhof（PBE）泛函,Grimme色散校正的DFT-D2方法对范德华相互作用校正,研究C₄N/Mo S₂异质结的结构、电子和光学性质。计算分析C₄N/Mo S₂异质结的结构稳定性、能带结构、态密度、电荷密度差和吸收光谱。结构稳定性计算表明单层C₄N和单层Mo S₂在范德华相互作用下可复合形成热力学稳定的异质结结构。电子结构表明在层间范德华相互作用下,C₄N/Mo S₂异质结的能带结构相比于单层C₄N和单层Mo S₂能带结构,带隙减小,C₄N/Mo S₂异质结是Ⅱ型异质结,具有潜在光催化二氧化碳还原和析氧反应能力。静电势和电荷密度差表明C₄N/Mo S₂异质结层间界面处存在内建电场,内建电场驱动光生电荷的有效分离。吸收光谱表明C₄N/Mo S₂异质结相比单层C₄N和单层Mo S₂具有更强的可见光吸收能力。深入的分析揭示C₄N/Mo S₂异质结理论上表现光催化能力,是一种潜在的新型可见光催化剂。设计由1,2,4,5-四取代基（氨基、醛基、硝基）苯和3,5,9,1-四取代基（氨基、醛基、硝基）联苯分别与1,4-对位取代（醛基、氨基）苯缩合形成亚胺键（-C=N-）和偶氮键（-N=N-）连接的6种菱形孔新型2D-COFs结构。采用PBE泛函,计算6种新型2D-COFs的能带结构、态密度、吸收光谱和析氢反应自由能,通过比较筛选出由1,2,4,5-四氨基苯与1,4-对苯甲醛通过亚胺键连接组成的COF-TBI-a具有最强的可见光自发析氢反应能力。通过计算和分析析氢反应自由能变化,揭示其吸收可见光进行析氢的反应机理,为新型光催化剂的设计提供了理论依据。更多还原

【Abstract】 In this thesis,density functional theory（DFT）based on first-principles is used to design and construct the microscopic structures of the C₄N/MoS₂van der Waals heterostructure consisted of two-dimensional covalent organic frameworks（2D-COFs）C₄N monolayer and molybdenum disulfide（MoS₂）monolayer and six novel2D-COFs theoretically.The visible photocatalytic properties of C₄N/MoS₂and six novel 2D-COFs are revealed in depth by theoretical calculations.The structure,electronic structure and optical properties of the C₄N/MoS₂heterostructure were studied by using the Perdew-Burke-Ernzerhof（PBE）of the generalized gradient approximation（GGA）and grimme dispersion correction for van der Waals interaction correction DFT-D2.The calculation for structural stability shows that C₄N monolayer and MoS₂monolayer can be combined to form thermodynamically stable heterojunction structures under van der Waals interaction.The electronic structure proves that the band gap of the C₄N/MoS₂heterostructure is smaller than that of MoS₂monolayer and C₄N monolayer under the interlayer interaction of van der Waals.The C₄N/MoS₂heterostructure is a type-Ⅱheterostructure.It was predicted to show potential photocatalytic activities on carbon dioxide reduction and oxygen evolution reaction.The electrostatic potential and charge density difference show that a built-in electric field exists at the interface,and the built-in electric field drives the effective separation of photogenerated charges.The absorption spectrum indicates that the C₄N/MoS₂heterostructure has strong visible light absorption ability comparing with C₄N monolayer and MoS₂monolayer.The photocatalytic capacity of the C₄N/MoS₂heterostructure is deeply revealed by analysis,which shows that the C₄N/MoS₂heterostructure would be an effective novel visible photocatalyst theoretically.Six rhombohedral pore novel 2D-COFs structures were designed by condensation reaction between 1,2,4,5-tetrasubstituted（amino,aldehyde,nitro）benzene or 3,5,9,1-tetrasubstituted（amino,aldehyde,nitro）biphenyls and 1,4-substituted（aldehyde,amino）benzene to form imine bond（-C=N-）and azo bond（-N=N-）linkages.The band structure,density of state,absorption spectrum and free energy of hydrogen evolution reaction of the 6 novel 2D-COFs were calculated by PBE functional.By comparing study,the COF-TBI-a composed of 1,2,4,5-tetraaminobenzene and 1,4-benzaldehyde through imine bond shows the strongest visible light spontaneous hydrogen evolution reaction ability.The mechanism of photocatalytic hydrogen evolution reaction driven by visible light is revealed by analyzing the free energy change of hydrogen evolution reaction,which provide theoretical basis for the design of novel photocatalysts.更多还原