【作者】 潘建国；

【导师】 赵玉来； 侯琳熙；

【作者基本信息】 福州大学 ， 化学工程（专业学位）， 2021， 硕士

【摘要】 在温室效应日益严重的今天,CO₂资源化利用日益得到重视。目前,CO₂环加成反应是最有前景的CO₂固定方法之一。但由于CO₂的高稳定性,使得环加成反应发生条件极为苛刻,因此开发出一种能够低温低压下催化CO₂环加成反应的催化剂是极具意义且充满挑战性的课题。席夫碱金属配合物与金属-有机框架材料（MOFs）通常作为催化剂应用于CO₂环加成反应体系。席夫碱金属配合物可在较为温和的条件下表现出良好的催化活性,但存在产物不易分离的问题。而MOFs由于具有较大的比表面积并且基团可修饰,在CO₂环加成反应体系中表现出优异的催化活性,但需在高温高压下才能使反应发生。基于上述情况,本论文采用两种不同策略得到双金属席夫碱/MOFs多孔材料,并将其应用于CO₂环加成反应体系。主要研究内容包括以下两个部分:（1）利用NH₂-UiO-66的大框架结构,令席夫碱配体与过渡金属在MOFs框架内进行络合,得到系列Salen（M）-UiO-66（X）多孔材料。首先,对不同席夫碱配体与Co络合得到的Salen（Co）-UiO-66（X）（X:H、F、Cl、Br）进行研究,通过对其进行XRD、FT-IR、XPS表征证明成功将席夫碱金属配合物包覆于MOFs框架内。同时,研究了多孔材料对CO₂环加成反应的催化性能,发现Salen（Co）-UiO-66在无溶剂下催化CO₂与PO环加成反应活性最佳。在上述研究的基础上,制备了不同金属络合的Salen（M）-UiO-66（M:Co、Mo、Ni、Zn）,通过XRD等对其结构进行分析。催化CO₂与PO环加成反应表明,得到的Salen（Ni）-UiO-66在100℃、1.2 MPa下,反应12 h后,PO的转化率达到97.3%,碳酸丙烯酯（PC）的选择性达到90.6%,且多孔材料在循环使用4次后,活性仅有小幅波动。最后,对其催化动力学进行探究,反应活化能E_a=52.65 kJ·mol^-1。（2）利用NH₂-UiO-66上的-NH₂,使得MOFs成为合成席夫碱配体的原料,再将过渡金属与合成的配体结构络合,得到系列Salen（M）@UiO-66（X）多孔材料。首先,研究了不同水杨醛类有机物合成的配体结构与Co配位得到Salen（Co）@UiO-66（X）（X:H、F、Cl、Br）多孔材料,通过XRD、FT-IR、XPS证明氨醛缩合的发生并且过渡金属发生了配位,活性研究表明Salen（Co）@UiO-66在无溶剂条件下催化CO₂与PO环加成反应效果最佳。随后,制备了不同金属络合的Salen（M）@UiO-66（M:Co、Mo、Ni、Zn）进行研究。催化CO₂与PO环加成反应表明,Salen（Mo）@UiO-66在80℃、1.2 MPa,反应6 h后,PO的转化率达到95.1%,PC的选择性达到94.7%,当催化剂循环使用4次后,活性无明显降低,结构无明显变化。进一步的对其催化动力学进行探究,反应活化能显著降低,E_a=17.42 kJ·mol^-1。最后根据上述实验结果,提出可能的反应机理。更多还原

【Abstract】 Nowadays,the greenhouse effect is becoming more and more serious so that the utilization of CO₂ resources is getting more and more attention.At present,the CO₂ cycloaddition reaction is one of the most promising methods for CO₂ fixation.However,the conditions for the cycloaddition reaction are extremely harsh due to the high stability of CO₂.Therefore,developing a catalyst that can catalyze the CO₂ cycloaddition reaction under relatively mild reaction conditions is a significant and challenging subject.Schiff base metal complexes and metal-organic framework materials（MOFs）have their own advantages and disadvantages in the CO₂ cycloaddition reaction.Schiff base metal complexes can exhibit good catalytic activity under relatively mild conditions,but the product is not easy to separate.MOFs exhibit excellent catalytic activity in the CO₂ cycloaddition reaction system due to their large specific surface areas and modifiable groups,but they require high temperature and high pressure to make the reaction occur.Based on the above situations,this thesis uses two different strategies to obtain Schiff base/MOFs porous composites and apply them to the CO₂ cycloaddition reaction system.The main research contents include the following two parts:（1）The Schiff base ligand and transition metal are complexed by using the large framework structure of NH₂-UiO-66 in the framework of MOFs to obtain a series of Salen（M）-UiO-66（X）porous materials.Firstly,the Salen（Co）-UiO-66（X）（X:H,F,Cl,Br）obtained by the complexation of different Schiff base ligands with Co was studied,and XRD,FT-IR,and XPS characterization proved that Schiff base metal complexes were successfully coated in the framework of MOFs.At the same time,the catalytic performance of the porous material on the CO₂ cycloaddition reaction was studied,and it was found that Salen（Co）-UiO-66 had the best activity in catalyzing the cycloaddition reaction of CO₂ and PO without solvent.On the basis of the above research,Salen（M）-UiO-66（M:Co,Mo,Ni,Zn）complexed with different metals was prepared,and its structure was analyzed by XRD.The catalyzed cycloaddition reaction of CO₂ and PO showed that the conversion rate of PO reached 97.3%and the selectivity of propylene carbonate（PC）reached90.6%after that the obtained Salen（Ni）-UiO-66 was reacted for 12 h at 100℃and 1.2 MPa.And the activity of the porous material only fluctuates slightly after being recycled for 4 times.Finally,the catalytic kinetics was explored,and the reaction activation energy（E_a）was 52.65 kJ·mol^-1.（2）The-NH₂ on NH₂-UiO-66 was innovatively used and made the MOFs become the raw material for the synthesis of Schiff base ligands,and then complexes the transition metal with the synthesized ligand to obtain a series of Salen（M）@UiO-66（X）porous material.Firstly,the Salen（Co）@UiO-66（X）（X:H,F,Cl,Br）porous materials obtained by coordination reaction of the ligands synthesized by different salicylaldehyde organic compounds and Co were studied.The results of XRD,FT-IR and XPS proved that ammonia aldehyde condensation occurred and the transition metal was coordinated.Activity studies showed that Salen（Co）@UiO-66 had the best effect in catalyzing the cycloaddition reaction of CO₂ and PO under solvent-free conditions.Subsequently,Salen（M）@UiO-66（M:Co,Mo,Ni,Zn）complexed with different metals was prepared for research.The cycloaddition reaction of catalyzing CO₂ and PO showed that the conversion rate of PO reached 95.1%,and the selectivity of PC reached 94.7%in the presence of Salen（Mo）@UiO-66 at 80℃and 1.2 MPa for 6 h.When the catalyst is recycled for 4 times,there was no significant decrease in activity and no significant change in structure.Further investigation of its catalytic kinetics found that the activation energy of the reaction was significantly reduced,and the reaction activation energy（E_a）was 17.42 kJ·mol^-1.Finally,a possible reaction mechanism is proposed based on the above experimental results.更多还原