【作者】 张岩；

【导师】 付昱；

【作者基本信息】 东北大学 ， 化学， 2022， 硕士

【摘要】 金属有机骨架(MOF)是一类由无机金属中心(金属离子或金属簇)与有机配体配位形成的一类多孔配位聚合物。由于其多种多样的拓扑结构、较大的比表面积和丰富的金属活性中心等优异的性质,因此在传感、吸附、催化、气体存储和分离、生物医药等领域呈现出巨大的发展潜力和诱人的发展前景,近年来吸引了诸多研究者的兴趣。CuBDC(BDC=对苯二甲酸)作为铜基羧酸类MOF中一类经典的MOF,由于其结构和功能的高度可调性、温和的制备条件以及活性中心和官能团易于修饰等优点而备受关注。作为当前的研究热点,尽管针对CuBDC的研究已取得了一定的进展,但是仍然有诸多挑战亟需解决,比如对其形貌和结构的精准控制的研究还不够深入。因此,本论文选取CuBDC作为研究对象开展了以下研究工作:首先,利用简便的滴加法成功合成了铜基MOF(CuBDC纳米片)。随后,将CuBDC纳米片分别浸泡于pH值梯度变化的醋酸水溶液中,通过一系列详细的表征证实了合适的酸度值会促使MOF晶体发生溶解然后重结晶生成另一种棒状形貌MOF(CuBDC-R),从而实现MOF形貌和结构的转变。利用一系列表征手段对这两种MOF的组分、结构、形貌及MOF转变过程进行了详细的研究,表征结果显示转变后的CuBDC-R的配位形式发生了改变,CuBDC-R会在CuBDC配位形式的基础上脱去DMF(N,N-二甲基甲酰胺)分子,这导致CuBDC-R表现出不同的形貌和结构。当扩展至ZnBDC体系,同样采用滴加的方法,但仅通过改变金属离子和有机配体的相对含量,成功制备出两种形貌和结构不同的ZnBDC。一种是具有海绵状的MOF-5晶体结构,另一种晶体结构与之类似,形貌为片状。通过一系列表征手段发现两种ZnBDC仅仅是框架结构发生了细微改变,而配位的分子种类保持不变,这种方法实现了 MOF结构和形貌的精准控制。此外,在CO2环加成领域,催化实验结果揭示了这两种铜基MOF之间形貌与性能的关系,相较于棒状CuBDC-R,CuBDC纳米片显示出更佳的催化性能,这是因为纳米片形貌更小的尺寸和二维结构拥有更多的催化活性位点所致。这项工作对MOF精准调控、MOF制备及其CO2转化利用领域提供了一定的思路。更多还原

【Abstract】 Metal-organic framework(MOF)are a class of porous coordination polymers composed of inorganic metal centers and organic ligands.Owing to their excellent properties of diverse topological structure,high specific surface area and abundant metal active centers,therefore MOF show great development potential and attractive prospects in the fields of sensing,adsorption,catalysis,gas storage and separation,biomedicine and so on.In recent years,they have caught the eye of many researchers.CuBDC(BDC=terephthalic acid)as a class of classical MOF among copper-based carboxylic acid MOF,have attracted much attention due to their highly tunable structure and function,mild preparation condition,easily adjustable active centers and functional groups.As current research hotspot,although the research on CuBDC has made some progress,there are still many great challenges to be solved.For example,the precise control of their morphology and structure is not enough.Therefore,CuBDC is choosed as the research object to carry out the following research work in this paper.First,the Cu-based MOF(CuBDC nanosheets)is successfully synthesized by simple distribution droplets method.Subsequently,CuBDC nanosheets are immersed into acetic aqueous solution with pH gradient respectively.A series of detailed characterizations confirm that the appropriate acidity promotes the dissolution of MOF crystal and then recrystallize to form another rod-shaped MOF(CuBDC-R),thereby achieving the transformation of MOF morphology and structure.The composition,structure,morphology and the transformation process of MOF are studied in detail by a series of characterizations,the characterization results show that the coordination form of the transformed CuBDC-R has changed,CuBDC-R remove the DMF(N,N-dimethylformamide)molecule compared with the coordination form of CuBDC.When extend to the ZnBDC system,the distribution droplets method continue to be adopted,only by changing the relative content of metal ions and organic ligands,two ZnBDC with different morphology and structures are successfully prepared.One has spongy crystal structure of MOF-5,the other one has similar crystal structure with sheet-like morphology.Through a series of characterization methods,it is found that only the framework structure of two ZnBDC have changed slightly,while the coordination molecular species remain unchanged.This method achieves precise control of the structure and morphology of MOF.In addition,in the field of CO2 cycloaddition,catalytic results reveal the relationship between the morphology and catalytic performance of two Cu-based MOF.Compared with rod-shaped CuBDC-R,CuBDC nanosheets show better catalytic performance owing to the smaller size and two-dimensional structure of nanosheets having more catalytic active sites.This work provides some ideas for the fields of precise regulation of MOF,preparation of MOF and CO2 conversion and utilization.更多还原