Synthesis of hydrolytically stable metal-organic frameworks by control of inner surface hydrophobicity

拟议项目的目标是利用MOF的模块化构建原理来合成新的、具有较大空隙的、可被气体分子访问的水解性稳定的骨架结构。作为一个合理的概念，将遵循两个策略：a)增强连接体金属键强度b)合成具有疏水内表面的MOF为了达到这些目标，这些材料中的空隙将被装饰上疏水基团，如三氟甲基。总体而言，这项研究不仅包括合成和结构研究，还包括了解与水-固反应有关的水吸附的基本方面。为了提高MOF的水解稳定性，将遵循不同的策略：Bharadwaj教授(印度)的小组将使用带有给体基团的配体，如吡啶或咪唑，以及羧酸盐，以增强MOF中的连接体-金属键强度。此外，还将测试疏水基团(如CF3)的引入，一方面创建疏水、憎水的表面，另一方面增强对疏水分子(碳氢、氢)的吸附能力。德国集团将专注于合成介孔锆基MOF，并引入疏水一元酸，这应该会起到团簇保护的作用。另一方面，在高压储气库中，要实现高储气量，需要介孔材料。Kaskel教授组将对两个工作组制备的MOF的吸附性能进行研究，并系统研究引入的官能团对吸附性能和等量吸附头部的影响。主要科学目标：战略目标：确定具有水解性稳定的MOF；控制表面疏水性；提高水解性稳定性；不同疏水/亲水表面的MOF的水吸附机理。连接物化学：除了羧酸基以外还含有吡啶或咪唑等给体基团的连接物的设计和合成策略；将疏水官能团整合到MOF中；用于系统调整特定相互作用的模块化连接物概念。合成方法和结构分析：将新连接物整合到稳定的多孔网络中；单晶合成；单晶X射线结构分析；气体吸附实验的放大。孔隙性和表征：溶液(染料吸附)和气相(77K氮气)中的吸附技术，以证明孔的可达性；水蒸气吸附实验用于研究MOF的疏水程度。功能：对不同气体(H2、CO2、CH4、Kr)进行高压储气；气体分离(选择性气体吸附)；正丁烷吸附实验，证明对疏水物种的吸附能力。

The goal of the proposed project is to use the modular construction principles of MOFs for the synthesis of new, hydrolytically stable framework structures with large empty spaces that are accessible to gas molecules. As a rational concept two strategies will be followed: a) enhancing linker metal bond strengthsb) synthesis of MOFs with hydrophobic inner surface To reach these goals the voids in these materials will be decorated with hydrophobic groups such as trifluoromethyl. Overall, the research involves not only the synthesis and structural studies, but also a quest to understand the fundamental aspects of water adsorption in relation to water-solid reactions.To enhance the hydrolytic stability of MOFs, different strategies will be followed: the group of Prof. Bharadwaj (India) will use ligands with donor groups like pyridine or imidazole in addition to carboxylate, to enhance the linker-metal bond strength in MOFs. Additionally, the introduction of hydrophobic groups (such as CF3) will be tested, to create the hydrophobic, water-repellent surface on the one hand, and to enhance the adsorption capability for hydrophobic molecules (hydrocarbons, hydrogen) on the other hand. The German group will focus on the synthesis of mesoporous Zr-based MOFs in combination with introduction of hydrophobic monocarboxylic acids, which should play a role of cluster protecting shields. The mesoporosity on the other hand is needed to achieve the high storage capacity in high pressure gas storage. Investigation of adsorption properties of MOFs prepared in both working groups, as well as systematic study of influence of incorporated functional groups on adsorption properties and isosteric head of adsorption will be performed in the group of Prof. Kaskel.Key scientific goals:Strategic goals:Identification of hydrolytically stable MOFs;Control of surface hydrophobicity;Enhancement of hydrolytic stability;Water adsorption mechanisms on MOFs with different hydrophobic/hydrophilic surface. Linker chemistry:Design and synthesis strategy for linkers bearing donor groups like pyridine or imidazole in addition to carboxylate groups;Integration of hydrophobic functional groups into MOFs; Modular linker concepts for systematic tailoring of specific interactions.Synthesis methods and structure analysis:Integration of new linkers into stable porous networks;Synthesis of single crystals;Single crystal X-ray structural analysis; Up-scaling for gas adsorption experiments.Porosity and Characterization:Adsorption techniques in solution (dye adsorption) and gas phase (nitrogen at 77K) to prove pore accessibility; Water vapor adsorption experiments for study of hydrophobicity degree of MOFs.Functions:High pressure gas storage for different gases (H2, CO2, CH4, Kr); Gas separation (selective gas adsorption);n-Butane adsorption experiments to prove the adsorption ability for hydrophobic species.