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

该项目的目标是利用mof的模块化结构原理来合成新的、水解稳定的框架结构，这些框架结构具有气体分子可接近的大空隙。作为一个合理的概念，将遵循两个策略：a)提高连接体金属键强度；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三氟甲基等疏水基团修饰。总的来说，这项研究不仅涉及合成和结构研究，而且还涉及了解与水-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，将采用不同的策略：Bharadwaj教授（印度）的研究小组将在羧酸盐之外使用具有吡啶或咪唑等供体基的配体，以提高mof中的连接剂-金属键的强度。此外，将测试疏水性基团（如CF3）的引入，一方面创建疏水，拒水表面，另一方面增强对疏水分子（碳氢化合物，氢）的吸附能力。德国团队将专注于合成介孔zr基mof，并结合疏水单羧酸的引入，发挥簇保护屏蔽的作用。另一方面，在高压储气库中，介孔是实现高储气容量的必要条件。Kaskel教授小组将对两个工作组制备的mof的吸附性能进行研究，并系统研究加入官能团对吸附性能和等压吸附头的影响。战略目标：鉴定水解稳定的mof；表面疏水性的控制；提高水解稳定性；不同疏/亲水性mof表面的水吸附机理连接体化学：除羧酸基外，还含有吡啶或咪唑等给体基团的连接体的设计和合成策略；疏水官能团在mof中的整合模块化连接器概念，用于系统地剪裁特定的相互作用。合成方法及结构分析：新型连接剂在稳定多孔网络中的集成单晶的合成；单晶x射线结构分析；气体吸附实验的放大。孔隙度和表征：溶液（染料吸附）和气相（77K氮气）的吸附技术，以证明孔隙的可及性；水蒸气吸附实验研究mof的疏水性。功能：不同气体（H2、CO2、CH4、Kr）的高压储气库；气体分离（选择性气体吸附）；正丁烷吸附实验证明了对疏水性物质的吸附能力。

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.