MOFs (metal-organic frameworks) based on fluorinated and perfluorinated aromatic carboxylate ligands: directed synthesis, structures, and properties

金属有机骨架和配位聚合物是现代固体化学和材料化学的研究热点。最近，人们试图通过引入部分和全氟连接配体来优化这些化合物的气体存储和分离性能。此外，在热稳定性和化学稳定性方面，这些改性材料有望具有更好的性能。然而，文献中的文献，无论这是否真的成功，都是相互矛盾的，因为只有少数几个不同氟化程度的同构MOF可以进行比较研究。我们提出了一个基于简单结构参数的概念，即羧酸基和苯环之间的扭转角，这使得选择性地合成具有不同氟化程度的芳香羧酸配体的同构MOF成为可能。对合成的MOF进行化学稳定性、热稳定性以及对不同极性和非极性气体的气体吸附性能的比较研究。特别是，由于配体的氟化，MOF孔内的极性变化是重要的。开发了一个简单的实验，它允许通过在MOF孔中掺入溶致变色染料来确定极性变化。这些结果应与接触角的测量相关联，以确定各自MOF的疏水性和理论计算(合作中)。

MOFs (metal-organic frameworks) and coordination polymers (CPs) are an intensely studied research area of modern solid state and materials chemistry. Recently, attempts have been made to optimize the gas storage and separation properties of these compounds by incorporating partial and perfluorinated linker ligands. Also in terms of thermal and chemical stability, these modified materials are expected to have improved properties. However, the references in the literature, whether this is actually successful, are contradictory, since there are only few isostructural MOFs with different degrees of fluorination at which comparative investigations can be carried out.We present a concept based on a simple structural parameter, namely the torsion angle between the carboxylate group and the phenyl ring, which makes it possible to selectively prepare isostructural MOFs with aromatic carboxylate ligands with different degrees of fluorination. Comparative investigations on the chemical and thermal stability as well as the gas adsorption properties for different polar and non-polar gases shall be carried out on these MOFs thus synthesized. In particular, the changed polarity within the MOF pore is important due to the fluorination of the ligand. A simple experiment was developed, which allows the polarity changes to be determined by the incorporation of a solvatochromic dye into the MOF pores. These results shall be correlated with measurements of the contact angle to determine the hydrophobicity of the respective MOFs and theoretical calculations (in cooperation).