Department of Chemistry, University of Crete, Voutes Campus, GR-71003 Heraklion, Greece.
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, GR-11635 Athens, Greece.
Molecules. 2022 Apr 19;27(9):2614. doi: 10.3390/molecules27092614.
Water adsorption in metal-organic frameworks has gained a lot of scientific attention recently due to the potential to be used in adsorption-based water capture. Functionalization of their organic linkers can tune water adsorption properties by increasing the hydrophilicity, thus altering the shape of the water adsorption isotherms and the overall water uptake. In this work, a large set of functional groups is screened for their interaction with water using ab initio calculations. The functional groups with the highest water affinities form two hydrogen bonds with the water molecule, acting as H-bond donor and H-bond acceptor simultaneously. Notably, the highest binding energy was calculated to be -12.7 Kcal/mol for the -OSOH group at the RI-MP2/def2-TZVPP-level of theory, which is three times larger than the reference value. Subsequently, the effect of the functionalization strategy on the water uptake is examined on a selected set of functionalized MOF-74-III by performing Monte Carlo simulations. It was found that the specific groups can increase the hydrophilicity of the MOF and enhance the water uptake with respect to the parent MOF-74-III for relative humidity (RH) values up to 30%. The saturation water uptake exceeded 800 cm/cm for all candidates, classifying them among the top performing materials for water harvesting.
由于在基于吸附的水捕获中具有潜在应用，金属有机骨架（MOFs）中的水吸附最近引起了广泛的科学关注。通过增加亲水性，可以对其有机连接体进行功能化来调节水吸附性能，从而改变水吸附等温线的形状和总吸水量。在这项工作中，使用从头算计算方法对大量功能基团进行了筛选，以研究其与水的相互作用。与水亲和力最高的功能基团与水分子形成两个氢键，同时充当氢键供体和氢键受体。值得注意的是，在 RI-MP2/def2-TZVPP 理论水平下，-OSOH 基团的结合能最高可达-12.7 Kcal/mol，是参考值的三倍。随后，通过进行蒙特卡罗模拟，在选定的一组功能化 MOF-74-III 上研究了功能化策略对水吸收的影响。结果发现，对于相对湿度（RH）值高达 30%的情况，特定基团可以提高 MOF 的亲水性，并相对于母体 MOF-74-III 增强水的吸收。所有候选物的饱和水吸收量均超过 800 cm/cm，将它们归类为用于水收集的性能最佳材料之一。
