Frank Hilliary O, Paesani Francesco
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
Materials Science and Engineering, University of California, San Diego, La Jolla, California 92093, USA.
J Chem Phys. 2024 Mar 7;160(9). doi: 10.1063/5.0189569.
Metal-organic frameworks (MOFs), with their unique porous structures and versatile functionality, have emerged as promising materials for the adsorption, separation, and storage of diverse molecular species. In this study, we investigate water adsorption in MOF-808, a prototypical MOF that shares the same secondary building unit (SBU) as UiO-66, and elucidate how differences in topology and connectivity between the two MOFs influence the adsorption mechanism. To this end, molecular dynamics simulations were performed to calculate several thermodynamic and dynamical properties of water in MOF-808 as a function of relative humidity (RH), from the initial adsorption step to full pore filling. At low RH, the μ3-OH groups of the SBUs form hydrogen bonds with the initial water molecules entering the pores, which triggers the filling of these pores before the μ3-OH groups in other pores become engaged in hydrogen bonding with water molecules. Our analyses indicate that the pores of MOF-808 become filled by water sequentially as the RH increases. A similar mechanism has been reported for water adsorption in UiO-66. Despite this similarity, our study highlights distinct thermodynamic properties and framework characteristics that influence the adsorption process differently in MOF-808 and UiO-66.
金属有机框架材料（MOFs）凭借其独特的多孔结构和多样的功能，已成为用于吸附、分离和存储各种分子物种的有前景的材料。在本研究中，我们研究了MOF - 808中的水吸附情况，MOF - 808是一种典型的MOF，它与UiO - 66共享相同的二级结构单元（SBU），并阐明了这两种MOF在拓扑结构和连接性上的差异如何影响吸附机制。为此，我们进行了分子动力学模拟，以计算MOF - 808中作为相对湿度（RH）函数的水的几种热力学和动力学性质，从初始吸附步骤到完全孔隙填充。在低RH下，SBU的μ3 - OH基团与进入孔隙的初始水分子形成氢键，这在其他孔隙中的μ3 - OH基团与水分子形成氢键之前触发了这些孔隙的填充。我们的分析表明，随着RH增加，MOF - 808的孔隙依次被水填充。据报道，UiO - 66中的水吸附也有类似机制。尽管存在这种相似性，但我们的研究突出了不同的热力学性质和框架特征，它们在MOF - 808和UiO - 66中对吸附过程的影响不同。
