The Effect of Water Co-adsorption on the Adsorption of Formaldehyde in Fe-HHTP-MOF Metal-Organic Materials.

Because of the existence of moisture in indoor air, it is still a serious challenge to capture formaldehyde indoors with the metal-organic material Fe-HHTP-MOF. To explore the relationship between the structure and performance of Fe-HHTP-MOF in dry and humid air, molecular dynamics simulation was used to study the adsorption amount of Fe-HHTP-MOF for formaldehyde and water under different temperatures and adsorption pressures, as well as the adsorption amount of Fe-HHTP-MOF for formaldehyde in the presence of both water and formaldehyde, and the differences in adsorption of formaldehyde and water by Fe-HHTP-MOF were compared and analyzed when water coexisted. The results show that under single-component isothermal adsorption, the hydrogen bond energy formed by Fe-HHTP-MOF adsorbing H2O molecules is much greater than the van der Waals energy formed by adsorbing HCHO molecules. In a dry state, as the temperature increases, the adsorption amount of HCHO molecules decreases. When the temperature rises to 313.15 K, even if the temperature is further increased, the effect on the adsorption amount of HCHO molecules is small. Moreover, after the adsorption pressure is greater than 7.78 MPa, the adsorption amount of HCHO molecules tends to flatten. When H2O molecules coexist, at the same adsorption pressure and temperature, H2O molecules with polar functional groups preferentially occupy the adsorption sites, and the adsorption amount of HCHO molecules in the presence of H2O is lower than that in the dry state. As the temperature increases, under the same adsorption pressure, the intermolecular interaction strengthens, and the molecular activity increases. The influence of water molecules on the adsorption of HCHO by Fe-HHTP-MOF weakens, and HCHO molecules reach the saturated adsorption site ahead of time. The adsorption energy of H2O is greater than that of HCHO, indicating that the presence of water may hinder the capture of HCHO.