Rapid Guest Exchange and Ultra‐Low Surface Tension Solvents Optimize Metal–Organic Framework Activation

Abstract

Exploratory research into the critical steps in metal-organic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs. It is also demonstrated that choice of a very low surface tension solvent is critical in successfully activating challenging MOFs. MOFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents, such as n-hexane and perfluoropentane, are applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.

The Origin of the Reproduction of Different Nitrogen Uptakes in Covalent Organic Frameworks (COFs)

“…In general, the application region of COFs depends on their textural peculiarity, such as functional units, pore size and surface area . In addition, some anthropogenic factors, including reagent concentrations, reaction conditions, purification procedure, degassing process, and so on, also influence the gas sorption capacity and corresponding functions of COFs . Therefore, it is reasonable that different gas isotherms were reproduced by different experimental groups for the same material at the same conditions …”

“…In the previous studies, the different activation processes are considered to lead to the irreproducibility of gas adsorption on MOFs . The experimentally‐obtained gas adsorption isotherms are usually underestimated with respect to idealized materials.…”

“…If the solvent molecules are not removed carefully and completely, the gas adsorption isotherm for materials could be seriously decreased. Several cases show that different “activation” processes could result in different gas adsorption isotherms for the same material at the same conditions . For example, the N 2 adsorption isotherm for UMCM‐9 activated after n‐hexane treatment is 6 times higher than that after CHCl 2 treatment.…”

“…For example, the N 2 adsorption isotherm for UMCM‐9 activated after n‐hexane treatment is 6 times higher than that after CHCl 2 treatment. This was attributed to UMCM‐9 undergoing partial collapse for the latter case . Besides, there was a 2.2‐fold enhancement in the CO 2 adsorption isotherm of CTF‐1 and 2.4‐fold enhancement in H 2 after a chemical activation process in the presence of KOH at 700 °C …”

Lock‐and‐Key and Shape‐Memory Effects in an Unconventional Synthetic Path to Magnesium Metal–Organic Frameworks

“…We were unable to use heat and vacuum to return CPM-107op back to CPM-107cl ( Figure S12). [17] Further CO 2 adsorption experiments at 195 Kc ould also reproduce the gate-opening isotherm and flexible-to-rigid transformation ( Figure S14). This is probably due to the stronger interaction of CH 2 Cl 2 with the framework (compared to gas molecules).…”