Hierarchically Porous Co-MOF-74 Hollow Nanorods for Enhanced Dynamic CO₂ Separation

Abstract

Metal−organic frameworks (MOFs) with coordinatively unsaturated (open) metal sites have been intensively investigated in gas separations because their active sites can selectively interact with targeted molecules such as CO 2 . Although such MOFs have shown to exhibit exceptional CO 2 uptake capacity at equilibrium, the dynamic separation behavior is often not satisfactory to be considered in practical applications. Herein, we report a facile and efficient self-sacrifice template strategy based on the nanoscale Kirkendall effect to form novel Co-MOF-74 hollow nanorods enabling adsorption/desorption of gas molecules in a facilitated manner. The time-dependent microscopic and diffraction examinations were performed to elucidate the formation mechanism of Co-MOF-74 hollow nanorods and to obtain insights into the factors critical to maintaining the rodlike morphology. Such nanostructured MOF exhibited much sharper CO 2 molecular separation behavior than conventional MOF bulk crystals under a dynamic flow condition, because of its enhanced adsorption kinetics through the shortened diffusion distance. Such enhanced dynamic molecular separation behavior was further confirmed by chromatographic separations where a significant peak narrowing was demonstrated.

Metal−Organic Frameworks for High‐Energy Lithium Batteries with Enhanced Safety: Recent Progress and Future Perspectives

“…The faster outward diffusion of Co 2+ than the inward diffusion of linker ions (also known as Kirkendall effect) facilitates the crystal growth of the shell and dissolution of the core, which leads to a hollow structure. Using the same strategy, our group also successfully prepared hierarchically porous Co‐MOF‐74 hollow nanorods for dynamic CO 2 separation . Like porous 2D holey MOF nanosheets, the porous granular shells of hollow MOFs can enhance the diffusion kinetics more than those of their solid counterparts.…”

CO2/N2 Separation Properties of Polyimide-Based Mixed-Matrix Membranes Comprising UiO-66 with Various Functionalities

“…The incorporation of porous fillers into polymer films to form mixed-matrix membranes (MMMs) has been explored with the aim of combining the advantages of polymer and porous fillers. In terms of the choice of porous materials, MOFs have attracted substantial research interest due to properties such as their large accessible surface area and micropore volume [ 17 , 18 , 19 , 20 , 21 ]. MOFs are also capable of pre- or post-synthetic functionalization to promote favorable interaction with target gases such as CO 2 , which is highly polarizable [ 22 , 23 , 24 ].…”

Graphene‐Based Advanced Membrane Applications in Organic Solvent Nanofiltration

“…[ 10,11 ] Thus, more efficient separation techniques are required to meet the energy and economic demand worldwide, considering that a substantial portion of the current energy resources is generated from nonrenewable means, such as coal and fossil fuels. [ 12–16 ]…”