Description:
The potential for nanoporous materials, such as metal organic frameworks (MOFs), to be used effectively for energy storage and gas capture has been hindered by their relatively weak adsorption of gases. The primary approach for weak adsorption has been to develop metal centers that are more active. Such an approach often leads to complex synthesis procedures and release mechanics that are molecule-specific, limiting applicability to targeted molecules. The proposed solution utilizes these nanoporous structures, which are well-suited to adsorb small molecules, and simplifies synthesis in order to retain a wide range of applications.
This innovation takes a novel approach to ameliorating the common gas storage issues faced with using MOFs; the surface of the MOFs are modified in such a way that creates a barrier, preventing the guest molecules from leaving. Surface adsorption of ethylenediamine (EDA) traps the gas inside the MOFs without hindering the total capacity for gas adsorption. Water can be used to pass through the EDA layer to completely remove pre-adsorbed gas molecules. Such a selective EDA membrane opens up new avenues for gas storage and separation, as well as new applications for molecular membranes.
Technical Summary:
Complete sealing of weakly interacting gases inside nanoporous metal organic frameworks (MOFs) was demonstrated with the use of EDA in the loading process as a ‘capping’ compound. Data shows that gas can be trapped by introduction of EDA vapor without hindering the total MOF capacity for gas adsorption. EDA was chosen as a cap due to their terminal amine groups, which are known to interact more strongly with MOFs. It has been shown that EDA molecules cannot easily penetrate into MOFs due to their size and strong interaction with the framework. Thus, the EDA monolayer effectively serves as a selective barrier, preventing gas molecules from moving through the channel openings of the MOFs. Furthermore, water molecules were shown to diffuse through the EDA monolayer without hindrance and fully release molecules sealed within the MOFs at room temperature and low pressure (8 Torr vapor-phase H2O).
Figure 1: Time evolution of the v(CO) band at 2,170 cm-1 upon evacuation at low pressure. (a) Infrared spectra of adsorbed CO and EDA in pristine (bottom) and EDA post-loaded (top) Ni-MOF-74 sample upon evacuation. The intensity of the peaks at 2,170cm-1 represents how much v(CO) is retained. (b) Normalized integrated area of v(CO) band at 2,170cm-1 upon evacuation for pristine (red circles) and EDA post-loaded (black diamonds) Ni-MOF-74 sample.
Figure 2: Time evolution of the vibrational bands vas(CO2) vas(SO2) and δ(CH2) upon evacuation. Infrared spectroscopy was used to measure the amount of gas present, revealing that the EDA post-loaded samples retained the initial concentrations of stored gas.
Value Proposition:
Provides a simple method for efficient adsorption and storage of weakly interacting gases, such as methane and natural gas, in MOFs through use of a molecular cap – an EDA monolayer. These guest molecules are able to be completely released by the addition of water.
Applications:
- Gas storage & separation – methane, carbon dioxide, and natural gas
- Molecular membranes – drug delivery and catalysis
- Carbon capture – greenhouse gas scrubbing and storage
Key Benefits:
- Effective – Gases are completely trapped in the MOF by the EDA monolayer.
- Controlled –Water is applied to fully displace and release the guest molecules.
- Simple – Easy to produce; avoids complex synthesis procedures and release mechanisms.
- Non-Specific – Allows for efficient, controlled storage and release of several small molecules, such as methane and natural gas.
Inventors:
Yves Chabal, Ph.D. - Profile
Kui Tan, Ph. D.
Publication: Nature Communications - Link
Related Link: Laboratory for Surface and Nanostructure Modification
IP Status: Patent pending.
Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.
ID Number: MP-16053
Contact: otc@utdallas.edu