Periodic Reporting for period 4 - COSMOS (Computational Simulations of MOFs for Gas Separations)
Reporting period: 2022-04-01 to 2024-03-31
Metal organic frameworks (MOFs) are crystalline materials composed of metal complexes that are linked by organic ligands to create highly porous frameworks. They appeared as fascinatingly promising materials to be used as adsorbents and membranes for gas separations due to the large variety in their pore sizes, shapes, and chemistries. Over 100,000 MOFs with different chemical compositions have been reported to date and the number is very rapidly increasing. Existence of large number of MOFs creates excellent opportunities to develop energy-efficient gas separation technologies. At the same time, this large materials space imposes a challenge for the material search. This project aims to accelerate material search for CO2 capture and H2 recovery by developing comprehensive computational approaches and applying them to thousands of MOFs to identify the best adsorbents and membranes. With this aim, we performed high-throughput molecular simulations to assess adsorption and diffusion properties of gas mixtures in MOFs and then used this molecular-level information to predict adsorbent and membrane properties of MOFs for various different gas separations. We specifically focused on CO2/CH4, CO2/N2, CO2/H2, CH4/H2 and N2/H2 separations given their environmental, industrial, social and economic importance. CO2/CH4 separation is known as natural gas purification, it has great energetic and economical importance because CO2 reduces the energy content of the natural gas. CO2/N2 separation is known as flue gas separation, it has an environmental and social importance because ~40% of the total CO2 released to the atmosphere comes from flue gas emission. Identification of materials that can achieve CO2/N2 separation with high performance will play a great role in reducing the global warming and related environmental and health problems. Separation of H2 from CO2, CH4 and N2 is important since H2 is used as a clean energy carrier for stationary power and transportation markets. The overall objectives of this project are as follows: (a) to build a complete and accurate MOF library using computational approaches, (b) to perform molecular simulations to compute adsorption and diffusion of gas mixtures in MOFs, (c) to evaluate gas separation performance of MOF adsorbents and membranes, (d) to identify the best adsorbent and membrane materials by ranking MOFs based on diverse metrics, (e) to reveal structure-performance relations for the best performing MOFs, (f) to computationally design of new MOFs with exceptional gas separation performance and experimentally test these new materials under practical operating conditions.
The ultimate objective of this project is assessing adsorption and diffusion properties of gas mixtures in metal organic frameworks (MOFs) using molecular simulations and then using this data to predict adsorbent and membrane properties of MOFs for CO2/CH4, CO2/N2, CO2/H2, CH4/H2 and N2/H2 separations. We used a novel approach of research with original methodology and worked on eight different work packages to achieve these objectives. Briefly, we provided an extensive comparative analysis of MOF databases, validated the accuracy of our computational approach by comparing our simulated results with the available experimental gas adsorption data of MOFs. We designed and developed a multi-level, high-throughput computational screening methodology based on molecular simulations to examine the entire MOF database both for adsorption-based and membrane-based separation of various gas mixtures. We then used this simulation data to compute adsorbent and membrane performance evaluation metrics of MOFs and ranked several thousands of MOFs based on these metrics. The most promising MOF adsorbents and membranes were identified. MOFs were compared with zeolites and activated carbons in adsorption-based gas separations whereas they were compared with polymers for membrane-based gas separations. Results showed that there are hundreds of MOFs that can easily replace the traditional porous adsorbent and membrane materials due to their higher gas selectivities. Structure-performance relations were established to show which structural characteristics of MOFs lead to high performance materials. MOFs were experimentally studied as adsorbents in the lab scale. Results of these works were published as 72 manuscripts in international, peer-reviewed, highly prestigious journals at the end of the project where 22 of these publications were produced in the fourth reporting period.
We designed and used a multi-level, state-of-the-art, high-throughput computational screening approach with increasing complexity to screen very large numbers of MOFs for various gas separations. Molecular-level information that we obtained from these simulations about the gas behaviors in MOFs will accelerate the development of MOFs not only for gas separations but also for various chemical applications such as catalysis, sensing. We established an online, freely accessible database https://cosmoserc.ku.edu.tr(opens in new window) for the first time in the literature, which reports all of the simulation results on adsorbent and membrane performance metrics of MOFs for CO2/N2, CO2/CH4, and CO2/N2/CH4 separations in addition to structural properties of MOFs such as pore sizes and porosities. This database will be breakthrough for chemists and material scientist working on a large variety of applications of MOFs. Due to the ongoing increase in the number of synthesized MOFs, we will continue to perform molecular simulations on new materials and update the library until the end of the project. Using the performance evaluation metrics, we identified the best MOFs for each gas separation that we considered in this project. This will guide the scientific studies to more useful materials and provide valuable information that can lead to new and effective gas separation technologies based on MOFs in near future. Due to the ongoing increase in the number of synthesized MOFs, we will continue to perform molecular simulations on new materials and update our ‘best materials’ lists until the end of the project. Structure-performance relations of MOFs that we established for each gas separation is beyond the-state-of-the-art because this will let the experimentalist to select MOFs with pre-determined structural characteristics to achieve desired separations. We in silico designed new MOFs by changing the metal type of an existing MOF and showed significant performance improvements. We also performed experiments on MOFs and identified several MOF composites showing enhanced gas separation potential.