Novel strategies for efficient carbon capture and release by metal-organic frameworks using computational methods – Computationalcarboncapture

We will adopt several complementary methods such as DFT, ab initio molecular dynamics, many-body perturbation theory, grand canonical Monte Carlo and classical molecular dynamics. We will characterize the interaction between CO2 and the specific components of the MOFs, its binding geometry, we will study the isomerization mechanism of the photoactive molecules inside the MOF using excited-state methods, we will study the spin crossover transition and predict the thermodynamics of CO2 adsorption in order to study the mechanism of carbon dioxide uptake at a molecular level and fully characterize the process for future
industrial CO2 capture.

We have studied both families of MOFs. Regarding the spin crossover MOFs, we have predicted the CO2 interaction and configuration for three metal-substitions of a Hofman-type MOF and characterized the magnetic properties using a combination of experiments and
theory. The understanding acquired during this first initial study will be used to carry on the rest of the project.
Regarding photoactive MOFs, we have computed the adsorption isotherm using DFT and grand canonical Monte Carlo for the PCN-123 MOF after and before light treatment. For the first time we could provide a clear and detailed understading of the pioneering experimental work by Park [JACS 123, 99, 2012] where the dramatic change in the adsorption properties of this MOF upon light irradiation was reported for the first time. We explain the experiments by demonstrating that the uptake difference arises from the blocking of adsorption sites from the
cis conformation of the photoactive molecules anchored to the MOF. We also show that particular care must be taken when addressing the isomerization of a molecule inside a MOF.
This work has been performed in collaboration with Ohio State University (LiChiang Lin) two postdocs (Azzam Charaf Eddin and Chi-Ta
Yang) and ILL (Alberto Velamazan).

Regarding the study of photoactive MOFs, we will continue studying the PCN-123 MOF for a few metal substitutions in order to predict the MOF with the highest working capacity. We will also study two other families of MOFs which have not yet been used as frameworks for photosensitive molecule functionalization but that show great promise for an efficient carbon capture (IRMOF-74-II and IRMOF-74-III). We will also develop the project on spin crossover MOFs which is still in its initial stage.

We have started writing a manuscript on the results we have obtained so far on the Hofman-type clathrate. We intend to submit it for publication to the Journal of Physical Chemistry C.
After we finish the calculations of the CO2 uptake by the cis and trans isomers in photoactive PCN-123 MOF we will write the results in a manuscript that we intend to submit to the Journal of American Chemical Society. The novelty of the result justifies its publication is such a high
impact journal.

Carbon dioxide generated from the combustion of fossil fuels for heat and electricity production is a major contributor to climate change. Although great efforts and investments are being made to increase the share of renewable energy in the primary energy supply and to improve the conservation efficiency of fossil fuel resources, addressing climate change concerns during the coming decades requires significant contributions from carbon capture and sequestration. Several technologies and different materials have been studied in the past 10 years as possible solutions to the carbon capture problem. Nevertheless, no final solution has been achieved mainly due to their poor energy efficiency.
Here we propose to address the carbon capture problem using original strategies. We propose to computationally design novel metal-organic framework (MOF) whose affinity for CO2 can be modified under light irradiation or by heating so that the adsorption and desorption can be performed each at the most convenient conditions, allowing to achieve a high energy efficiency and therefore a limited cost. We will adopt several complementary methods such as DFT, ab initio molecular dynamics, many-body perturbation theory, grand canonical Monte Carlo and classical molecular dynamics to study the mechanism of uptake at a molecular level and fully characterize the process for industrial CO2 capture.
The first class of MOFs that will be studied are called photo-active MOFs. These consist of photo-active molecules covalently anchored onto the internal surface of the MOF in such a way that gas capture and release can be achieved by opening and closing of the available pores upon light excitation. In this way, the lower uptake obtained under light treatment will allow for a reduced energy penalty. Only few of these have been synthesized during the past 5 years and their efficiency in capturing CO2 was so poor that no other materials have been recently synthesized or studied computationally. We propose here to modify the existing materials in order to achieve an unprecedented performance. We will use an educated guess in the choice of the MOF substituted components and will show that for these materials achieving a high efficiency is possible. In order to do so we will fully characterize the binding mechanism and the isomerization mechanism under light treatment and report the adsorption isotherm before and after light irradiation.
The second class of MOFs studied in this project are spin-crossover MOFs. These contain transition metal sites that undergo a change in their electronic configuration as a function of temperature. Here, we propose to employ this mechanism, for the first time, in order obtain novel materials whose affinity for CO2 can be dramatically reduced with temperature, reducing, as for photo-active MOFs, the cost of the process.
Although this mechanism has not been explored before in the context of carbon capture, a few SCO MOFs have already been synthesized. Our strategy is to modify these MOFs accordingly such that the process could be used for industrial CO2 capture. This will require the study of the transition temperature, hysteresis, mechanism of binding and the thermodynamics of uptake as a function of temperature and pressure of the gas molecule.
The diffusion properties and the selectivity over N2 will be predicted for all both MOFs families.
Although this is a fully computational work, we have on-going collaborations and are in contact with experimental groups interested in these materials. The understanding developed during this work will motivate their future synthetic effort and open the way to novel research fields based on these materials.