Metal-organic frameworks (MOFs) have attracted great attention as potential hydrogen storage and carbon capture materials due to their high surface areas and tunable pore properties. However, their practical applications are still limited since several problems are unsolved such as low gas uptake capacities at ambient temperature, low stability against water, and low adsorption selectivity from the mixture gas (in case of carbon capture). To achieve high hydrogen storage and high carbon capture capability from the flue gas, we have synthesized and modified the pore space of MOFs by various strategies.To enhance H2 storage capacities of MOFs at ambient temperature, the interaction energies between the frameworks and hydrogen gas should be increased. Creation of open metal sites, functionalization of the ligand,and inclusion of crown ethers in the pores were seen to increase the interaction energy in the MOFs, but the effects were not so great. Impregnating Pd and Mg nanoparticles, which strongly bind H2 molecules, in the pores of the MOFs, significantly increases hydrogen storage. Also, the MOFs incorporating crown ether moieties that bind K+ and NH4+ ion show enhanced hydrogen storage.For carbon dioxide capture, an ideal MOF should have a high gas uptake capacity, a high CO2 adsorption selectivity from a gas mixture, fast adsorption and desorption kinetics, high stability against water, and low energy penalty for regeneration of the adsorbents. We have achieved high CO2 adsorption selectivity by tailoring the flexibility of the MOFs such that the gates of the MOFs could open and close only for CO2 molecules while not adsorbing other gases.We found that charged MOFs are much better than neutral MOFs for selective carbon capture. When the pores are modified by impregnating metal ions or a polyamine, the materials show significantly enhanced carbon capture abilities.

Pore engineering of metal-organic frameworks for hydrogen storage and carbon capture

248th National Meeting (2014)

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