In the transition to a clean-energy future, CO2 separations will likely play a critical role in mitigating current greenhouse gas emissions and facilitating conversion to cleaner-burning and renewable fuels. New materials with high working capacities and selectivity for CO2 as well as low regeneration energies are needed to achieve these separations efficiently at scale. Toward that end, we have synthesized and evaluated a new class of diamine-appended metal–organic frameworks of the form (diamine)2Mg2(dobpdc) (dobpdc4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) that feature step-shaped CO2 adsorption isotherms resulting from cooperative and reversible binding of CO2 in ammonium carbamate chains. High-throughput adsorption isotherm data correlated with in situ X-ray single crystal structures demonstrate that small modifications to the diamine structure can shift the threshold pressure for cooperative CO2 adsorption over four orders of magnitude at a given temperature. The observed trends can be leveraged in the rational design of CO2 adsorbents precisely tailored to match the conditions of a given separation process. This unparalleled versatility is coupled with high working capacities and low projected energy costs, supporting the utility of diamine-appended frameworks in a wide array of CO2 separations.

Controlling cooperative CO2 adsorption in diamine-appended Mg2(dobpdc) metal–organic frameworks

253rd National Meeting (2017)

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