Atomic-Level Insights into CO2 Adsorption in a Defective Amino-Functionalized MOF through In Situ HR-PXRD

Rising anthropogenic CO2 levels necessitate the development of efficient carbon capture and storage (CCS) technologies, with metal-organic frameworks (MOFs) emerging as promising adsorbent platforms. The CO2 adsorption behavior of these materials is significantly influenced by their tunable microstructural features, including surface area, network topology, and the presence of defective sites[1]. While traditional gas sorption techniques offer valuable macroscopic insights, a comprehensive understanding of the underlying structural and thermodynamic mechanisms is crucial for optimizing adsorbent performance. Our group recently described the application of a powerful in situ high-resolution powder X-ray diffraction (HR-PXRD) protocol[2], performed under controlled CO2 atmospheres with systematic pressure variations, to directly derive structural adsorption isotherms for the highly stable, pyrazolate based MOF Fe2(BDP)3 [H2BDP = 1,4-bis(1H-pyrazol-4-yl)benzene][3], This approach, coupled with Rietveld refinement and simulated annealing, enabled the precise localization of physisorbed CO2 molecules and determination of isosteric heats of adsorption, effectively bridging the gap between structural and thermodynamic information[4]. To further validate and expand the scope of this HR-PXRD protocol, the present study focuses on its application to amino-tagged derivatives of Fe2(BDP)3, namely Fe2(BDP)3-x(BDP-NH2)x (x = 1.5, 3), explicitly considering the intrinsically defective nature of this family of architectures. By investigating these functionalized materials, we aim to elucidate how the introduction of polar amino groups, known to enhance CO2 uptake via quadrupole interactions, influences the structural and thermodynamic aspects of CO2 adsorption within the framework, providing an extensive overview of structure-property relationships for advanced CCS applications. References [1] E. López-Maya, C. Montoro, et al. Adv. Funct. Mater. 2014, 24, 6130-6135. [2] R. Vismara, S. Terruzzi, et al. Adv. Mater. 2024, 36, 2209907. [3] Z. R. Herm, B. M. Wiers, et al. Science 2006, 340, 960-964. [4] A. Nuhnen and C. Janiak. Dalton Trans. 2020, 49, 10295-10307. Rising anthropogenic CO2 levels necessitate the development of efficient carbon capture and storage (CCS) technologies, with metal-organic frameworks (MOFs) emerging as promising adsorbent platforms. The CO2 adsorption behavior of these materials is significantly influenced by their tunable microstructural features, including surface area, network topology, and the presence of defective sites[1]. While traditional gas sorption techniques offer valuable macroscopic insights, a comprehensive understanding of the underlying structural and thermodynamic mechanisms is crucial for optimizing adsorbent performance. Our group recently described the application of a powerful in situ high-resolution powder X-ray diffraction (HR-PXRD) protocol[2], performed under controlled CO2 atmospheres with systematic pressure variations, to directly derive structural adsorption isotherms for the highly stable, pyrazolate based MOF Fe2(BDP)3 [H2BDP = 1,4-bis(1H-pyrazol-4-yl)benzene][3], This approach, coupled with Rietveld refinement and simulated annealing, enabled the precise localization of physisorbed CO2 molecules and determination of isosteric heats of adsorption, effectively bridging the gap between structural and thermodynamic information[4]. To further validate and expand the scope of this HR-PXRD protocol, the present study focuses on its application to amino-tagged derivatives of Fe2(BDP)3, namely Fe2(BDP)3-x(BDP-NH2)x (x = 1.5, 3), explicitly considering the intrinsically defective nature of this family of architectures. By investigating these functionalized materials, we aim to elucidate how the introduction of polar amino groups, known to enhance CO2 uptake via quadrupole interactions, influences the structural and thermodynamic aspects of CO2 adsorption within the framework, providing an extensive overview of structure-property relationships for advanced CCS applications. References [1] E. López-Maya, C. Montoro, et al. Adv. Funct. Mater. 2014, 24, 6130-6135. [2] R. Vismara, S. Terruzzi, et al. Adv. Mater. 2024, 36, 2209907. [3] Z. R. Herm, B. M. Wiers, et al. Science 2006, 340, 960-964. [4] A. Nuhnen and C. Janiak. Dalton Trans. 2020, 49, 10295-10307.