Tailored porous structure and CO2 adsorption capacity of Mg-MOF-74 via solvent polarity regulation

Metal-organic frameworks (MOFs) are promising materials for CO 2 adsorption and capture. The unique crystal structure and the open porous structure of MOFs are key factors affecting their CO 2 adsorption performance, but the precise tuning of MOF structures remains a challenge. Herein, we applied the Kamlet-Taft method to investigate the effect of solvent proton-supplying/accepting capaity (β/α parameters) on the structure and CO 2 adsorption performance of Mg-MOF-74 by tuning the reaction solvent polarity. It was found that the ratio of the nucleation rate/growth rate of Mg-MOF-74 could be effectively controlled by adjusting the β/α value of the solvent, realizing the regulation of the crystal structure and morphology of Mg-MOF-74. In addition, the size of solvent molecules played a crucial role in the pore size of Mg-MOF-74. Interestingly, the solvent molecules were competitively coordinated with ligands and participate in the growth of Mg-MOF-74 upon decreasing the β/α value. The crystal structure, morphology and pore size of Mg-MOF-74 could be precisely regulated by the β/α value and molecular size of the reaction solvent, and the highest performing Mg-MOF-74 exhibited a CO 2 adsorption capacity of 7.38 mmol/g.