Role of Temperature in the Structure of Zn(II)-1,4,-BDC Metal-Organic Frameworks and their Adsorption and Diffusion Properties for Carbon Dioxide

Abstract

The role of reaction temperature in the structure of Zn(II)-1,4,-Benzendicarboxylic-MOFs (Zn-BDC-MOFs) and subsequently their CO2 adsorption properties were investigated. Crystal morphology and phase structure of the Zn-BDC-MOFs were characterized by SEM and PXRD. Stability and textual properties of the Zn-BDC-MOFs were analyzed by using accelerated surface area and porosimetry apparatus (ASAP) and thermogravimetric analysis (TG). Adsorption equilibrium and diffusion of CO2 on these materials were experimentally studied by the gravimetric method in the pressure range up to 1 atm at room temperature. Results showed that reaction temperature changed the coordination mode of 1,4,-Benzendicarboxylic acid ligand and caused the different structures and pore texture of Zn-BDC-MOFs. High reaction temperature was good for the generation of the three-dimensional MOFs with a higher adsorption capacity for CO2 but lower gas diffusivity. In contrast, low reaction temperature could cause the monodentate ligand in metal centers and form the low-dimensional MOFs with a lower adsorption capacity for CO2 but higher gas diffusivity. The order of CO2 adsorption uptake and diffusion time constant were given as MOF-130T > MOF-50T > MOF-100T > MOF-75T and MOF-50T > MOF-75T > MOF-100T > MOF-130T, respectively.