Gas sorption and kinetics of CO2 sorption and transport in a polymorphic microporous MOF with open Zn (II) coordination sites

Sorption equilibrium and kinetics of CO2, N-2 and CH4 on a newly reported Zn-based metal organic framework (Zn-4(pydc)(4)(DMF)(2).3DMF (1)) were studied to evaluate its efficacy for CO2 capture under realistic post-combustion conditions. Adsorption and desorption equilibria were measured gravimetrically for temperatures between 308 K and 338 K and pressures up to 5 bar. The Langmuir adsorption model was used to fit sorption data and the Ideal Adsorbed Solution Theory (IAST) was used to calculate selectivity from single-component isotherms suggesting that separation can be enhanced by a decrease in temperature. The MOF exhibited preferential CO2 adsorption based on the high enthalpy of adsorption and adsorption selectivities of CO2 over N-2 and CH4. Kinetics of adsorption and desorption of CO2 (308K-338 K, pressures up to 1 bar) were fitted to the linear-driving force (LDF) kinetic model, showing a relatively fast adsorption and a low activation energy for adsorption and desorption. Diffusion inside the pores was found to be the rate-limiting step based on fits to the LDF model and the micropore diffusion model. Desorption kinetics studies at 1 bar indicated that CO2 has greater average residence times at all temperatures and lower values of activation energy for desorption than N-2 and CH4. This suggests the selective adsorption and capture of CO2 on (1) will be favored. (C) 2017 Elsevier Ltd. All rights reserved.