Functionalization of metal organic frameworks for enhanced stability under humid environment for CO₂ capture applications

Abstract

Global climate change has been subjected to widespread research interest in recent decades while being attributed for its reason to CO2 anthropogenic accumulation in the atmosphere. Metal-organic frameworks (MOFs) are an emerging new class of nanoporous crystalline solids built of metal coordination sites linked by organic molecules, which have attracted increasing attention since their well-defined porosity, high surface area and tunable functionalities. Among them, Mg/DOBDC, also named as Mg-MOF-74 or CPO-27-Mg, is considered as a strong candidate for CO2 capture in flue gas even in the ambient air, but its hydrophilic properties limit its application since its CO2 uptake capacity dramatically decreases in humid conditions. In this work, we try to impregnate ethylenediamine into the pores of Mg/DOBDC to yield a new porous material ED-Mg/DOBDC that exhibits stability after exposure to water vapor. To investigate structural changes and CO2 uptake capacity in moist conditions, accelerated steam treatment of all samples were performed. Pore characteristics and CO2 uptake capacity of Mg/DOBDC and ED-Mg/DOBDC before and after steaming were measured. ED-Mg/DOBDC showed higher CO2 uptake capacity for both the non-steamed and steamed samples. Also, different ED loadings were suggested by our group`s previous work, and we further investigated the effect of pore characteristics of different ED loadings in the pores of ED-Mg/DOBDC to find the impact of ED molecules in ED-Mg/DOBDC for CO2 capture applications.