Synthesis of Ca-based metal–organic frameworks from carbide slag for CO2 adsorption

Metal-organic frameworks (MOFs) are a promising material for CO2 adsorption because of their great specific surface area, well-ordered porous structures ordered porous structure and various means available for functionalization. In this work, the calcium squarate (UTSA-280) was synthesized from carbide slag without pretreatment at room temperature by a rapid mechanochemical method, and then was further functionalized with tetraethylenepentamine (TEPA) to prepare CO2 adsorbents. The effects of water content, ball milling frequency, adsorption temperature, and TEPA loading on CO2 adsorption performance of various adsorbents were investigated. The results showed that the CO2 adsorption of the synthesized MOFs increased firstly and then decreased with increasing water content and ball milling frequency. The synthesized MOFs with water content of 300 mmol and ball milling frequency of 15 HZ exhibited the best crystallinity. The addition of TEPA provided additional adsorption sites and led to the increase of CO2 adsorption capacity. The UTSA-280–300-15-40TEPA demonstrated the highest CO2 adsorption capacity (2.89 mmol/g) at 25 °C. The CO2 adsorption kinetics analysis showed that the Avrami model fitted well with the experimental results. Furthermore, the UTSA-280–300-15-40TEPA exhibited excellent chemical stability during the adsorption–desorption cycles, with only a 14.53 % decrease in adsorption capacity after 10 cycles. This work demonstrated the possibility of preparing UTSA-280 using carbide slag for effective CO2 adsorption.