Metal-organic framework (MOF-808) functionalized with ethyleneamines: Selective adsorbent to capture CO₂under low pressure

A Zr-based metal-organic framework (MOF), MOF-808, was functionalized with ethyleneamines such as tetraethylenepentamine (TEPA), diethylenetriamine (DETA), and ethylenediamine (ED) to utilize the obtained MOFs in selective capture of CO2 from offgas under low pressure. The modification was done firstly in the liquid phase via an acid-base reaction (using μ-OH of the MOF), and TEPA was the most effective among the tested ethyleneamines because of the low basicity of the TEPA. MOF-808s functionalized with TEPA were very efficient in CO2 capture because of loaded primary and secondary amino groups. For example, one MOF-808, functionalized with an adequate quantity of TEPA, showed remarkable performances in CO2 adsorption with a very high ideal adsorption solution theory selectivity of 256 which is around 7 times that of the pristine MOF-808. Moreover, the modified MOF-808 adsorbed around 2.5 times CO2 that of the pristine M-808 at 15 kPa. The noticeable performance of the functionalized MOF-808 was explained with the loaded amino groups that are capable of a Lewis acid-base interaction with CO2 to form carbamates. This work will pave the way to modify a MOF, although without open metal sites, to introduce amino groups that will be very effective in selective capturing of CO2 from offgas.