Selective CO2 adsorption over a Zr-based metal–organic framework functionalized with tris(2-aminoethyl)amine

Selective capture of CO2 from off-gas or even the atmosphere is very important against global warming. In this work, a stable Zr-based MOF (MOF-808) was loaded with –COOH group and was further functionalized with tris(2-aminoethyl)amine (TREN), via a reaction between –NH2 of TREN and –COOH sites. The derived materials were analyzed with X-ray diffraction, scanning electron microscopy, FTIR, X-ray photoelectron spectroscopy, thermogravimetry analysis, elemental analysis, and nitrogen adsorption at 77 K; utilized in the adsorption of CO2 and N2 at relatively low pressure up to 100 kPa. One functionalized MOF-808 prepared in this work (named MOF808-EDTA-TREN(0.3)) showed remarkable performances in the selective capture of CO2 under low pressure. For example, the invented MOF exhibited the highest selectivity (based on ideal adsorbed solution theory) in CO2 capture from N2 and CO2 (SCO2/N2: 519 at 100 kPa) compared with any reported results, thus far, using MOF-808-based materials. Moreover, MOF808-EDTA-TREN(0.3) was recyclable up to the fifth run upon vacuum treatment. The noticeable performances of MOF808-EDTA-TREN(0.3) in CO2 adsorption could be explained by the loaded –NH2 sites of TREN (that are effective in carbamates formation) and bulky TREN that decreases the nitrogen adsorption because of the reduced porosity of the MOF. In brief, loading bulky amines with ample amino groups like TREN can be suggested as an attractive way to modify a MOF for selective CO2 capture from off-gas of various industries.