[ n ]‐Oligourea‐Based Green Sorbents with Enhanced CO 2 Sorption Capacity

A new series of [ n ]‐oligoureas ( [ n ]‐OU s, n = 4 , 7 , 10 , and 12 ) green solid sorbents was prepared following a base‐catalyzed, microwave‐assisted oligomerization reaction. The materials were characterized by NMR and IR spectroscopy, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and XRD. Decomposition temperatures at 50 % weight loss ( T d50 ) were ca. 350 °C for all oligomers. Urea and urethane functional groups indicated by IR spectroscopy confirmed the formation of the sorbent. The CO 2 capturing capacities were determined at 35 °C and 1.0 bar (gravimetric method). Accordingly, [10]‐OU had the highest CO 2 sorption capacity among the others (18.90 and 22.70 mg   CO   2 g sorbent −1 ) at two different activation temperatures (60 or 100 °C, respectively). Chemisorption was the principal mechanism for CO 2 capture. Cyclic CO 2 sorption/desorption measurements were carried out to test the recyclability of [10]‐OU . Activating the sample at 60 °C, three stable CO 2 sorption cycles were achieved after running the first cycle.