Graphitic Carbon Nitride Functionalized with Polyethylenimine for Highly Effective Capture of Carbon Dioxide

Graphitic carbon nitride (g-C 3 N 4 ) is a kind of two-dimensional material with unique properties, and can be facilely prepared from low-cost precursors. It has promising application in CO 2 capture. However, the low alkalinity of nitrogen species in g-C 3 N 4 makes its interaction with CO 2 very weak. Aiming to promote the use of g-C 3 N 4 for CO 2 capture, a class of amine-functionalized g-C 3 N 4 adsorbents were designed in the present work. The amine-functionalized g-C 3 N 4 adsorbents were prepared by physical impregnation of polyethylenimine (PEI), which contains many amine groups and exhibits extremely low volatility, into the stacked pores of g-C 3 N 4 . It is found that, after the amine functionalization, the performance of g-C 3 N 4 for CO 2 capture (including capacities and selectivities) are significantly improved. The highest CO 2 capacity of PEI–g-C 3 N 4 composites is 3.77 mmol/g when determined at 100 °C and ambient pressure, being superior to most of those of other g-C 3 N 4 materials and solid amines reported in the literature. Furthermore, the CO 2 adsorbed by PEI–g-C 3 N 4 composites can be facilely stripped out by concentration swing, and the loss in CO 2 capacity is negligible after 10 cycles of adsorption and desorption.