Effect of Varying Amine Functionalities on CO2 Capture of Carboxylated Graphene Oxide-Based Cryogels

Abstract

Graphene cryogels synthesis is reported by amine modification of carboxylated graphene oxide via aqueous carbodiimide chemistry. The effect of the amine type on the formation of the cryogels and their properties is presented. In this respect, ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), were selected. The obtained cryogels were characterized by Fourier Transformed Infrared spectroscopy, thermogravimetric analysis, X-ray spectroscopy, and Scanning electron microscopy. The CO2 adsorption performance was evaluated as a function of amine modification. The results showed the best CO2 adsorption performance was exhibited by ethylenediamine modified aerogel, reaching 2 mmol g−1 at 1 bar and 298 K. While the total N content of the cryogels increased with increasing amine groups, the nitrogen configuration and contributions were determined to have more important influence on the adsorption properties. It is also revealed that the residual oxygen functionalities in the obtained cryogels represent another paramount factor to take into account for improving the CO2 capture properties of amine-modified graphene oxide (GO)-based cryogels.

Hydrothermal-Freeze-Casting of Poly(amidoamine)-Modified Graphene Aerogels towards CO2 Adsorption

“…The selectivity for CO 2 over N 2 increased in the same trend, from 11 to 21 and 38 for the modified aerogels with 0.2 mg mL −1 G7, 0.2 mg mL −1 G3, and 0.1 mg mL −1 G7, respectively. These results indicate the adsorption performance was not only affected by pore characteristics, but also by N content in terms of N/C ratio and nitrogen binding contributions to total nitrogen content, as indicated in recent literature [7,8,10,52].…”

“…The three-dimensional (3D) porous aerogels obtained from reduced graphene oxide (rGO) are considered promising sorbents for CO 2 capture given their low density, interconnected porous network, large surface area, and active sites, which in turn are dependent on the synthesis route [5,6]. A two-step method based on simultaneous solvothermal reduction and self-assembly of GO and a subsequent freeze-drying procedure has been shown as a convenient approach for fabricating 3D GO-based aerogels [5,[7][8][9][10][11][12][13]. Varying solvothermal conditions have been studied for the gelation and self-assembly of GO, such as temperature, duration, GO concentration, or GO flake size.…”

“…Small or large molecules containing amine groups have been reported for chemical modification of epoxide and carboxylic groups in GO to tailor its surface chemistry towards improved adsorption properties [10]. In this respect, poly(amidoamine) (PAMAM) dendrimers have attracted interest as they are non-volatile molecules with a high density of functional amine end groups and large surface area, thus providing an increased number of active sites, which are requisites for producing structures with improved performance [20].…”

Understanding the Adsorption Capacity for CO2 in Reduced Graphene Oxide (rGO) and Modified Ones with Different Heteroatoms in Relation to Surface and Textural Characteristics

“…The majority of the modification reactions are based on the introduction of the N in the structure. Some of these examples are based on ethylenediamine, diethylenetriamine, triethylenetetramine (showing CO 2 adsorption of 2.0 mmol/g at 1 bar and 298 K [18], with urea (CO 2 adsorption at atmospheric pressure, and 25 • C of 2.40 mmol/g) [19], with hydrazine during reduction (for supercapacitors) [20] and ethylenediamine (1.1 mmol/g of CO 2 adsorption) [21]. Some other works involve doping with S, P, and N grown with Co 9 S 8 nanoparticles (as a bifunctional catalyst) [22] or silylation by employing three distinct silica precursors (CO 2 adsorption of 3.5 mmol/g at 5 bar and 0 • C [23] or thiolene click reaction [24].…”

“…Finally, other works can be found by using MgO, rGO, and amorphous carbon to prepare sandwich-like structures (CO 2 adsorption up to 31.5 wt % at 27 • C, 1 bar CO 2 22.5 wt % under the simulated flue gas) [25]. In most of these works it was concluded that the functionalization of 3D rGO materials by introducing various heteroatoms functional groups is a useful tool to improve the textural properties (porosity and SA) [18,19,23,25], CO 2 capture capacity [18,19,21,23,25] and/or selectivity over N 2 [19,21].…”