Diethylene glycolamine-assisted rapid synthesis of mechanically robust pyrogallol-based carbon monoliths for CO2 capture and separation

Abstract

Carbon monoliths have the advantages of good heat resistance and no need for molding during use. However, in practical applications, due to its low strength, it often suffers from wear and breakage during multiple adsorption-desorption cycles, which is not conducive to CO2 adsorption. Pyrogallol and formaldehyde-based polymers were used as carbon precursors, triblock copolymer Pluronic F127 was used as a structural directing agent, and diethylene glycolamine (DGA) as both the polymerization crosslinking agent and structural assembly promoter. In the presence of DGA, the solution can quickly gel within 15–20 min at 90 °C. No catalyst required, no environmental pollution, low cost, and mild reaction. Hydrogen bond interaction and poly(benzoxazine-co-resol) self-assembly synthesized homogeneous and crack-free polymer monoliths. A sturdy framework of carbon monoliths was obtained by adjusting the content of DGA and carbonization temperature. The kind of carbon monolith not only has a fully interconnected mesoporous structure and maintains good shape even after being magnified three times. The tight network skeleton enables it to have good mechanical strength and withstand a pressure of 8.1 MPa, which is 41 times greater than that of nano-casting and soft template carbon monoliths (0.19 and 0.2 MPa). The presence of nitrogen-containing groups and pore structures gives it good CO2 capture ability (0.9–2.8 mmol/g, 1 bar, 298 K), superior to the regular mesoporous carbon prepared by soft and hard template methods (1.5 and 1.7 mmol/g). Meanwhile, it exhibits high selectivity for capturing CO2 over N2 from a 15% (v%) CO2/N2 mixture. They undergo a facile CO2 release in an argon stream at 25 °C, indicating a good regeneration capacity. After five testing cycles, the carbon monolith still maintained good adsorption and separation performance, with adsorption capacity maintained at 98–100% of the initial adsorption capacity.

Keywords

• Carbon monolith
• CO2 capture
• Mechanical strength
• Rapid synthesis