Porous carbon nanosheets with precisely tunable thickness and selective CO2 adsorption properties

Abstract

We report the wet-chemistry synthesis of a new type of porous carbon nanosheet whose thickness can be precisely controlled over the nanometer length scale. This feature is distinct from conventional porous carbons that are composed of micron-sized or larger skeletons, and whose structure is less controlled.The synthesis uses graphene oxide (GO) as the shape-directing agent and asparagine as the bridging molecule that connects the GO and in situ grown polymers by electrostatic interaction between the molecules. The assembly of the nanosheets can produce macroscopic structures, i.e., hierarchically porous carbon monoliths which have a mechanical strength of up to 28.9 MPa, the highest reported for the analogues. The synthesis provides precise control of porous carbons over both microscopic and macroscopic structures at the same time. In all syntheses the graphene content used was in the range 0.5-2.6 wt%, which is significantly lower than that of common surfactants used in the synthesis of porous materials. This indicates the strong shape-directing function of GO. In addition, the overall thickness of the nanosheets can be tuned from 20 to 200 nm according to a fitted linear correlation between the carbon precursor/GO mass ratio and the coating thickness. The porous carbon nanosheets show impressive CO 2 adsorption capacity under equilibrium, good separation ability of CO 2 from N 2 under dynamic conditions, and easy regeneration. The highest CO 2 adsorption capacities can reach 5.67 and 3.54 CO 2 molecules per nm 3 pore volume and per nm 2 surface area at 25 C and $1 bar. Broader contextThe control of anthropogenic CO 2 emissions is a crucial matter in view of the signicant role that this gas plays in global climate change. In recent years, great efforts have been directed towards the CO 2 capture and storage. Compared with the liquid-phase absorption process, the use of porous solids, especially porous carbons, as sorbents for capturing CO 2 has shown great promise due to the low cost, high availability, large surface area, an easy-to-design pore structure, hydrophobicity and low energy requirements for regeneration. Here we present a novel route for the preparation of porous carbon nanosheets (PCNs) whose thickness can be precisely controlled over the nanometer length scale from 20 to 200 nm. Benetting from the short diffusion paths and high microporosity, the PCNs exhibit high sorption capacity, fast sorption kinetics and a good CO 2 -N 2 selectivity.

Direct Carbonization of Cyanopyridinium Crystalline Dicationic Salts into Nitrogen-Enriched Ultra-Microporous Carbons toward Excellent CO2 Adsorption

“…The values are much higher than most of the reported porous carbons for CO 2 capture under identical conditions, 15,18,31,59−61 which is of great significance to broaden its potential application in separating CO 2 from dilute gases. 61 In addition, five-cycling reproducible CO 2 sorption isotherms are observed ( Figure S19), suggesting their good regeneration stability for CO 2 capture.…”

Highly Porous Nitrogen-Doped Carbon Nanofibers as Efficient Metal-Free Catalysts toward the Electrocatalytic Oxygen Reduction Reaction

“…And there is no peak found in the region of mesopore or macropore, showing that ANCNFs are really microporous resulting from the etching effect of KOH. 26 Furthermore, the formation of another micropore system (1.1 nm)…”

Interpenetration in coordination polymers: structural diversities toward porous functional materials

“…The earliest known porous materials are inorganic zeolites, porous carbon and silica. Zeolites are widely used materials in industry for catalysis and water purification while porous carbon and silica materials are also promising for high capacity gas storage and other related properties [6][7][8]. All these materials do contain enough void space but lack modifiable pore surface and tunable surface area.…”