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In the current work, we presented the synthesis of N-doped hierarchically porous carbons (NDHPCs) through chemical activation of hierarchically structured precursor derived from polyvinylpyrrolidone (PVP) and magnesium acetate tetrahydrate. Magnesium acetate tetrahydrate served as the blowing agent, and its decomposition product MgO served as the in-situ formed hard template. Combined with KHCO 3 activation, the NDHPCs demonstrated a unique micro- meso -macroporous structure. Owing to the highly porous structure (1560–2545 m2/g) and enriched N-doping (1.48–6.31 wt%), the NDHPCs were investigated as potential CO 2 adsorbents in both post-combustion capture and pre-combustion capture applications. When the adsorption temperature was 25 °C, the samples showed outstanding capture performances at both 1 bar (2.97–3.88 mmol/g) and 20 bar (13.24–19.89 mmol/g). The adsorption performances were further analyzed with grand canonical Monte Carlo (GCMC) simulation. Effects of various physicochemical properties on CO 2 adsorption at different pressures were thus revealed with a combined experimental-theoretical approach. [Display omitted] • NDHPCs with unique micro- meso -macroporous structure are prepared. • The precursor is prepared through chemical blowing and in-situ hard template. • The NDHPCs demonstrate high S BET (1560–2545 m2/g) and N content (1.48–6.31 wt%). • At 25 °C and 20 bar, CO 2 uptake of the NDHPCs reaches 19.89 mmol/g. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microporous nitrogen doped carbon is prepared from camphor leaves. • A very high specific surface area of 1736 m2/g is achieved. • Nitrogen doping exhibits positive effects on CO 2 uptake and adsorption selectivity. Abstract In this work, we reported the synthesis of nitrogen doped carbons from camphor tree leaves. The leaves were carbonized and then activated with KOH, and the nitrogen element in the leaves was used as the nitrogen source. The carbon showed a high surface area of 1736 m2/g. A high CO 2 uptake of 5.86 mmol/g at 1 bar and 273 K was achieved by the carbon activated at 600 °C. The test results also revealed that for carbons with similar volume of small micropores, the one with a high nitrogen content tended to achieve better adsorption performances. [ABSTRACT FROM AUTHOR]

In the present study, N-doped hollow carbon nanospheres (NHCNs) were synthesized with a combined soft template-chemical activation method. Spherical hollow hydrochar was prepared from glucose with the assistance of dual soft templates, and was then chemically activated with KHCO 3 and urea to produce the NHCNs. Effects of urea addition and activation temperature on the NHCNs' physicochemical properties were revealed. The NHCNs were endowed with rich N-doping and developed porosity. The sample activated at 800 °C (NHCN2800) showed an impressive specific surface area of 3234 m2/g. The proposed method could also be extended to the synthesis of N, S co-doped hollow carbon nanospheres. We then investigated CO 2 adsorption performances of the NHCNs. At 25 °C and 1 bar, the best CO 2 uptake of the NHCNs was 4.36 mmol/g; at 20 bar, it increased to a record high level of 23.62 mmol/g. Correlations between textural characteristics/N-doping and CO 2 adsorption at 1/20 bar were analyzed and discussed. The current study indicated that the obtained NHCNs had great potential for applications in both pre- and post-combustion CO 2 capture. [Display omitted] • NHCNs are prepared with a combined soft template-chemical activation method. • The NHCNs demonstrate well-defined hollow spherical structure. • The NHCNs exhibit ultrahigh S BET up to 3234 m2/g. • At 25 °C and 20 bar, CO2 uptake of the NHCNs reaches 23.62 mmol/g. [ABSTRACT FROM AUTHOR]

[Display omitted] • NSCDCs are prepared with novel organic potassium salts as tri-functional activators. • The organic potassium salts act as activator, N source, and S source simultaneously. • The NSCDCs exhibit high surface area and tunable N/S content. • At 25 °C and 20 bar, CO 2 uptake of the NSCDCs reaches 17.29 mmol/g. In the current work, we proposed the use of two organic potassium salts, 4-morpholineethanesulfonic acid (MES) potassium salt and 1,4-piperazinediethanesulfonic acid (PIPES) dipotassium salt, as novel and tri-functional activators for the synthesis of N, S co-doped carbons (NSCDCs). The organic potassium salts served as activator and N/S source at the same time, allowing direct synthesis of NSCDCs with N/S free precursor. In order to verify this hypothesis, N,S free hydrochar derived from glucose was selected as the carbon source. NSCDCs with high and tunable surface area (1673–2235 m2/g), N content (3.44–5.80 wt%), and S content (5.26–8.72 wt%) were obtained. Physicochemical properties of the carbons were mainly decided by potassium salt and activation temperature. The NSCDCs were also investigated for their CO 2 adsorption properties. At 25 °C and 1 bar, high CO 2 uptake of 3.04–3.99 mmol/g was achieved by the carbons. Q st of the NSCDCs was 22.6–28.7 kJ/mol, and CO 2 adsorption selectivity over N 2 was 10.5–17.3 at 25 °C and 1 bar. At 25 °C and 20 bar, CO 2 uptake increased to 11.26–17.29 mmol/g, and exhibited linear dependence on specific surface area. The current work indicated that MES potassium salt/PIPES dipotassium salt could be used as activator for convenient synthesis of NSCDCs as efficient CO 2 adsorbents. [ABSTRACT FROM AUTHOR]

N-doped porous carbons have shown great potential as CO 2 adsorbents. In the current work, we proposed the use of oxamic acid potassium salt (OAPS) as a novel and bifunctional activator for direct synthesis of N-doped porous carbon. OAPS served as both chemical activator and nitrogen source at the same time. N-doped carbons were prepared from different biomass materials including cellulose, agar, and glucose. The yielded carbons exhibited micropores dominated porous structure. Effects of activation conditions and biomass types on the carbons' physicochemical properties were thoroughly studied. As a result, the carbons showed high specific surface area (733–2438 m2/g) and nitrogen content (1.51–3.92 wt%). The presence of narrow micropores and doped nitrogen qualified OAPS activated carbons as efficient CO 2 adsorbents. These carbons demonstrated high CO 2 uptake of 3.91 mmol/g at 25 °C and 1 bar. Respective effects of narrow micropores and N-doping on CO 2 adsorption were also analyzed and revealed. The current study indicated that OAPS could be used as a very convenient and versatile activator for the preparation of N-doped carbonaceous CO 2 adsorbents. [Display omitted] • N-doped carbon is synthesized from cellulose/agar/glucose with OAPS as activator. • OAPS serves as both activator and nitrogen source at high temperature. • The carbons show high S BET (733–2438 m2/g) and nitrogen content (1.51–3.92 wt%). • CO 2 uptake at 25 °C and 1 bar reaches 3.91 mmol/g. [ABSTRACT FROM AUTHOR]

• N, S co-doped carbon spheres are prepared from glucose derived hydrochar. • Thiourea is used as the nitrogen and sulfur sources simultaneously. • Nitrogen and sulfur contents are 4.8–13.0 wt% and 2.4–5.6 wt%, respectively. • The carbon spheres show high surface area of 2581 m2/g. • The maximum CO 2 uptake achieved at 25 °C and 1 bar is 3.4 mmol/g. Synthesis of N, S co-doped carbon has been actively pursued due to their wide applications in different fields including CO 2 adsorption. In the current work, spherical hydrochar was obtained from the hydrothermal carbonization of glucose. The hydrochar was then conveniently converted into N, S co-doped carbon sphere by KHCO 3 activation in the presence of thiourea. The carbon spheres were successfully doped with high contents of nitrogen (4.8–13.0 wt%) and sulfur (2.4–5.6 wt%). The carbon spheres demonstrated specific surface area as high as 2581 m2/g. Influences of various physicochemical properties on CO 2 uptake, adsorption heat, CO 2 /N 2 adsorption selectivity were studied and analyzed. CO 2 uptake of 3.4 mmol/g at 25 °C and 1 bar was achieved by the carbon spheres. The results also showed that CO 2 uptake was mainly decided by volume of small micropores. Nitrogen doping showed positive effects on improving CO 2 uptake and adsorption selectivity, while sulfur doping significantly enhanced interaction strength and improved the adsorption heat. The current work demonstrated a convenient synthesis strategy of N, S co-doped carbonaceous CO 2 adsorbents with controlled morphology. We hope this work will provide new insights into the synthesis and application of heteroatom doped carbons. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfur doped carbon is synthesized from organic potassium salt in one step. • The carbon has high sulfur content of 6.03–9.79 wt%. • The surface area of the carbon reaches 1464 m2/g. • The carbon exhibits high CO 2 uptake of 17.01 mmol/g at 0 °C and 20 bar. In this study, a novel synthesis strategy for sulfur doped carbon (SDC) was developed. Dipotassium anthraquinone-1,8-disulfonate (DAD) was used as the starting material, which produced highly porous SDC after pyrolysis at 600–900 °C. DAD played the roles of carbon and sulfur sources simultaneously, and its decomposition product K 2 SO 4 activated the carbon to generate porosity at high temperature. The yielded SDCs exhibited high level of sulfur doping and high porosity. Effects of pyrolysis temperature on physicochemical properties of the SDCs were studied with various techniques. CO 2 adsorption performances of the SDCs were tested at 0 and 25 °C with pressure up to 20 bar. Influences of sulfur doping on the adsorption capability, isosteric heat, and CO 2 /N 2 selectivity were analyzed and discussed. The experiment results revealed that sulfur doping had positive effects on CO 2 uptake at 1 bar, but adsorption at 20 bar was mainly decided by carbon's total porosity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cesium methanesulfonate is proposed as a bifunctional activator for S-doped carbons. • The carbons show high surface area of 654–2264 m2/g. • S content of the carbons is 6.56–15.13 wt%. • S-doping exhibits positive effects on CO 2 /N 2 selectivity. In the current work, we explored the direct synthesis of S-doped porous carbons employing cesium methanesulfonate as a novel bifunctional chemical activator. The obtained carbons showed high surface area (654–2264 m2/g) and high S content (6.56–15.13 wt%). Effects of activation temperature and cesium methanesulfonate amount on the carbons' properties were also studied. The obtained carbons showed CO 2 uptake of 3.58–4.76 mmol/g at 0 °C and 1 bar. Effects of textural properties and S-doping on CO 2 adsorption performances were discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • CsHCO 3 is used as effective chemical activator to synthesize porous carbons. • The carbons exhibit S BET of 1251–2746 m2/g. • An impressively high CO 2 uptake of 4.64 mmol/g is achieved at 25 °C and 1 bar. • At 25 °C and 20 bar, CO 2 uptake of the carbons reaches 22.12 mmol/g. In the current work, highly porous carbons were prepared from CsHCO 3 activation of glucosamine hydrochloride derived hydrochar. Carbon materials with surface area of 1251–2746 m2/g were obtained at high yield of 42.5–49.9%. The carbons demonstrated remarkable CO 2 adsorption capabilities at both 1 and 20 bar. At 25 °C, an impressively high CO 2 uptake of 4.64 mmol/g was achieved, and it increased to 22.12 mmol/g at 20 bar. The current work shows that CsHCO 3 can be used as a highly effective activator in preparing porous carbons for CO 2 adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous carbons are prepared from the direct pyrolysis of potassium cinnamate. • N-doped porous carbons can be obtained when urea is added. • The carbons show high S BET up to 2198 m2/g. • A high CO 2 uptake of 3.92 mmol/g is achieved at 25 °C and 1 bar. In the current work, honeycomb-like porous carbons were prepared from the direct pyrolysis of potassium cinnamate without the use of any activators or templates. The carbons' surface area reached 2198 m2/g. N-doped porous carbons were also prepared by co-pyrolysis of potassium cinnamate and urea. Effects of the pyrolysis temperature on textural properties and N-doping were studied. CO 2 adsorption performances of the carbons were investigated at 0 and 25 °C. A high CO 2 uptake of 3.92 mmol/g was achieved at 25 °C and 1 bar. [ABSTRACT FROM AUTHOR]