Supporting Information

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1 Supporting Information Nitrogen-doped coal tar pitch based microporous carbons with superior CO 2 capture performance Dai Yu, Jun Hu, Lihui Zhou *, Jinxia Li, Jing Tang, Changjun Peng, and Honglai Liu School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai , China lhzhou@ecust.edu.cn

2 Calculation of isosteric heat of CO 2 adsorption The isosteric heat of adsorption was calculated using the Clausius-Clapeyron equition: 1 P T T ln = H P R T T ads where P i is pressure for isotherm i, T i is temperature for isotherm i, R is J K -1 mol -1 ; which was used to calculate isosteric heat of adsorption ( H ads ) of a gas as a function of the quantity of gas adsorbed. Pressure as a function of the amount of CO 2 adsorbed was determined by the Toth model for the isotherms. m ( ) 1/ ( 1+ B P) Q B P Q= where Q = moles adsorbed, Q = moles adsorbed at saturation, P = pressure; B and t = constants; which can be used to calculate the pressure P. 1/ t t Calculation of CO 2 /N 2 selectivity: 1. Initial slope method The CO 2 /N 2 selectivity by initial slope method was calculated by the ratio of the initial slopes in the Henry region of the adsorption isotherms. 2. Ideal adsorbed solution theory (IAST) The pure component isotherms of CO 2 measured at 298 K were fitted with the dual-site Langmuir model while the pure component isotherms of N 2 measured at 298 K were fitted with the single-site Langmuir model. 2 The single-site Langmuir model is defined as: q b p i = qi, sat 1 + b i p The dual-site Langmuir model is defined as: b p bj p q= q + q b p i i, sat j, sat bi p Where, q is molar loading of adsorbate (mmol g -1 ); q sat is the saturation loading (mmol g -1 ); b is Langmuir constant (Pa -1 ); p is bulk gas phase pressure of the species (Pa); i and j are referring to the two distinct adsorption sites. j

3 For the CO 2 :N 2 (15:85) binary mixtures, which is typical of flue gases, the IAST selectivity can be calculated using the following equation: S= q1 / q2 p / p 1 2 Figure S1. TEM images of CTP (a-b) and N-CP (c-d).

4 Figure S2. TEM images of N-AC (a b), N-AC (c d), and N-AC (e f).

5 Figure S3. (a b) NLDFT pore size distributions of the samples (N-AC-x-y) prepared at different conditions. Figure S4. High resolution Fe 2p XPS spectra of N-AC-x-y samples.

6 Figure S5. Five cycles of CO 2 adsorption on N-AC at 298 K without any heat treatment. Figure S6. CO 2 and N 2 uptake of (a) N-AC and (b) N-AC up to 1 bar at 298 K. The selectivity of (c) N-AC and (d) N-AC for CO 2 over N 2 isotherms obtained from the initial slope method at 298 K.

7 Figure S7. CO 2 and N 2 adsorption isotherms measured at 298 K and their IAST equation fit curves of N-AC (a b) and N-AC (c d). Table S1. The yield, content of different N species, and CO 2 /N 2 selectivity for CTP, N-CP, and N-AC-x-y samples. Sample Yield (%) Total N (wt%) a Pyridinic N Pyridonic N Quaternary N Oxidized N CO 2 /N 2 (%) b (%) b (%) b (%) b Selectivity c CTP N-CP d - N-AC N-AC N-AC N-AC N-AC a Obtained by C, H, N elemental analysis. b Measured by XPS. c Calculated by initial slope method. d This N species refers to pyridine-n-oxide. The rest of N species in N-CP are chemisorbed N-oxide (406.5 ev, 79.8%) and -NO 2 N (408 ev, 5.0%).

8 Table S2. Comparison of the CO 2 adsorption capacity (25 o C and 0 o C, 1 bar) of carbonaceous adsorbents. CO 2 uptake (mmol g -1 ) Adsorbents Ref. 25 o C 0 o C N-AC This work N-AC This work NC UC C N NAC-Rb(600) 4.88 ~ SU NC AK CPC NOMC-K a NAC AC a-ndc HNP SC a Measured at 0.95 bar.

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