Excellent CO2 Adsorption Capacity Research Articles

Ultra-microporous biochar-based carbon adsorbents by a facile chemical activation strategy for high-performance CO2 adsorption

The new adsorption-enhanced compressed CO2 energy storage technology uses high-performance adsorbents to adsorb and store CO2 in low-pressure tanks, reducing vessel costs while significantly increasing energy storage density. In this paper, porous biochar with excellent CO2 adsorption capacity is prepared by carbonization combined with KOH chemical activation using pine nut shells, which can be used for the energy storage system. The influence of pore structure is revealed by changing the activation temperature. The results show that the activity of KOH is moderate at 700 °C, which can promote the formation of ultramicropores. The specific surface area of the obtained porous biochar is 1027 m2·g−1, the distribution center of ultramicropores is about 0.65 nm, and the microporosity can up to 91.7%, which is very suitable for CO2 adsorption under atmospheric pressure and room temperature. The CO2 adsorption capacities are 6.05 mmol·g−1 and 3.96 mmol·g−1 at 1 bar, 273 K and 298 K with the pore volume is only 0.56 cm3·g−1. The material also has a low value of isosteric heat of adsorption about 25 kJ·mol−1. These findings suggest that pine nut shells can be used to design highly porous biochar for the system of new adsorption-enhanced compressed CO2 energy storage.

Two-dimensional oxalamide based isostructural MOFs for CO2 capture

Metal-organic frameworks (MOFs), members of porous crystalline materials, have been investigated for CO2 capture and separation from various exhaust gas mixtures. An essential element to build new MOFs with improved CO2 capture and separation abilities is to understand the influence of functional groups on the surface of pores on gas adsorption properties. Oxalamide groups have two amide moieties that feature a strong affinity to CO2. In this study, three new isostructural Co(II), Zn(II), and Cd(II)-MOFs have been synthesized by using 3,3'-(oxalylbis(azanediyl))dibenzoic acid (3-OADAH2) ligand which has a CO2-philic oxalamide group. To the best of our knowledge 3,3'-(oxalylbis(azanediyl))dibenzoic acid (3-OADAH2) was used as a linker for the first time. X-ray diffraction analysis shows that the MOFs possess two-dimensional (2D) structures and the layers interact with each other through hydrogen bonds. Co-, Zn-, and Cd-3-OADA exhibit an excellent CO2 adsorption capacity of 8.87 ​wt% (45.15 ​cm3/g), 8.40 ​wt% (42.76 ​cm3/g), and 7.93 ​wt% (40.37 ​cm3/g) at 273 ​K and 3.98 ​wt% (20.27 ​cm3/g), 4.74 ​wt% (24.15 ​cm3/g), 3.68 ​wt% (18.72 ​cm3/g) at 298 ​K under 1 ​bar with isosteric heat of adsorption values (Qst) of about 34, 25, and 33 ​kJ/mol, respectively. This work opens a new opportunity for the development of functionalized 2D-MOFs with high CO2 capture capacity.

Polyethyleneimine-modified layered double hydroxide/SBA-15 composites: A novel kind of highly efficient CO2 adsorbents

The SBA-15-supported polyethyleneimine (PEI)-modified layered double hydroxides (xLDH-yPEI/SBA-15) were prepared by the in situ coprecipitation method, and their CO2 adsorption performance and involved mechanisms were studied. After loading of PEI and LDH on the surface of SBA-15, the composite materials still maintained an ordered two-dimensional hexagonal porous structure. The optimal CO2 adsorption capacity (2.01 mmol/g) of 40LDH-2PEI/SBA-15 at 50 °C was 1.88 times larger than that (1.07 mmol/g) of SBA-15. Such an excellent CO2 adsorption capacity of 40LDH-2PEI/SBA-15 was associated with its high BET surface area, abundant basic sites, and fast adsorption kinetics. The regeneration efficiency of 40LDH-2PEI/SBA-15 was still 94% after 11 recycles. We are sure that the SBA-15-supported PEI-modified LDH materials are good performance adsorbents for the adsorption of carbon dioxide.

Interlayer Expansion in a Layered Metal-Organic Framework Enhances CO2 Capture and CO2 /N2 Separation.

Developing efficient CO2 adsorbent materials and technologies is significant to reduce the increasing greenhouse gases concentration in the atmosphere. Herein, a layered MOF with a porous kagomé lattice (kgm), which owned three phases (kgm-1, kgm-2, and kgm-3) via interlayer expansion, was evaluated as a promising CO2 capture and separation material by using grand canonical Monte Carlo simulations. Results showed that the interlayer expansion provided additional pore volume, which played a considerable role in CO2 adsorption and separation. The CO2 adsorption capacity and CO2 /N2 selectivity followed the sequence kgm-3>kgm-2>kgm-1, and kgm-3 exhibited an excellent CO2 adsorption capacity of 8.7 mmol g-1 at 1 bar with a CO2 /N2 selectivity of 130.3 at 20 bar and 298 K. Gas distribution analysis showed that CO2 and N2 are adsorbed only in the channels in kgm-1, whereas they could be adsorbed between layers in kgm-2 and kgm-3 due to the interlayer expansion. The adsorption heat and interactions between CO2 and frameworks were analyzed to elucidate the effect of interlayer expansion. Results of this work highlighted that appropriate interlayer expansion can be an effective approach for framework adsorbents to improve CO2 capture ability and separation performance at the same time.

From Hazardous Waste to Green Applications: Selective Surface Functionalization of Waste Cigarette Filters for High-Performance Robust Triboelectric Nanogenerators and CO2 Adsorbents.

This article reports a novel and rational approach to convert waste cigarette filters (CFs), one of the largest sources of ocean pollution, into high-performance triboelectric nanogenerators (TENGs) and efficient CO2-capturing adsorbents. CFs are plasticized cellulose acetate, which take several years to degrade. To revalorize these fibers, selective amine surface functionalization is performed (10PAL-20T-CFs). For the proof of concept, when the modified fibers are employed in a TENG, it could generate an output voltage (96.63 V) and current (9.37 μA) that are, respectively, 43 and 8 times higher than those obtained employing the pristine CFs for the nanogenerator. The proposed TENG displays an instantaneous peak power of 3.75 mW, which is higher than that of many recently reported TENGs made from cellulose materials. Moreover, the TENG displayed outstanding durability to humidity and high-performance stability when it is subjected to cyclic loading (i.e., 12,000 cycles of loading-unloading). A 9 cm2 TENG could effectively light up 100 or more colored light-emitting diodes when it is manually pressed. Finally, the modified filter fibers show an excellent CO2 adsorption capacity of 1.93 mmol/g, which is 9.2 times higher than that obtained using the pristine fibers. These results demonstrate that hazardous wastes such as CFs can be upcycled into valuable resources.

Amine functionalized mesocellular silica foam as highly efficient sorbents for CO2 capture

A series of amine-functionalized CO2 sorbents were synthesized by grafting mono- and tri-amine substituted trialkoxysilanes on mesocellular siliceous foam (MCF) via a facile wet grafting method. The effect of amine type, amine loading level, and porous structure of silica on the CO2 adsorption performance was investigated. MCF silica with a three-dimensional (3D) interconnected porous structure was found to be suitable for preparing amine-grafted sorbents. Tested at 25 °C and 0.15 bar of CO2, the mono- and tri-amine grafted MCFs exhibited a fast adsorption rate and excellent CO2 adsorption capacity of 1.71 mmol/g for mono-amine and 2.07 mmol/g for tri-amine, which was much higher than amine grafted PQ and SBA-15 with a 2D porous structure, and the amine grafted silica sorbents prepared in previous studies. The large pore volume and pore size coupled with superior interconnectivity of MCF enable more surface silanol groups available and accessible for amino silanes, leading to a high amine loading level and excellent amine dispersion on the silica surface, which enhances both the CO2 adsorption capacity and adsorption rate of the developed sorbents. Cyclic adsorption–desorption tests confirmed the excellent stability of the amine grafted MCF.

Zeolitic imidazolate framework-8 modified cathode promotes microbial electrosynthesis from carbon dioxide

Microbial electrosynthesis (MES) is an electrochemical reduction technology through which microorganisms attached to a cathode are driven by electricity to reduce carbon dioxide (CO2) into industrial chemicals. However, the limited contact time with biocatalysts affects the performance of MES because of low CO2 solubility. In this study, zeolitic imidazolate framework-8 (ZIF-8) particles with different pore diameters modified cathodes were prepared. Results showed that the ZIF-8 modified electrode obtained the maximum acetate production rate (0.13 g L−1 d−1), which was 1.4 times that of bare CF, and the accumulated acetate concentration reached 4.04 ± 0.1 g L−1 within 30 days. Brunauer–Emmett–Teller test and CO2 adsorption characteristic evaluation indicated that ZIF-8 had a high specific surface area and an excellent CO2 adsorption capacity. Scanning electron microscopy and microbial community analysis revealed that ZIF-8 modified electrodes were beneficial to biofilm formation and increased the enrichment of Acetobacterium and Arcobacter. Therefore, CO2-adsorbing materials modified electrodes are effective in improving the performance of MES.

Rational design of 3D carbon nitrides assemblies with tunable nano-building blocks for efficient visible-light photocatalytic CO2 conversion

g-C3N4 is an appealing non-metal photocatalyst for CO2 reduction, while it shows unsatisfactory performance due to poor CO2 adsorption ability and deficient collection of photo-excited charges, but its efficiency greatly relies on the effective bulk and surface separation of photoexcited charge carriers. To address the challenges, we elaborately design Ag nanoparticles decorated 3D ordered g-C3N4 assemblies based on a synergistic route of Ag-induced supramolecular tailoring and assembling followed by thermal polymerization. The 3D structural topology of the nano-units for g-C3N4 can be altered from 2D orderly stacked nanosheets to 1D twisty g-C3N4 nanotubes by varying the amount of Ag(I). Moreover, the band structures and nitrogen vacancies can also be well-regulated. As supported by experimental and DFT calculation results, ACNNT-2 demonstrates excellent CO2 adsorption capacity, superior light harvesting ability, efficient charge separation and more localized charge density distribution, which can effectively decrease the energy barrier for COOH* intermediate and boost the CO* desorption, resulting in a superior photocatalytic selectivity. Consequently, in sharp contrast to BCN, the ACNNT-2 manifests a markedly improved CO generation rate of 145.5 μmol g−1h−1 under visible-light irradiation, reflecting an 18-fold enhancement together with a CO selectivity of 89%. This strategy provides a profound insight into the multiscale modulation of g-C3N4 photocatalysts with enhanced efficiency.

Ordered Mesoporous Boron Carbon Nitrides with Tunable Mesopore Nanoarchitectonics for Energy Storage and CO2 Adsorption Properties.

Porous boron carbon nitride (BCN) is one of the exciting systems with unique electrochemical and adsorption properties. However, the synthesis of low‐cost and porous BCN with tunable porosity is challenging, limiting its full potential in a variety of applications. Herein, the preparation of well‐defined mesoporous boron carbon nitride (MBCN) with high specific surface area, tunable pores, and nitrogen contents is demonstrated through a simple integration of chemical polymerization of readily available sucrose and borane ammonia complex (BAC) through the nano‐hard‐templating approach. The bimodal pores are introduced in MBCN by controlling the self‐organization of BAC and sucrose molecules within the nanochannels of the template. It is found that the optimized sample shows a high specific capacitance (296 F g−1 at 0.5 A g−1), large specific capacity for sodium‐ion battery (349 mAg h−1 at 50 mAh g−1), and excellent CO2 adsorption capacity (27.14 mmol g−1 at 30 bar). Density functional theory calculations demonstrate that different adsorption sites (B—C, B—N, C—N, and C—C) and the large specific surface area strongly support the high adsorption capacity. This finding offers an innovative breakthrough in the design and development of MBCN nanostructures for energy storage and carbon capture applications.

Amine-Modified Biochar for the Efficient Adsorption of Carbon Dioxide in Flue Gas

Biochar-based carbonaceous adsorbents are gaining interest due to their high availability, ease of modification, and low cost; however, they show limited adsorption of CO2 in flue gas due to common textural properties. In this study, TEPA-modified biochar was used to prepare a solid amine adsorbent for the efficient capture of CO2 in flue gas. First, the porous biochar was prepared with FeCl3, Mg(NO3)2, and H2O (g) as activators and walnut shells as carbon sources. Next, the biochar was modified with TEPA to obtain a solid amine adsorbent. Porous texture properties and sample surface functional groups were characterized, and we measured the adsorption CO2 of the amine-modified biochar in a breakthrough adsorption device. Results showed that biochar has a large specific surface area (744.38 m2 g−1), a total pore volume of 1.41 cm3 g−1, and a high mesoporous volume ratio (82.7%). The high pore volume provided a more efficient support space for loading tetraethylenepentamine (TEPA). The adsorbent had an excellent CO2 adsorption capacity, corresponding to 2.82 mmol g−1, which increased to 3.31 mmol g−1 and kept water resistance at 10% H2O (g) simulated flue gas (SFG). The FTIR analysis showed that H2O (g) inhibited urea production after cyclic adsorption. Therefore, solid amine adsorbent created by amine-modified biochar has potential advantages in its application for capturing CO2 in SFG.

From polyvinyl chloride waste to activated carbons: the role of occurring additives on porosity development and gas adsorption properties

Conversion of waste plastic to carbon materials has been considered as a potential approach for plastic recycling. In this study, polyvinyl chloride (PVC) plastic, one of the most widely used polymers, was used as a single precursor to prepare porous carbons via chemical activation process. The results showed that KOH activation followed by acid washing was an effective strategy to recover all calcium- and up to 92% of titanium-based compounds, the main metal additives in PVC, in the form of soluble salt. Those metal additives in PVC acted as a type of hard template, which benefit the development of microporosity and carbon dioxide (CO2) adsorption. Textural characterization demonstrated that the prepared carbons possessed high surface area and pore volume of up to 2507 m2/g and 1.11 cm3/g, respectively. At 0 °C and 100 kPa, the PVC-derived carbon, PH_73, which has highest ultra-micropore volume among all samples, exhibited excellent CO2 adsorption capacity of 6.90 mmol/g and high CO2/N2 selectivity. Converting the non-degradable PVC into high-quality porous carbon materials could be considered as a potential strategy for plastic waste recycling.

Mesoporous alumina-supported layered double hydroxides for efficient CO2 capture

A novel kind of CO2 solid adsorbents (xLDH/MA, x is the loading of LDH) was prepared by loading of layered double hydroxides (LDH) on the mesoporous alumina (MA) support. The LDHs in xLDH/MA were evenly distributed on the surface of MA. xLDH/MA possessed a large BET surface area (278–378 m2/g), narrow pore-size distribution (4.37–6.23 nm), and a highly crystalline framework. Among all of the samples, 30LDH/MA showed an excellent CO2 adsorption capacity at 50 °C (1.56 mmol/g), which was 1.55 times larger than that of unmodified MA. Due to the synergistic effect between MA and LDH, 30LDH/MA exhibited a higher surface area and a more amount of adsorption sites, which were the main factors improving its CO2 adsorption performance. The adsorption process of CO2 on xLDH/MA was dominated by the chemical adsorption, and the adsorbed CO2 was mainly stored in the form of carbonate. In addition, the 30LDH/MA composite material showed fast adsorption kinetics and good regeneration efficiency. We believe that such a kind of porous alumina-supported layered double hydroxides would have a great potential in the applications for the adsorption of CO2.

Densification and pelletization of porous boron nitride fibers for effective CO2 adsorption

Due to the rich pore structure and high specific surface area, porous boron nitride (BN) shows good performance in gas adsorption. Densification and pelletization of porous BN powder into pellets with high porosity, desired porous structure and good mechanical strength is highly required for its practical CO2 capture. Here, we demonstrate the high-yield synthesis of BN pellets via a dichloromethane-assisted precipitation, extrusion and pyrolysis process. Without using any polymer binders, porous BN fibers with high aspect ratios are crisscrossed with each other and assembled into BN pellets with uniform cylinder-shaped macroscopic morphology. After pelletization, the bulk density and mechanical strength of BN pellets have been effectively improved. The prepared BN pellets have high specific surface area of 1098.9 m2/g, and pore volume up to 0.47 cc/g, in which the micropore volume is as high as 93.6% of the total pore volume, thus making the pellets show excellent equilibrium and dynamic CO2 adsorption capacity. Especially, due to the extremely rich ulta-micropores, the CO2/N2 selectivity of BN pellets is calculated to be 20.6 (at 1 bar), higher than the previously reported BN adsorbents. The present work demonstrates a new idea for the pelletization of BN materials, which provides the possibility to further expand the application fields of BN materials.

Synthesis of palm sheath derived-porous carbon for selective CO2 adsorption.

Biomass-derived porous carbons are regarded as the most preferential adsorbents for CO2 capture due to their well-developed textural properties, tunable porosity and low cost. Herein, novel porous carbons were facilely prepared by activation of palm sheath for the highly selective separation of CO2 from gas mixtures. The textural features of carbon materials were characterized by the analysis of surface morphology and N2 isotherms for textural characterization. The as-prepared carbon adsorbents possess an excellent CO2 adsorption capacity of 3.48 mmol g−1 (298 K) and 5.28 mmol g−1 (273 K) at 1 bar, and outstanding IAST selectivities of CO2/N2, CO2/CH4, and CH4/N2 up to 32.7, 7.1 and 4.6 at 298 K and 1 bar, respectively. Also, the adsorption evaluation criteria of the vacuum swing adsorption (VSA) process, the breakthrough experiments, and the cyclic experiments have comprehensively demonstrated the palm sheath derived porous carbons as efficient adsorbents for practical applications.

Facile One-Pot Synthesis of Zn/Mg-MOF-74 with Unsaturated Coordination Metal Centers for Efficient CO2 Adsorption and Conversion to Cyclic Carbonates.

Bimetallic metal-organic frameworks (MOFs) containing two different inorganic metal nodes exhibited enhanced properties in CO2 adsorption and catalytic conversion compared with the corresponding monometallic MOFs. In this work, the novel bimetallic Zn/Mg-MOF-74 with different ratios of Zn/Mg was synthesized successfully by a facile one-pot method. Powder X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy/transmission electron microscopy, N2/CO2 adsorption/desorption, and CO2/NH3-temperature-programmed desorption techniques thoroughly characterized the structure, morphology, and physicochemical properties of Zn/Mg-MOF-74. Besides the excellent CO2 adsorption capacity (128.3 cm3/g at 273 K and 1 bar), Zn0.75Mg0.25-MOF-74 also showed efficient catalytic activity for the cycloaddition reaction of CO2 and epoxides to cyclic carbonates with outstanding yield and selectivity all over 99% under solvent-free and mild conditions (60 °C, 0.8 MPa), outperforming the mechanical combination of Zn-MOF-74 and Mg-MOF-74 with the same metal contents, indicating the synergistic effect of two adjacent metals in bimetallic MOF-74. In addition, the Zn0.75Mg0.25-MOF-74 catalyst could be recycled for at least five runs and possess good versatility to various substrates. Finally, a feasible mechanism of the catalytic reaction was proposed. Thanks to the high surface area, affinity toward CO2, and accessibility of multiple active sites of the unsaturated metal centers as active Lewis acid sites and O atoms from Zn-O and Mg-O as Lewis basic sites, efficient chemical fixation of CO2 to cyclic carbonates was obtained over the Zn0.75Mg0.25-MOF-74 catalyst. The present facile synthesis and application of a robust bimetallic MOF catalyst offered a competitive avenue for the integration of CO2 adsorption and CO2 catalytic conversion.

CO2 adsorption performance of nitrogen-doped porous carbon derived from licorice residue by hydrothermal treatment

For high-value and environmentally friendly utilization of industrial herbal waste, a series of licorice residue-derived porous carbons were prepared with nitrogen-doped hydrothermal carbonization and KOH activation. The N-doped porous carbon activated at 600 °C exhibited excellent CO2 adsorption capacity (6.43 mmol/g at 0 °C and 1 bar, 3.89 mmol/g at 25 °C and 1 bar), high CO2/N2 selectivity (21.3), and high initial isosteric adsorption heat (28.7 kJ/mol). The excellent CO2 adsorption of the sorbent can be ascribed to its high microporosity and nitrogen content. At 0 °C and 1 bar, the ultramicropore volume below 0.7 nm contributes almost equally with the N content. However, the N content plays a dominative role at higher temperature or lower pressure. N content, especially N-5 content, performs a sound correlation with the CO2 adsorption capacity under ambient condition.

Controllable Synthesis of 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) Benzene-Based MOFs

The growing interest in metal–organic frameworks (MOFs) in both industrial and scientific circles has increased in the last twenty years, owing to their crystallinity, structural versatility, and controlled porosity. In this study, we present three novel MOFs obtained from the 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) benzene (TIBM) organic linker. The formed TIBM crystal powders were characterized by scanning electron microscopy (SEM) to estimate the morphology of the particles, powder X-ray diffraction (XRD) to confirm the crystal structure, Brunauer–Emmett–Teller (BET) method for structural analysis, and thermogravimetric measurements to examine the thermal stability. The TIBM-Cu MOF showed excellent CO2 (3.60 mmol/g) adsorption capacity at 1 bar and 298 K, because of the open Cu site, compared to TIBM-Cr (1.6 mmol/g) and TIBM-Al (2.1 mmol/g). Additionally, due to the high porosity (0.3–1.5 nm), TIBM-Cu MOF showed a considerable CO2/N2 selectivity (53) compared to TIBM-Al (35) and TIBM-Cr (10).

Nitrogen and sulfur co-doped porous carbons from polyacrylonitrile fibers for CO2 adsorption

BackgroundsAdsorption by adsorbents is accepted as a promising technology that can efficiently separate CO2 from flue gas. Optimal adsorption performance can be obtained by specific solid adsorbents with excellent CO2 adsorption capacity. MethodsIn this work, N, S co-doped porous carbons were synthesized from polyacrylonitrile fiber by a facile synthesis process i.e. hydrothermal treatment followed by KOH activation. N, S enriched hydrochar was obtained after hydrothermal treatment of polyacrylonitrile fiber and ammonium sulfide. Further KOH activation of hydrochar obtained N, S co-doped carbons with advanced porous structure. Significant findingsThis series of sorbents has the highest CO2 uptake of 3.37 and 5.23 mmol g−1 at 1 bar, 25 °C and 0 °C, respectively. Detailed investigation revealed that the mutual effects of narrow microporostiy, N and S content are responsible for the CO2 uptake of these adsorbents. Additionally, these adsorbents also show various good CO2 capture properties such as excellent recyclability, reasonable CO2/N2 selectivity, moderate heat of adsorption, fast adsorption kinetics, and good dynamic adsorption capacity. These findings suggest that N, S co-doped porous carbons derived from polyacrylonitrile fiber are potential promising sorbents for CO2 capture.

Excellent Electrochemical Performance of La0.3Sr0.7Fe0.9Ti0.1O3-δ as a Symmetric Electrode for Solid Oxide Cells.

Solid oxide cells (SOCs) can switch between fuel cell and electrolysis cell modes, which alleviate environmental and energy problems. In this study, the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi 91) perovskite is innovatively used as a symmetric electrode for solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). LSFTi 91 exhibits a pure perovskite phase in both oxidizing and reducing atmospheres, and the maximum conductivity in air and 5% H2/Ar is 150 and 1.1 S cm-1, respectively, which meets the requirement of the symmetric electrode. The polarization resistance (Rp) at 1.5 V is as low as 0.09 Ω cm2 in the SOEC mode due to the excellent CO2 adsorption capacity. The current density can reach 1.9 A cm-2 at 1.5 V and 800 °C, which is the highest electrolytic performance in the reported single-phase electrodes. LSFTi 91 also exhibits eminent oxygen reduction reaction and hydrogen oxidation reaction (ORR and HOR) activities, with Rp of 0.022 and 0.15 Ω cm2 in air and wet H2, respectively. The peak power density of SOFC could reach 847 mW cm-2 at 800 °C. In addition, good reversibility is confirmed in the cyclic operation of SOFC and SOEC.

In situ simultaneous chemical activation and exfoliation of carbon quantum dots for atmospheric adsorption of H2S and CO2 at room temperature

Herein, novel nitrogen-doped nanoporous carbons possessing 2.63 at.% N and high porosity were prepared using nitrogen-rich carbon quantum dots (N-CQDs) via a facile chemical activation. To this end, after performing the hydrothermal process on the raw materials, chemical activation was carried out by various KOH/N-CQDs ratios (2:1 to –4:1), resulting in unique micro-mesoporous structures (i.e., HNAC samples). In this approach, a large surface area (1477 m2g−1) and pore volume (1.05 cm3g−1) were obtained, where the micropore volume was increased by decreasing the KOH/N-CQDs ratio, activation time and augmenting the activation temperature, that caused considerable adsorption at 1 bar. It is worth mentioning that mesopores could be generated by condition optimization that led to higher adsorption at high pressure. Due to their large surface area and high nitrogen loading, the HNAC samples demonstrated excellent H2S and CO2 adsorption capacity at ambient conditions (9.28 mmolg−1 for H2S and 4.28 mmolg−1 for CO2 at 1 bar and 25 °C) and at higher pressures (18.0 mmolg−1 for H2S and 6.20 mmolg−1 for CO2 at 10 bar and 25 °C). According to the significant performance of the prepared nanosorbents along with stable cyclic adsorption-desorption performance, the HNACs are proposed as promising adsorbents with outstanding adsorption.