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It's acknowledged that surface chemical and pore structure of adsorbent are main parameters to determine adsorption results. Herein, we prepared zeolitic imidazolate frameworks‐8 (ZIF‐8) with different average sizes (50, 120, and 2200 nm) and demonstrated their specific surface area and pore volume decreased with increasing particle size. ZIF‐8 (ZN) exhibits a large specific surface area (1626.4 m2 g−1) and total pore volume (1.088 mL g−1), but it has been shown to lack the non‐specific adsorption capacity for the adsorbate. Carbonization at 800 °C is proved to be an effective method to expose massive surface nitrogen‐containing functional groups and adjust the aperture to an appropriate pore size range for derived porous carbon of ZIF‐8 (ZCN). High nitrogen content (18.7 at. %) greatly improves the affinity for CO2 and Volatile Organic Compounds (VOCs), as explained by the density functional theory (DFT) calculation results. Meanwhile, particle size influences the pore‐forming results after carbonization directly. Among them, ZC50 generates a certain amount of narrow micropore in range of 0.7–1.0 nm, located in the optimal pore size range of CO2 adsorption calculated by Grand canonical Monte Carlo (GCMC) simulation, thus possessing the largest CO2 adsorption capacity (4.03 mmol g−1 at 25 °C). Besides, ZC120 exhibits more superior mesopore structure that could strengthen multilayer adsorption for VOCs. [ABSTRACT FROM AUTHOR]

The porous carbon material is widely used as acetone adsorbent. The low‐cost, facile and efficient synthesis method of porous carbon material is of great significance to the removal of acetone. Potassium citrate, a common organic salt, was self‐activated in the current study at the temperatures of 600–900 °C to form porous carbons (KAC−X) with rich microporous structures. The KAC−X showed excellent specific surface area (763–2100 m2 g−1) and oxygen content (5.95–16.29 wt%). The sample obtained at the temperature of 900 °C showed promising acetone adsorption capacities of 8.33 mmol g−1 (15 °C) and 7.27 mmol g−1 (25 °C), respectively. The acetone adsorption results were well fitted by the Langmuir‐Freundlich and Freundlich models. Moreover, the influence of physical structure and oxygen functional group on the acetone adsorption performance was explored. The results showed that: (1) one of the main methods for promoting the acetone adsorption capacity is to increase the specific surface area; (2) the other method is to increase the optimal pore volume, and the optimal pore size is 2–5 times of the acetone molecule diameter; (3) carboxyl and carbonyl groups can significantly increase the adsorption affinity between acetone molecule and KAC−X, and play an auxiliary role on the acetone adsorption. This study provides guidance for the facile synthesis of porous carbons from organic salt for the sake of acetone adsorption. [ABSTRACT FROM AUTHOR]

Nitrogen‐enriched porous carbon material with large specific surface area is of great demand in various applications. Herein, CuCl2 is adapted as a mild activator to transform the mixture of soybean meal and melamine cyanurate into a novel type of nitrogen‐enriched hollow porous carbon microspheres with well‐defined hierarchically structure. Excitingly, this mild activation agent not only helps generating porous structure, but also helps increasing the nitrogen content (mainly pyrrolic‐N) of products. The product NPC‐800‐4 exhibits the highest specific surface area (1672.45 m2 g−1) while a pretty high nitrogen content (13.09 at%). The NPC‐800‐4 sample performs the largest toluene and acetone adsorption capacity (818.46 mg g−1 and 758.87 mg g−1 respectively). Furthermore, Grand canonical Monte Carlo (GCMC) and density functional theory (DFT) calculations prove that the introduction of nitrogen functional groups can heighten the polarity of carbon framework and the electrostatic interaction, thus enhance the acetone adsorption capacity. [ABSTRACT FROM AUTHOR]

To investigate the effects of oxygen‐containing functional groups on the adsorption of volatile organic compounds (VOCs) with different polarity, oxygen‐rich porous carbon materials (OPCs) were synthesized by heat treatment of glucose/potassium oxalate material. The carbon material had a large specific surface area (1697 m2 g−1) and a high oxygen content (18.95 at.%). OPC exhibited high adsorption capacity of toluene (309 mg g−1) and methanol (447 mg g−1). The specific surface area and total pore volume determined the adsorption capacity of toluene and methanol at the high‐pressure range, while the oxygen‐containing groups became the main factor affecting the methanol adsorption at the low‐pressure range due to the hydrogen bond interaction through the density functional theory (DFT) calculations. This study provides an important hint for developing a novel O‐doped adsorbent for the VOCs adsorption applications and analyzing the role of oxygen‐containing groups in the VOCs adsorption under the low‐pressure range. [ABSTRACT FROM AUTHOR]

Graphical abstract Hierarchy in zeolite pore architecture greatly affected heavy metal adsorption of nickel. Highlights • The effects of mesopore architecture in hierarchical zeolites on heavy metal removal were investigated. • Adsorption of Ni2+ was dependent on pore geometry due to the phyllosilicate nanosheet formation. • Adsorption of Pb2+ or Cu2+ was dependent on cation exchange determined by the framework composition. • Zeolite crystallinity, mesoporosity, and adsorbate pH values affected Ni2+ uptake. Abstract Zeolites have been widely used for heavy metal removal due to their high cation exchange capacity and surface sorption properties. However, the empirically determined adsorption capacity trend of Pb2+ > Cu2+ > Ni2+ was not well understood. Herein, we discovered that the adsorption of Ni2+ by zeolites was greatly influenced by hierarchical pore geometry, while the adsorption of Pb2+ or Cu2+ was dependent on cation exchange determined by the framework composition. This difference in adsorption mechanisms is manifested through the systematic study of heavy metal adsorption using low-silica LTA and FAU zeolites with different mesopore architectures and compositions. Synthesizing mesoporous zeolite A of MLTA-P using proline mesoporogen considerably enhanced the Ni2+ adsorption capacity to more than twice of that of conventional zeolite A synthesized without organics, while the adsorption capacities for Cu2+ and Pb2+ were almost unaltered at ∼170 and 510 mg/g. The study on the effect of zeolite synthesis time and adsorbate pH value revealed the significant influence of zeolite crystallinity, surface hydroxyl group, and hierarchical pore architecture on the Ni2+ uptake. The MLTA-P zeolite showed higher stability against pH variation in acid range and remarkably enhanced uptake in alkaline conditions, reaching 218 mg/g at a pH of 11. The full characterization of the adsorbent by scanning electron microscopy and X-ray photoelectron spectroscopy indicated the involvement of the surface reaction forming Ni phyllosilicate nanosheet species during the nickel metal removal process in which transport limitation played a crucial role. The uptake kinetics and isotherms could be perfectly reflected by a pseudo-second-order rate equation and the Langmuir model, confirming the nature of chemisorption. [ABSTRACT FROM AUTHOR]

The porous carbon is considered to be one of the most suitable materials for volatile organic compounds (VOCs) adsorption and separation. Revealing the adsorption behavior and molecular interaction mechanism is of great significance for the preparation and synthesis of porous carbon adsorbents. Herein, we investigated detailed mechanistic effects of graphitization degrees and surface oxygen heteroatoms of porous carbon on their benzene and ethanol adsorptive separation performance by combining experiments and theoretical calculations. The results show that graphitized carbon surface has a stronger van der Waals interaction with benzene molecules compared to the disordered carbon surface, and thus exhibit a higher benzene adsorption performance and benzene/ethanol selectivity. While the introduction of oxygen functional groups enhances electrostatic affinity of porous carbon surface, resulting in higher ethanol adsorption capacity and ethanol/benzene selectivity under the entire pressure range. Subsequent theoretical calculations studied the adsorption behaviors of benzene and ethanol molecules in porous carbon models (with different graphitization degrees and oxygen contents) from the perspective of the weak interactions, and found the different molecular configurations of benzene and ethanol is the main leading cause of their different adsorption preferences. This study provided mechanistic insights on how the graphitization degrees and oxygen heteroatoms affected the capture and separation properties of porous carbon, which would further provide a rational alternative strategy in the preparation and synthesis of porous carbons for the effective gas mixture capture and separation. • The vital role of graphitization degrees and surface oxygen heteroatoms on VOCs adsorptive separation is proved. • Provide a molecular perspective on the adsorption behavior of VOCs in porous carbons. • The intrinsic enhancement mechanism in adsorption and separation process was clarified. • Provide a rational alternative strategy in preparation and synthesis of porous carbons. [ABSTRACT FROM AUTHOR]

• The vital role of oxygen content in determining VOCs adsorption is proved. • The carboxyl groups favors the VOCs adsorption and separation the most. • The remarkable capacity is mainly attributes to the strong electrostatic interaction. • The aggregation of methanol molecules are responsible for the high selectivity. • No obvious synergistic effect between oxygen functional groups was found. Heteroatoms doping brings a burgeoning class of adsorbents for the removal of volatile organic compounds (VOCs). It is of great importance to reveal the molecular interaction and adsorption mechanism on account of the nanoscale nature of adsorption. Herein, we combined adsorption experiments and theoretical calculations (using porous carbon as adsorbent and graphene as computational model) to reveal the influence of doping oxygen atoms on the surface heterogeneity and the VOCs adsorption performance, and to investigate the synergistic effect of oxygen-containing functional groups. The results show that oxygen doping can significantly change the charge distribution and improve the adsorption and separation of methanol and acetone (the selected representative of VOCs). Among various oxygen-containing functional groups, the carboxyl doped surface displays the largest theoretical adsorption capacity of methanol (36.74 mmol/g) and acetone (18.35 mmol/g) and the highest selectivity (16.11 at 0.1 kPa). Specifically, the doped oxygen containing groups significantly changed the charge distribution on the carbon surface (e.g., –0.50 to 0.43 e for carboxyl group), and enhanced the electrostatic interaction between the surface and VOCs molecules, thereby increasing the adsorption capacity. Moreover, the stronger binding energy between the oxygen-functionalized surface and methanol contributed to the preferential adsorption of methanol on the oxygen active sites, leading to the aggregation of methanol molecules, which is responsible for the high selectivity. Meanwhile, no obvious synergistic effect between oxygen functional groups was found. This study provides fundamental understanding of the role of oxygen-containing groups toward VOCs adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • The VOCs adsorption isotherms of alkali metal-doped carbon were calculated. • The VOCs adsorption capacity on PC-LiO increased by 924 and 29 times compared with PC (0.2 kPa). • The VOCs adsorption capacity on PC-Rs are determined by the pore structure at relatively high pressure. • The intrinsic mechanisms of alkali metal groups to VOCs adsorption were clarified. • Provide theoretical guidance for preparation of VOCs adsorbents. The doping of alkali metal groups (LiO-, NaO- and KO-) into porous carbons (PC) for acetone and methanol adsorption were studied for the first time by Grand Canonical Monte Carlo (GCMC) simulation and Density Function Theory (DFT). The results indicate that all alkali metals groups can significantly improve the methanol and acetone adsorption capacity at relatively low pressure (0.2 kPa). Especially the methanol and acetone adsorption capacity on PC-LiO increased by 924 and 29 times compared with PC, respectively. These results are mainly attributed to the stronger adsorption energy and electrostatic interaction of PC-LiO on VOCs molecules than that of PC. At relatively high pressure, the alkali metals groups have no obvious effect on the methanol and acetone adsorption capacity, but are determined by the pore structure due to the pore-filling adsorption mechanism. Besides, the methanol/acetone selectivity of PC-LiO is much higher than that of PC, indicating that the LiO-doped PC can improve methanol and acetone separation. The above results show that alkali metal-doped porous carbon has been proved to be one of the promising adsorbents for methanol and acetone adsorption capacity at relatively low pressure, and provides an effective alternative strategy for the design and screening of VOCs adsorbents. [ABSTRACT FROM AUTHOR]