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• Four activated carbon/metal oxides composites (AC/MgO, AC/ZnO, AC/CuO and AC/ZrO 2) were synthesized. • The adsorption performance of AC/MO x composites for three kinds of VOCs (acetone, toluene and methanol) were tested. • ZnO nanoparticles are the most effective for enhancing the VOCs capture performance of activated carbon. • The AC/MO x composites showed strong adsorption to acetone and methanol, but not to toluene. • Adsorption mechanism between VOCs and AC/MO x composites is elucidated by experimental and DFT methods. To enhance the interfacial interaction of activated carbon (AC) with volatile organic compounds (VOCs), the AC surface was modified by depositing metal oxide nanoparticles via an evaporation-induced self-assembly (EISA) method. Taking acetone, toluene and methanol as adsorbates, both dynamic and static VOCs adsorption methods were used to evaluate the adsorption performance of AC and AC/MO x (M = Mg, Zn, Cu and Zr). Compared to pure AC, metal oxide nanoparticles deposition effectively increased the adsorption capacity for acetone and methanol, and AC/ZnO composites showed the best adsorption performance for acetone (415 mg g−1) and methanol (481 mg g−1). In concert with the experiment, a set of systematic theoretical calculations, regarding adsorption energy, adsorption equilibrium distance and charge transfer, were performed to explore the VOCs adsorption mechanism on the metal oxide surface. The adsorption performance can be determined by the Lewis acid-base properties of VOCs-metal oxide systems, the characteristic functional groups and the molecular polarity of VOCs molecules, which paves a new way to develop a novel metal oxide based adsorbent for the VOCs adsorption applications. [ABSTRACT FROM AUTHOR]

• The continuously growing CEI layer exhibits gradually increasing LiF as the main composition in DRX cathode materials. • The significant change of the CEI layer is closely related to loss of lattice oxygen (O2−), the continuous over-reduction of redox-active TMs from the cathode surface, severe TMs dissolution, and the release of CO 2 /O 2 , and irreversible phase transition in surface structures. Li-rich cation-disordered rock-salt oxides (DRXs) are promising candidates for next-generation Li-ion cathode materials due to the demonstrated high capacity (> 300 mAh g−1) by utilizing both transition metal (TM) cations and oxygen anions with a much-widened material design space as compared to conventional layered cathodes, which heavily rely on Co and Ni. However, the serious performance deterioration during long-term cycling impedes their practical applications. Although oxygen loss and associated densified surface layer are responsible for the performance deterioration, these issues are part of the scope of cathode electrolyte interface (CEI) which need further study, including its chemical composition, chemical and electrochemical stability, formation mechanism as well as the effects on battery performance. Through careful monitoring of the CEI evolution of Li 1.2 Mn 0.4 Ti 0.4 O 2 (LMTO) in conventional carbonated-based electrolyte upon charging and discharging, we identify that the continuously growing CEI layer exhibits gradually increasing LiF as the main composition. The significant change of the CEI layer is closely related to loss of lattice oxygen (O2−), the continuous over-reduction of redox-active TMs (e.g. Mn3+, Mn 4+) from the cathode surface, severe TMs dissolution, and the release of CO 2 /O 2 , and irreversible phase transition in surface structures, which eventually cause a fast capacity degradation and voltage decay. This research provides a fundamental interpretation for understanding interfacial stability in this young class of DRX cathode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous carbon and metal heteroatom are implanted into MIL-101 framework. • The 20%Mg@MIL-101/PC has an acetone capture capacity up to 1309 mg g−1 at 288 K. • Porous carbon effectively improves the surface dispersion force of the MIL-101. • Mg replaces the Cr atom to format Mg–O bond in the crystal core. • Adsorption mechanism between acetone and Mg@MIL-101 is elucidated by DFT. The development of highly active and stable adsorbents for volatile organic compounds (VOCs) capture is an efficient solution to address global problems in atmospheric pollution and environmental health. Herein, a metal–organic framework derived adsorbent consisting of metal heteroatom (Mg, Cu and Co) and porous carbon supported on MIL-101 framework is designed to enable high affinity for adsorbing acetone. The doped metal heteroatoms are homogeneously dispersed in the MIL-101/PC octahedron. The modification of doped metal heteroatoms improves the acetone adsorption capacity of the MIL-101/PC composite at low relative pressure. Importantly, the optimized 20%Mg@MIL-101/PC composite not only shows higher surface area (3838 m2 g−1) and pore volume (2.24 mL g−1) than MIL-101/PC, but also creates stronger active adsorption sites for acetone. As a consequence, the acetone adsorption capacity of 20%Mg@MIL-101/PC reaches 1309 mg g−1 at 288 K and 18 bar, and the saturated adsorption capacity decreases by only 12% over 10 adsorption–desorption consecutive cycles. Consequently, quantum chemistry calculation method is performed to better understand the microscopic adsorption behavior of acetone. The results of density functional theory (DFT) calculation show that the introduction of Mg can significantly improve the dipole moment of MIL-101 core and reduce its gap band energy, thus enhancing the electrostatic interaction with acetone molecule. [ABSTRACT FROM AUTHOR]

• The kilogram-level equipment was used to pilot scale tests of pressure swing adsorption. • The effect of the interaction between adsorption and desorption for pressure swing adsorption properties was analyzed. • The mechanism of pressure swing adsorption for different volatile organic compounds was revealed by serious experiments. • The factors influencing nonequilibrium time, effective length and enrichment ratio were analyzed. • The effect of boiling point on desorption performance under different vacuum degrees was demonstrated by experiments. Volatile organic compounds (VOCs) emissions cause serious health problems and environmental pollution, and pressure swing adsorption (PSA) is one of the most promising technologies for VOCs removal and recovery. Commercial activated carbon and three typical VOCs (methanol, acetone and toluene) were selected as adsorbent and adsorbates, and the kilogram-level equipment was used to perform the pilot scale tests in order to study the application of PSA for removing and recycling VOCs in industry. The mechanism and industrial parameters including nonequilibrium time, effective length and enrichment ratio of PSA for removing and recycling VOCs has been studied by PSA experiments, static adsorption experiments, dynamic adsorption experiments, temperature programmed desorption (TPD) experiments and fitting. The results of PSA show that nonequilibrium time and effective length are related to the kinetic diameter, polarity of adsorbates and pore size, surface functional groups of adsorbents, and enrichment ratio is affected by the above factors and the boiling point of adsorbate. The horizontal comparison of three VOCs showed that methanol and acetone molecules with smaller kinetic diameter and greater polarity only need shorter effective length to removed completely by PSA. At low vacuum, the desorption performance is related to desorption activation energy (methanol 18.62 kJ/mol < acetone 22.20 kJ/mol < toluene 41.15 kJ/mol). At high vacuum, the desorption performance will be improved while the boiling point of adsorbate is lower than the temperature of fixed-bed. Based on this mechanism, the enrichment ratio of acetone can reach 2.1 under the same conditions, so that the recovery ratio of acetone became the highest among these three VOCs. This result provides new opportunities for the removal and recovery of VOCs gases. [ABSTRACT FROM AUTHOR]

• Oxygen and nitrogen co-doped porous carbon/MgO (ONPC@MgO) composites were synthesized. • Acetone is captured by O/N functional groups and MgO by monolayer adsorption at low pressure. • Acetone is adsorbed on the surface of carbon and MgO by multilayer adsorption at high pressure. • Adsorption mechanism between acetone and ONPC@MgO composites is elucidated by experimental and DFT methods. The amount of anthropogenic volatile organic compounds (VOCs) emission keeps increasing worldwide, and it urges the development of VOC emission reduction technology. Efficient and environmentally friendly adsorption technology is receiving more interest, and carbon-based materials have attracted enormous attention for VOC capture. However, the poor adsorption capacity and cycling stability still hinder their application. Moreover, the mechanism of adsorption behavior between functionalized carbon surfaces and VOCs has not been investigated in detail. Herein, we report a sustainable and cost-effective method for the anchoring of the MgO nanoparticle onto O/N co-doped porous carbon derived from waste biomass (denoted as MgO@ONPC). The optimized 7%MgO@ONPC composite exhibited an exceedingly high acetone adsorption capacity (859 mg g−1 at 25 °C, 18 kPa) and excellent cycling stability (95.2% capacity retention over 10 cycles). Acetone dynamic breakthrough tests showed that the adsorption capacity of 7%MgO@ONPC composite at 10% breakthrough level (10% BT) and 100% BT was 384 and 508 mg g−1, respectively (in terms of PC: 3.9 × 10−3 and 5.2 × 10−2 mol kg−1 Pa−1, respectively). Isotherm model fitting and quantum chemistry calculation studies indicated O/N functional groups and MgO nanoparticles can significantly improve the acetone monolayer adsorption at low relative pressures due to hydrogen bonds and electrostatic interaction. Highly active MgO nanoparticles and pore structure characteristics are found to be determinative factors for acetone adsorption at high relative pressure. [ABSTRACT FROM AUTHOR]

Highlights • N-rich nanoporous carbon with C 3 N-type was synthesized. • The methanol adsorption mainly depends on the porosity structure at high pressure. • The methanol adsorption is determined by the functional groups at low pressures. • The adsorption mechanism between methanol and nitrogen groups is elucidated. Abstract The N-rich nitrogen (25.7%) porous carbon with high surface area was prepared by using N-rich ZIF-8 as a template and precursor and urea as a secondary nitrogen source. Simple pyrolysis of the ZIF-8/urea composite leads to N-rich carbon with C 3 N-type stoichiometry. The content and type of nitrogen functional groups can be tunable by the pyrolysis temperature. The resulting carbons stand out by a highly polarizable microporous structure and thus high affinity for methanol adsorption. The experimental results indicate that the microporous structure of porous carbon is the determinant of methanol adsorption at high pressure, whereas at low pressure, the methanol adsorption dominantly depends on the nitrogen functional groups. To more deeply investigate the interactions between the methanol molecules and carbon framework, we performed the theoretical analysis regarding the adsorption isotherms, binding energy and atomic partial charge using the GCMC and DFT methods. The methanol adsorption capacity is determined by the electrostatic interaction at low relative pressures due to the nitrogen functional groups enhancing the electrostatic potential of carbon surface. While the dispersive interaction becomes dominant at high relative pressures, and thus the methanol adsorption mainly depends on the porosity structure. [ABSTRACT FROM AUTHOR]