First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.

It is demonstrated that the fluorine-modified porous graphene membrane has excellent selectivity for CO2/N2 separation by using molecular dynamic (MD) simulations. We also investigated in detail the mechanism of the fluorine-modified porous graphene membrane for CO2/N2 separation by using first-principles simulations. We find that the diffusion barriers for CO2 and N2 to pass through the pore-22 (with 22 carbon atoms drilled out) graphene membrane are relatively small, which indicates that the pore-22 has a low selectivity for CO2/N2 separation. After fluorine modification, the diffusion barrier for CO2 to pass through decreases to 0.029 eV, while the diffusion barrier for N2 greatly increases to 0.116 eV. Therefore, N2 gets more difficult, while CO2 gets easier to penetrate through the fluorine-modified pore-22. The fluorine-modified pore-22 porous graphene shows a great enhancement of selectivity for CO2/N2 separation, which is consistent with the MD results. Our studies show that first-principles simulations can be well used to understand the MD results and propose an economical and efficient means of separating CO2 from N2, which may be useful for designing new concept membranes for gas separation, like CO/N2 and SO2/N2 separations.

The fabrication of carbon (C) doped hexagonal boron nitride (h-BN) has attracted more and more attention due to its widespread applications. A novel method of constructing custom-designed C doped h-BN via CO molecules interaction with the vacancy defect h-BN is demonstrated in this paper using density functional theory (DFT) calculations. The reaction process consists of the CO-vacancy recombination and extra O removal by CO; thus, C doped h-BN is formed without introducing additional defects. According to the population analysis, the charge transfer between CO and the defect h-BN is found to be important for the reaction. The proposed method is not only theoretically feasible but also has a relatively low reaction energy barrier, so the doping process can be easily achieved. Such a doping method provides a promising route toward on-demand tailoring of electrical and magnetic properties of diverse C doped BN nanostructures.

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Replacing petroleum-based chemicals with biomass-based alternatives is becoming more and more important for the development of a low-carbon economy around the world. The latest life cycle assessment displayed that partially replacing phenol with biobased lignin in the process of synthesizing phenolic resin adhesives used in wood panels industry can remarkably reduce carbon emissions and negative environmental impact. The macromolecular structure of lignin is similar to that of phenolic resin and the basic structure unit is similar to that of the phenol, thus endowing it with the potential to substitute phenol and reduce the release of formaldehyde in the preparation process of phenolic resin. Importantly, the lignin-based adhesive exhibits improved performance and reduced cost compared with the petroleum-based adhesive due to the reduced adding amount of petroleum-based volatile components. However, the intrinsic large steric hindrance, structural heterogeneity, and low activity of the natural lignin limit its further application in the adhesive. Many researchers have developed the activation methods such as physical modification, chemical modification, and biological modification to overcome these issues. The different modification of the lignin and their application in the adhesive area are mainly summarized here. Besides, the modification methods and the curing mechanism are also discussed.

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