document: Gas sorption, storage and separation in carbon materials are mainly based on physisorption on the surfaces and particularly depend on the electrostatic and dispersion (i.e., vdW) interactions. The former can be tuned by introducing charge variations in the material, and the latter by chemical substitution. The strength of the interaction is determined by the surface characteristics of the adsorbent and the properties of targeted adsorbate molecule, including but not limited to the size and shape of the adsorbate molecule along with its polarizability, magnetic susceptibility, permanent dipole moment, and quadrupole moment. Li et al. summarise the adsorption-related physical parameters of many gas or vapour adsorbates, and herein Table 1 we show a few of those of interest, H2, N2, CO, CO2, CH4, NH3, SO2 and H2S [90]. For instance, an adsorbent with a high specific surface area is a good candidate for adsorption of a molecule with high polarizability but no polarity. Adsorbents with highly polarised surfaces are good for adsorbate molecules with a high dipole moment. The adsorbents with high electric field gradient surfaces are found to be ideal for the high quadrupole moment adsorbate molecules [91]. Normally, the binding or adsorption strength with a carbon nanostructure is relatively low for H2 and N2; intermediate for CO, CH4 and CO2; and relatively high for H2S, NH3 and H2O. Thus, surface modifications, such as doping, functionalization and improving the pore structure and specific surface area of nanocarbons, are important to enhance gas adsorption. For this purpose, graphene offers a great scope for tailor-made carbonaceous adsorbents.
extractive_keyphrases: adsorbate molecule adsorbate molecules adsorbent adsorbents carbon materials ch4 chemical substitution co co2 doping enhance gas adsorption functionalization gas or vapour adsorbates graphene h2 h2o h2s improving the pore structure and specific surface area of nanocarbons introducing charge variations in the material molecule n2 nh3 physisorption so2 surface modifications
abstractive_keyphrases: carbonaceous adsorbents electrostatic and dispersion (i.e., vdw) interactions gas sorption, storage and separation high quadrupole moment adsorbate molecules nanocarbons