Interaction of CO₂ and CH₄ with Functionalized Periodic Mesoporous Phenylene–Silica: Periodic DFT Calculations and Gas Adsorption Measurements

Abstract

Non-functionalized and functionalized periodic mesoporous phenylene-silicas (Ph-PMOs) with different kinds of amine groups were prepared and their capacity to uptake CO2 and CH4 molecules were experimentally evaluated considering biogas upgrading. It was found that aminopropyl groups grafted to the free silanols of the Ph-PMO displayed the highest selectivity for CO2 gas, adsorbing 26.1 times more CO2 than CH4 at 25 C. The interaction effect of the surface of these materials with the CO2 or CH4 molecules was obtained through the calculation of the Henry constants, and the adsorption mechanisms involved were elucidated from density functional theory calculations. The good synergy between experimental gas adsorption and computational studies suggests that the latter can be used to guide the experimental synthesis of more effective materials. Thus, our computational studies were extended to PMOs with other functional groups having different polarity for predicting interaction energies with CO2 and thus identifying the most promising candidates for experimental synthesis.

Hydrogen-bond supramolecular hydrogels as efficient precursors in the preparation of freestanding 3D carbonaceous architectures containing BCNO nanocrystals and exhibiting a high CO2/CH4 adsorption ratio

“…Thus, the CO 2 -CH 4 selectivities calculated for BCNO MBG1 and BCNO MBG2 from their respective k H values were again remarkable, in the upper range of figures found for some of the most efficient adsorbents reported to date -e.g. see data inTable 2for porous carbons, POFs, zeolites and MOFs 55,60,61,64,68,72,73,74,75,76,77. 4.…”

Selectivity for CO2 over CH4 on a functionalized periodic mesoporous phenylene-silica explained by transition state theory

“…Thus far, selectivity for CO 2 /CH 4 separation for different functionalized PMOs has been evaluated by using experiments [30,31], while the CO 2 and CH 4 adsorption mechanisms involved in this materials were clarified using periodic density functional theory (DFT) calculations [30]. In fact, as we have observed, experimental gas adsorption data and computational studies are in good agreement and such DFT results proved also useful to guide the preparation of more efficient PMO materials.…”

“…Additionally, Ph-PMOs display a narrow distribution of both meso-and molecular-scale periodicities; a clear advantage for adsorbate diffusion within the pore channels. Moreover, we have seen [30,31] that the modification of the Ph-PMO with amine groups allows the optimization of their properties for the separation of CO 2 /CH 4 , by improving the interaction with the CO 2 molecule. Recently, we demonstrated that aminopropyl groups grafted to the free silanols of Ph-PMO promote selectivity for CO 2 /CH 4 separation making the resulting APTMS@Ph-PMO so far the most selective of all PMOs applied in this field, at 25 °C adsorbing 26.1 times more CO 2 than CH 4 , as determined by the ratio of Henry constants [30].…”

Recent Advances in the Preparation and Applications of Organo‐functionalized Porous Materials

“…demonstrated that amine groups could be functionalized in the PMOs through mononitration with nitric acid in the presence of sulphuric acid, followed by the reduction with tin chloride and HCl. The amine‐functionalized samples showed higher selectivity for the adsorption of CO 2 molecules in comparison with the CH 4 molecules . The same group also manipulated the amine‐functionalized PMOs for the formation of dialkylated amine through the microwave‐assisted approach.…”