CO2 Adsorption on the N- and P-Modified Mesoporous Silicas

Abstract

SBA-15 and MCM-48 mesoporous silicas were modified with functionalized (3-aminopropyl)triethoxysilane) (APTES) by using the post-synthesis method, thus introducing N- and P-containing groups to the pore surface. The structure of the newly synthesized modifiers (aldimine and aminophosphonate derivatives of (3-aminopropyl)triethoxysilane) and their grafting onto the porous matrix were proved by applying multinuclear NMR and FTIR spectroscopies. The content of the grafted functional groups was determined via thermogravimetric analysis. The physicochemical properties of the adsorbent samples were studied by nitrogen physisorption and UV–Vis spectroscopy. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The modified silicas displayed an enhanced adsorption capacity compared to the initial material. The 13C NMR spectra with high-power proton decoupling proved the presence of physically captured CO2. A value of 4.60 mmol/g was achieved for the MCM-48 material grafted with the Schiff base residues. The total CO2 desorption was achieved at 40 °C. A slight decrease of about 5% in CO2 adsorption capacities was registered for the modified silicas in three adsorption/desorption cycles, indicating their performance stability.

Engineering of Silica Mesoporous Materials for CO2 Adsorption

“…The preparation procedure included firstly the synthesis of a Schiff base (denoted as SAPTES) from the reaction of APTES and furfural as described in our recent publication [40]. The procedure and the NMR and IR data are provided in the Supplementary Material.…”

“…Therefore, based on our previous experience, the synthetic path applied included the reaction of DOPO with a Schiff base (denoted as SAPTES) derived from APTES. The preparation of SAPTES has been reported in our previous paper [40]. SAPTES was obtained quantitatively from the reaction of APTES with furfural in toluene.…”

“…All the modified samples displayed a 1.5-to 2-fold increase in the capacity for CO 2 adsorption in comparison to the initial materials. The MCM-48 material grafted with Schiff base residues was more efficient in the CO 2 capture experiments than the analogous SBA-15 sample or those bearing aminophosphonate fragments [40]. Microporous polycarbazole, which possessed an electron-rich scaffold, showed an excellent uptake capacity for carbon dioxide and good selectivity toward CO 2 over N 2 [41].…”

“…Besides amino modification, the introduction of other functionalities onto the sorbent surface could also enhance the CO 2 adsorption capacity and/or selectivity [39]. In our recent study [40], novel (3-aminopropyl)triethoxysilane (APTES) derivatives with tailored structures, which included an azomethine group conjugated with a furanyl ring or an aminophosphonate fragment, were used to modify the pore surface of MCM-48 and SBA-15 silicas. All the modified samples displayed a 1.5-to 2-fold increase in the capacity for CO 2 adsorption in comparison to the initial materials.…”

One-Pot Synthesis of Rubber Seed Shell-Derived N-Doped Ultramicroporous Carbons for Efficient CO2 Adsorption

“…So far, various solid CO 2 adsorbents have been designed and exploited, such as metal organic frameworks MOFs [ 7 ], zeolites [ 8 ], mesoporous silica [ 9 ], covalent organic framework COFs [ 10 ], porous organic polymers POPs [ 11 ], and N-doped porous carbons NPCs [ 12 ]. Remarkably, N-doped porous carbons stand out due to their low-cost preparation, high specific surface area, excellent thermal and chemical properties, designable pore structure, and easy surface functionalization [ 13 ].…”