Strong Influence of Amine Grafting on MIL-101 (Cr) Metal–Organic Framework with Exceptional CO₂/N₂ Selectivity

Abstract

Matérial Institut Lavoisier (MIL)-101, one of the metal–organic frameworks containing numerous coordinatively unsaturated sites, as well as high specific surface area, was synthetized under different protocols for CO2 adsorption and separation from N2. To improve its CO2 adsorption capacity, different amounts [10, 25, and 40 wt % of tetraethylenepentamine (TEPA)] were grafted to the parental MIL-101. Results revealed that TEPA-MIL-101 (40 wt %) showed one of the highest CO2 adsorption capacities (i.e., 3.76 mmol g–1 at 298 K at 1 bar) among existing MIL-101 and its modified moieties. This amount was 1.56 times greater than parental MIL-101 (in spite of having superior textural properties), which adsorbed 2.41 mmol g–1 CO2 at the same operational conditions. This can be attributed to the presence of polar functional groups in the porous structure of MIL-101 that enhance the interaction between CO2 active sites on the adsorbent surface. Isosteric heat of adsorption of CO2 and N2 on TEPA-MIL-101 (40 wt %) were 35 and 18 kJ mol–1, respectively, based on the temperature-dependent form of the Freundlich model in the Clausius–Clapeyron equation. Ideal adsorption solution theory (IAST) was used for determination of CO2/N2 selectivity for a binary gas mixture, including 15% CO2 and 85% N2 at 298 K and at 1 bar. TEPA-MIL-101 (40 wt %) showed an exceptional CO2/N2 selectivity of 220. Adsorption kinetics study demonstrated that the Avrami model was the best model for fitting the experimental data, which denotes that more than one pathway exists in CO2 and N2 adsorption.

Sequential Solid‐State Transformations Involving Consecutive Rearrangements of Secondary Building Units in a Metal–Organic Framework (MOF)

“…Though the sorption capacity is somewhat small, it is worth to note that the remarkable selectivity of CO 2 /N 2 far exceeds those of many reported MOFs, such as ZnF(daTZ) (120), [26] UTSA-85a (62.5), [27] and TEPA-MIL-101 (40 wt %) (220). [28] Overall, the impressive adsorption selectivity indicates that the framework of UPC-601 can form stronger interactions with CO 2 and C 2 H 2 than CH 4 or N 2 , making it potential candidate for CO 2 capture from flue gas and natural gas purification.…”

Adsorbing Volatile Organic Chemicals by Soluble Triazine-Based Dendrimers under Ambient Conditions with the Adsorption Capacity of Pyridine up to 946.2 mg/g

“…VOCs, including aromatics, alkanes, amines, and oxygenated or halogenated hydrocarbons [ 4 , 5 , 6 ], are often produced by chemical and pharmaceutical industries [ 7 , 8 , 9 ]. Porous materials currently used for adsorbing VOCs are zeolites (Zs) [ 10 , 11 , 12 ], activated carbons (ACs) [ 13 , 14 , 15 , 16 ], polymeric resins (PRs) [ 17 , 18 , 19 , 20 ], and metal-organic frameworks (MOFs) [ 21 , 22 , 23 , 24 ]. In these systems, a pre-drying column to remove the moisture of absorbed chemicals is generally required to maintain the adsorbing efficiency [ 24 ], which is an additional cost for VOC adsorption.…”

Research progress in metal–organic frameworks (MOFs) in CO2capture from post-combustion coal-fired flue gas: characteristics, preparation, modification and applications

“…The regeneration energy was also low due to its low heat capacity, which was better than amine grafted silica and amine aqueous solution. Pirzadeh et al 98 grafted different amounts of tetraethylenepentamine (TEPA) to the parental MIL-101. The results showed that TEPA-MIL-101 (40 wt%) had one of the largest CO 2 adsorption capacity (3.76 mmol g −1 at 298 K, 1 bar) with 1.56 times higher than that of MIL-101 among the existing MIL-101 and its modified components, as well as the good CO 2 cyclic adsorption stability, as shown in Fig.…”