Diamine-functionalized metal–organic framework: exceptionally high CO₂capacities from ambient air and flue gas, ultrafast CO₂uptake rate, and adsorption mechanism

Enhanced CO2 adsorption capacity of amine-functionalized MIL-100(Cr) metal–organic frameworks

“…The heat of carbon dioxide adsorption of EN-MIL-100(Cr) and MMEN-MIL-100(Cr) approaches 80 kJ mol -1 at zero coverage, a value nearly 20 kJ mol -1 higher than that obtained for MIL-100(Cr), which suggests a strong and selective interaction of CO2 with the alkylamines functionalities, and compares well with previously reported data obtained for other alkylamine-functionalized metal-organic frameworks. 31,33,[38][39][40] This high binding energy for CO2 in amine-functionalized metal-organic frameworks must be attributed to a chemisorptive type interaction, akin to the chemisorption mechanisms that are operative for CO2 separation using aqueous alkanolamines. The adsorption heat decreases rapidly with increasing loading, indicating that the number of amine groups that strongly adsorb CO2 is considerable less than the total number of amine molecules grafted to the framework.…”

“…39 Solid sorbents with high adsorption enthalpies have the advantages of high selectivity and capacity but material regeneration is a concern. 40,60 To ensure the regenerability of the materials, we further performed some regeneration and CO2 adsorption cycling measurements using a combined temperature swing and nitrogen purge approach. Following activation of the material, a flow of CO2 was introduced into the furnace at 308 K for 60 minutes.…”

“…[29][30][31][32][33][34][35][36][37][38][39][40] Two major strategies are envisaged to achieve this goal: (i) the direct use of an amine-based bridging ligands to generate the three-dimensional newtwork, 29,30,32 or (ii) postsynthetic approaches that covalently modify a bridging ligand or graft an alkylamine functionality onto a coordinatively unsaturated metal center. 31,[33][34][35][36][37][38][39][40] This last approach has been used by different authors during the last years resulting generally in an improvement of CO2 selectivity and an enhancement in CO2 capacity, especially at low pressures.However, for MOFs to be practically useful as adsorbents for either CO2 capture from flue gas or natural gas upgrading, a number of aspects need to be carefully evaluated in addition to capacity and selectivity. Chemical and thermal stability are also two very important parameters for MOFs to be considered for CO2 adsorption.…”

Strong binding site molarity of MOFs and its effect on CO2 adsorption

“…A hydrogen-bonded complex involving two carbamic acid moieties was formed which results in 2:2 amine:CO 2 stoichiometry with higher capacity and weaker binding energy than the 2:1 stoichiometry observed in most amine-functionalized adsorbents [10]. Overall, both unsaturated metal cations or alklyamines inside the pores of MOFs can be considered as strong binding sites for CO 2 adsorption, resulting in high CO 2 adsorption capacity at low pressure range [1,8,9].Many studies have investigated the nature of binding site and its effect on CO 2 adsorption at low pressure for a specific MOF [5e12]. However, there lacks effort to compare CO 2 adsorption on various MOF with strong binding sites.…”

Understanding Small‐Molecule Interactions in Metal–Organic Frameworks: Coupling Experiment with Theory

“…400 ppm at room temperature), [ 34,35 ] properties that are maintained even after water exposure. [ 36 ] All of these attributes have brought understanding of small-molecule interactions in materials with open metal sites to the forefront of MOF chemistry. One of the most well-studied MOFs to date is M 2 (dobdc), alternatively known as M-MOF-74 or CPO-27-M, where M = Mg, Mn, Fe, Co, Ni, Cu, or Zn ( Figure 2 ).…”