Calcium-Based Metal–Organic Framework for Efficient Capture of Sulfur Hexafluoride at Low Concentrations

Abstract

Sulfur hexafluoride (SF6), which has a greenhouse effect of 228 000 times more terrible than carbon dioxide, has attracted increasing attention. Its efficient capture, especially from the mixtures with low SF6 concentrations, is urgently needed while challenging. Herein, we use a calcium (Ca)-based metal–organic framework (MOF; SBMOF-1) with multiaromatic ring-functionalized channels to achieve a record selectivity as high as 727 for an industrially relevant SF6/N2 mixture (volume concentration of SF6: 0.03%) at 298 K and 1 bar. Grand canonical Monte Carlo simulations and density functional theory calculations identified that SF6 molecules were energy-favorably trapped in the functionalized MOF channels by the strong interactions between the channel walls and six fluorine atoms on SF6. Excellent breakthrough results accompanied with good stability and regenerability recommend its promising application for practical SF6 capture from low-concentration SF6 mixtures, which also provides a new benchmark for SF6/N2 separation.

Separation ofCH4/N2by an ultra‐stable metal–organic framework with the highest breakthrough selectivity

“…It can be seen that the kinetic adsorption rate of NKMOF‐8‐Me for N 2 and CH 4 is higher than that of Al‐CDC, but the kinetic N 2 /CH 4 selectivity is low. Based on the above experimental results, it can be further shown that smaller the pore size of material is, the slower the diffusion of guest molecules in the pores will be, which may lead to an obvious kinetic N 2 /CH 4 separation effect and relatively low breakthrough selectivity 75–83 . Additionally, we compared with the results in several zeolites in literature.…”

“…14 Based on the above experimental results, it can be further shown that smaller the pore size of material is, the slower the diffusion of guest molecules in the pores will be, which may lead to an obvious kinetic N 2 /CH 4 separation effect and relatively low breakthrough selectivity. [75][76][77][78][79][80][81][82][83] Additionally, we compared with the results in several zeolites in literature. For example, the diffusion time constants of MCHA (pore size: 3.8 Å) and ZK-5 (pore size: 3.9 Å) for N 2 and CH 4 were 0.02918 and 0.03672 1/min (N 2 ) and 0.004326 and 0.008870 1/min (CH 4 ) at 298 K respectively, with the corresponding kinetic selectivities of 6.7 and 4.1 respectively, 38,84 which are lower than those in this work.…”

Enhancing CH4 Capture from Coalbed Methane through Tuning van der Waals Affinity within Isoreticular Al-Based Metal–Organic Frameworks

“…The sample was regenerated using high-purity He (30 mL min –1 ) continuous purging of the fixed bed for 2 h under room conditions. The breakthrough adsorption capacity of CH 4 and N 2 and the corresponding CH 4 /N 2 breakthrough selectivity were also obtained based on the following equation: where Q CH 4 and Q N2 represent the breakthrough adsorption capacities of CH 4 and N 2 (cm 3 (STP) g –1 ), respectively; q and q i represent the total volumetric flow rate and volumetric flow rate (mL min –1 ) of gas i at time t , respectively; t i represents the breakthrough adsorption time (min) of guest molecules; V d represents the column dead volume (mL); S breakthrough represents the breakthrough selectivity; and X i represents the molar fractions of i guest molecules in the bulk phase.…”

Amino-Functionalized Microporous MOFs for Capturing Greenhouse Gases CF4 and NF3 with Record Selectivity

“…Pressure swing adsorption (PSA) based on adsorbents has shown advantages for gas separation due to its operational simplicity and energy efficiency. − The adsorbent is the key to the PSA process, which is supposed to possess high capacity and selectivity . It has been reported that SF 6 capture and SF 6 /N 2 selectivity are high. − However, the values of CF 4 sorption and CF 4 /N 2 selectivity are generally very low. ,, Also, the separation of CF 4 /N 2 and NF 3 /N 2 is more challenging than that of SF 6 /N 2 due to the smaller kinetic diameters of CF 4 and NF 3 (4.6 Å for CF 4 , 3.6 Å for NF 3 , 5.1 Å for SF 6 ) …”