Adsorption Interface-Induced H...F Charge Transfer in Ultramicroporous Metal–Organic Frameworks for Perfluorinated Gas Separation

Abstract

Fluorinated electron gases (F-gases) are widely used in semiconductor manufacturing because of their unique plasma reactivity with silicon-based semiconductor materials. However, the low conversion efficiency of these F-gases in the plasma process makes the vent gases contain a certain concentration of F-gases, which causes environmental pollution and global warming. In this study, three ultramicroporous metal–organic frameworks M3(HCOO)6 (M = Co, Ni, Mn) were prepared for the separation and purification of F-gases through H...F interaction-induced charge transfer on the pore surface. Impressive F-gas adsorption capacities and record breakthrough selectivities for NF3/N2, CF4/N2, and SF6/N2 mixtures were achieved in M3(HCOO)6 MOFs. Density-functional theory (DFT) calculations and grand canonical Monte Carlo (GCMC) simulation studies demonstrated that the adsorption-induced charge exchange between the F atom in F-gases and the H atom in HCOO– accounts for the high performance of F-gases/N2 separation. Systematic experimental investigations including equilibrium gas adsorption, instant adsorption rates, and dynamic breakthrough experiments also confirmed the efficient performance of M3(HCOO)6 MOFs for F-gas capture.

Destructive Adsorption of Nitrogen Trifluoride (NF3) Using M-MOF-74 with Open Metal Sites

“…Owing to Zn-MOF-74’s low adsorption capacity and weak adsorption affinity toward NF 3 , its selectivity for NF 3 /N 2 is only 2.8 (Figure d) at 298 K and 100 kPa. Co-MOF-74 displays the highest NF 3 /N 2 selectivity among the four MOFs studied and outperforms several materials previously reported in the literature for NF 3 /N 2 selectivity, namely, POPTrB-8F (5.7), Co 3 (HCOO) 6 (19.2), Mn 3 (HCOO) 6 (20.0), Ni 3 (HCOO) 6 (30.0), SBMOF-1 (21.0), Ni-MOF (35.8), NH 2 –Ni-MOF (32.4), PC-750 (61.4), and others. The adsorption curve indicates Co-MOF-74 has a stronger affinity for NF 3 at low pressures, with an adsorption capacity of up to 54.0 cm 3 g –1 (2.41 mmol g –1 ) at 10 kPa.…”

Enhanced azeotropic C2ClF5/C3F8 separation by TMA+ exchanged MFI zeolites for ultrapure fluorine electronic gas

“…Considering the establishment of permanent microporosity and suitable pore aperture size, C 2 ClF 5 and C 3 F 8 adsorption isotherms were collected at 298 K for ZSM-5 and TMAZ-Xs (Figure 3E,F environment, which enhanced F…H/Cl…H van der Waals force interactions between C 2 ClF 5 and the abundant hydrogen atoms lining the pore surfaces due to TMA + enrichment. 38 The pristine ZSM-5 zeolite exhibits large pore apertures ($6.5 Å, Figure 2E) and poor hydrogen atoms that are more match with the relatively larger tortuosity. 39 The diffusion through the sinusoidal channel is invariably lengthier than through straight channels, owing to the greater tortuosity of the sinusoidal channels, which forces molecules to collide and rebound more frequently, thereby reducing the molecular diffusion rate.…”

High throughput screening of pure silica zeolites for CF4 capture from electronics industry gas

“…Fluorine-containing cleaning gases mainly include CF 4 , hexafluoroethane (C 2 F 6 ), sulfur hexafluoride (SF 6 ), and other perfluorocarbons. 17 Porous adsorbents such as zeolites, [18][19][20][21] metal-organic frameworks, [22][23][24] carbon nanotubes, [25][26][27][28] and amorphous activated carbon 29 are commonly used for adsorbing and separating fluorine components in gas mixtures. For example, Skarmoutsos et al 25 have investigated the adsorption and separation performance of carbon nanomaterials and metal-organic frameworks in CF 4 -SF 6 and CF 4 -N 2 fluid mixtures using Monte Carlo and molecular dynamics simulations.…”