Hydrophobic pillared square grids for selective removal of CO₂ from simulated flue gas

Abstract

Capture of CO2 from flue gas is considered to be a feasible approach to mitigate the effects of anthropogenic emission of CO2. Herein we report that an isostructural family of metal organic materials (MOMs) of general formula [M(linker)2(pillar)], linker = pyrazine, pillar = hexaflourosilicate and M = Zn, Cu, Ni and Co exhibits highly selective removal of CO2 from dry and wet simulated flue gas. Two members of the family, M = Ni and Co, SIFSIX-3-Ni and SIFSIX-3-Co, respectively, are reported for the first time and compared with the previously reported Zn and Cu analogs.

A Fine-Tuned Fluorinated MOF Addresses the Needs for Trace CO2 Removal and Air Capture Using Physisorption

“…17,30,31 Considerately, in addition to enabling the MOF pore system characteristics, contracted squareshaped channels with a periodically aligned proximal fluorine moieties, two other parameters were considered for the design and construction of the looked-for hydrolytically stable MOF for carbon capture. Specifically, we elected: i) to employ the Ni(II) as the octahedrally-coordinated metal node since the SIFSIX-3-Ni offers a shorter M-F bond distance (d M-F = 1.99(5) Å) 32 then the SIFSIX-3-Cu (d M-F = 2.12(1) Å) 17 and thus prone to express the requisite water vapor tolerance, and ii) to substitute the (SiF 6 ) 2-pillar with an appropriate fluorinated inorganic pillar, offering a relatively stronger coordination bonds and the adequate nucleophilicity that can preclude the observed phase change in the SIFSIX-3-Cu, associated with the water molecule introduction within the Cu(II) coordination sphere. 31 Accordingly, the (NbOF 5 ) 2-was explored as a potential pillar to replace the original inorganic pillar, (SiF 6 ) 2-, due its associated distinct attributes: (i) the larger size of Nb 5+ imparts a longer Nb-F bond length (1.899(1) Å) than the Si-F bond (1.681(1) Å), signifying the plausible reduction in the distance between the pendant proximal fluorine moieties within the channel; (ii) the higher nucleophile behavior of the (NbOF 5 ) 2-is anticipated to enhance the water stability of the resultant MOF ( Figure 1).…”

Effect of ring rotation upon gas adsorption in SIFSIX-3-M (M = Fe, Ni) pillared square grid networks

“…SIFSIX-3-Ni was prepared using the previously reported procedure 33 by dissolving 10 mmol of pyrazine (pyz) and 5 mmol of NiSiF 6 ·6H 2 O in 30 ml of methanol and heating at 75 °C for 3 days .…”

“…A new isostructure of the SIFSIX-3-M family, 32,33,38,39 SIFSIX-3-Fe, [Fe(pyz) 2 (SiF 6 )] (Fig. 1), is synthesized, and its sorption behavior is compared with its Ni analogue, SIFSIX-3-Ni.…”

Fluorine-functionalized metal–organic frameworks and porous coordination polymers

“…The SiF 6 2 − pillars had an important role in the formation of favorable MOFsorbate interactions via non-coordinated F atoms, which was confirmed using modeling studies, and X-ray and neutron diffraction analysis. 21,23,26 The exceptional CO 2 …”

“…AF 6 2 − anions (A = Si, Ge, Sn and Ti) can be used as bridging ligands for MOFs due to their high density of negative charge on fluorine atoms. [18][19][20][21][22][23][24][25][26][27]29,50 There are many AF 6 2 − -bridged MOFs, Fluorine-functionalized MOFs/PCPs S Noro and T Nakamura primitive cubic structure constructed from two-dimensional [M(4,4′-bpy) 2 ] n sheets and inorganic SiF 6 2 − pillars. 18,19 The Cu(II) compound, [Cu(SiF 6 )(4,4′-bpy) 2 ] (SIFSIX-1-Cu), was shown to have permanent pores and exhibit a high uptake of CH 4 (6.5 mmol g − 1 at 298 K and 36 atm) and selective CO 2 uptake over CH 4 (10.5 (IAST CO 2 /CH 4 (50:50) selectivity) at 298 K and 1 atm), and selective C 2 H 2 uptake over C 2 H 4 (8.37 (IAST C 2 H 2 /C 2 H 4 (50:50) selectivity) at 298 K and 1 atm).…”