CO2 and SF6 adsorption on mixed-linker ZIF-7-8s: The effect of linker substitution on gas uptake and selectivity

• A series of mixed-linker Zeolitic Imidazolate Framework(ZIF)-7–8s constructed from varying amounts of benzimidazolate (bIm) and 2-methylimidazolate (mIm) linkers are reported in this study. We demonstrate that the particle morphology and pore size of ZIF-7–8 can be tailored by carefully adjusting the ratios between bIm and mIm linkers in the frameworks resulting in a significantly enhanced CO2 or SF6 uptake capacity and selectivity. ZIF-7–8 containing 90% bIm and 10% mIm linkers were shown to have a CO2 uptake capacity of 1.44 mmol g−1 at 293 K (1 bar) and a CO2/N2 selectivity of over 30. While ZIF-7–8 with 26% bIm and 74% mIm linkers had a SF6 uptake of 2.08 mmol g−1 at 293 K (1 bar) and a high SF6/N2 selectivity of over 40. Isosteric enthalpy of adsorption calculations and cyclic pressure-swing adsorption experiments showed that both CO2 and SF6 were physisorbed on ZIF-7–8. The adsorption of CO2 was also found to occur rapidly on all samples, with over 80% of the total uptake capacity being reached within 30 s. Detailed kinetics analysis concluded that the diffusion of CO2 and SF6 in the mixed-linker ZIF-7–8s were governed by a mixture of different mechanisms, including intracrystalline diffusion. The highly tunable sorption properties, uptake capacities and high gas selectivities of ZIF-7–8 render them as interesting candidate sorbents for certain greenhouse gases.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Nanoteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Nano-technology (hsv//eng)

Nyckelord

Metal-organic frameworks

MOFs

Zeolitic imidazolate frameworks

ZIFs

Carbon capture

Gas separation

Engineering Science with specialization in Nanotechnology and Functional Materials

Teknisk fysik med inriktning mot nanoteknologi och funktionella material

Publikations- och innehållstyp

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