Made-to-order metal-organic frameworks for trace carbon dioxide removal and air capture

Abstract

Direct air capture is regarded as a plausible alternate approach that, if economically practical, can mitigate the increasing carbon dioxide emissions associated with two of the main carbon polluting sources, namely stationary power plants and transportation. Here we show that metal-organic framework crystal chemistry permits the construction of an isostructural metal-organic framework (SIFSIX-3-Cu) based on pyrazine/copper(II) two-dimensional periodic 44 square grids pillared by silicon hexafluoride anions and thus allows further contraction of the pore system to 3.5 versus 3.84 Å for the parent zinc(II) derivative. This enhances the adsorption energetics and subsequently displays carbon dioxide uptake and selectivity at very low partial pressures relevant to air capture and trace carbon dioxide removal. The resultant SIFSIX-3-Cu exhibits uniformly distributed adsorption energetics and offers enhanced carbon dioxide physical adsorption properties, uptake and selectivity in highly diluted gas streams, a performance, to the best of our knowledge, unachievable with other classes of porous materials.

Low concentration CO2 capture using physical adsorbents: Are metal–organic frameworks becoming the new benchmark materials?

“…In line with this, a new class of MOFs with periodically arrayed hexafluorosilicate (SiF 6 ) pillars 10,94 ( Figure 7) characterized by one-dimensional channels with different sizes and exhibiting uniform and strong energy distribution with increased CO 2 uptake (grey, blue, and black dots, Figure 3b) These SiF 6 based MOFs, particularly the isostructural analogues constructed using (the shorter) pyrazine ligand (Figure 7), showed unprecedented selectivity for CO 2 . Uniform CO 2 interaction (energy) distribution is one of the essential requirements to ensure (in addition to narrow pore size) that high selectivity is maintained over a wide range of CO 2 adsorption loading.…”

“…Uniform CO 2 interaction (energy) distribution is one of the essential requirements to ensure (in addition to narrow pore size) that high selectivity is maintained over a wide range of CO 2 adsorption loading. 10,94 This key aspect has not been tackled and discussed in the literature so far, which explains the scarcity of materials that are able to fulfill the technical requirements for CO 2 capture. 96 It is important to mention that the higher is the CO 2 concentration in the stream, the steadier should be the adsorption energy (heat of adsorption).…”

Synthesis and Crystal Structure of a Zn(II)-Based MOF Bearing Neutral N-Donor Linker and SiF62− Anion

“…In pioneering reports, Zaworotko and Kitagawa have reported MOFs utilizing SiF 6 2− as counter anion and neutral nitrogen donor linker [17,18]. Recently, (SiF 6 2− ) anion has been utilized extensively due to the tendency of SiF 6 2− to bridge two-dimensional sheets to form an overall three-dimensional framework with formation of one dimensional channel with varied porosity depending on the length of the linker [19,20]. Owing to the presence of highly electronegative fluorine atoms in SiF 6 2− it leads to the formation of highly charged polar surfaces.…”

Flue gas adsorption by single-wall carbon nanotubes: A Monte Carlo study

“…[9][10][11] As necessary starting steps in reversible capture and storage technologies and carbon reutilization, adsorption and membrane separation of CO 2 from flue gases have been deeply researched. 12 Many possible materials have been considered for CO 2 adsorption, including zeolites, 13,14 activated carbon, 15,16 metal-organic frameworks, 17,18 and single-wall carbon nanotubes (SWCNTs). 19 The latter have been identified as vessels for short-term reversible storage of CO 2 at ambient temperatures.…”