Flue-gas and direct-air capture of CO ₂ by porous metal–organic materials

Abstract

Sequestration of CO, either from gas mixtures or directly from air (direct air capture), is a technological goal important to large-scale industrial processes such as gas purification and the mitigation of carbon emissions. Previously, we investigated five porous materials, three porous metal-organic materials (MOMs), a benchmark inorganic material, ZEOLITE 13X: and a chemisorbent, TEPA-SBA-15: , for their ability to adsorb CO directly from air and from simulated flue-gas. In this contribution, a further 10 physisorbent materials that exhibit strong interactions with CO have been evaluated by temperature-programmed desorption for their potential utility in carbon capture applications: four hybrid ultramicroporous materials, SIFSIX-3-CU: , DICRO-3-NI-I: , SIFSIX-2-CU-I: and MOOFOUR-1-NI: ; five microporous MOMs, DMOF-1: , ZIF-8: , MIL-101: , UIO-66: and UIO-66-NH2: ; an ultramicroporous MOM, NI-4-PYC: The performance of these MOMs was found to be negatively impacted by moisture. Overall, we demonstrate that the incorporation of strong electrostatics from inorganic moieties combined with ultramicropores offers improved CO capture performance from even moist gas mixtures but not enough to compete with chemisorbents.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

A highly stable metal‐organic framework with optimum aperture size for CO2 capture

“…Samples were treated via Pt sputtering before observations. The apparent skeletal densities of MOF samples [1.29 g mL 21 and 1.015 g mL 21 for HKUST-1 and opt-UiO-66(Zr)-(OH) 2 , respectively] were measured by a mercury porosimeter (Micromeritics Autopore III 9420). The bed porosities of columns filled with MOFs were calculated to be 0.595 for the 14 cm column packed with HKUST-1, and 0.485 for the 14 cm and 0.61 for the 8 cm column packed with opt-UiO-66(Zr)-(OH) 2 .…”

“…Considering the ultrasmall aperture size and enhanced pore wall polarity brought by the dangling hydroxyl groups, which have been proven to be highly favorable for CO 2 adsorption, 25,26 the low-pressure gas sorption properties of opt-UiO-66(Zr)-(OH) 2 were studied by conducting gas sorption tests at 273 K and 298 K, respectively, with pressures up to 1 bar (Figure 2c and Supporting Information Figure S4). Opt-UiO-66(Zr)-(OH) 2 demonstrates a high CO 2 working capacity [defined as the CO 2 uptake capacity difference between adsorption at $0.15 bar (partial pressure of CO 2 in flue gas) and desorption at $0 bar] of 2.50 mmol g 21 , which is 575 and 38% higher than that of UiO-66(Zr) (0.37 mmol g 21 ) and UiO-66(Hf)-(OH) 2 (1.81 mmol g 21 ), respectively. 36 To the best of our knowledge, this is the highest CO 2 working capacity obtained among all the reported water-stable MOFs without extra modification (e.g., PSMs, amine doping).…”

“…For example, Zaworotko and coworkers reported a series of SIFSIX-based MOFs with ultra-small pore size (as low as 3 Å ) and hydrophobic interiors for postcombustion CO 2 capture, 25 direct air CO 2 capture, 26,27 and hydrocarbon separations. 28,29 Vaidhyanathan and coworkers exquisitely designed a MOF, Ni-(4-pyridylcarboxylate) 2 , with an aperture size of 3.5-4.8 Å , which exhibits high CO 2 /H 2 separation performance for precombustion CO 2 capture. 30 The underlying design principle of the above approach is that MOFs with ultrasmall pore sizes are endowed with strong van der Waals interactions with adsorbed gas molecules.…”

Rapid CO2 capture from ambient air by sorbent‐containing porous electrospun fibers made with the solvothermal polymer additive removal technique

“…Direct air capture (DAC), the process of removing carbon dioxide directly from ambient air, has the potential to become a powerful tool for combating climate change . Sorbents are currently being studied to accomplish this task including metal–organic frameworks (MOFs), activated carbons, zeolites, ion‐exchange resins (IERs), and amine‐tethered materials . Important characteristics of a sorbent for DAC include high uptake capacities, fast uptake rates, and an economically viable regeneration process .…”

Coordination polymers and metal–organic frameworks: materials by design

“…Zaworotko and co-workers [11] report an extensive study of the adsorption of CO 2 by a range of MOFs, drawing comparisons between new MOFs and literature examples. Importantly, the authors conclude that those materials that are constructed using inorganic building blocks, such as (SiF 6 ) 2− anions, demonstrate improved CO 2 adsorption properties in comparison with other MOF systems.…”