• Energy Research

The first sorbent with high CO 2 selectivity and poor water affinity addresses need for trace CO 2 remediation in confined spaces.

Sequestration of CO 2 , 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 2 directly from air and from simulated flue-gas. In this contribution, a further 10 physisorbent materials that exhibit strong interactions with CO 2 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-NH 2 ; 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 2 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’.

AbstractSequestration of CO2, either from gas mixtures or directly from air (direct air capture, DAC), could mitigate carbon emissions. Here five materials are investigated for their ability to adsorb CO2 directly from air and other gas mixtures. The sorbents studied are benchmark materials that encompass four types of porous material, one chemisorbent, TEPA‐SBA‐15 (amine‐modified mesoporous silica) and four physisorbents: Zeolite 13X (inorganic); HKUST‐1 and Mg‐MOF‐74/Mg‐dobdc (metal–organic frameworks, MOFs); SIFSIX‐3‐Ni, (hybrid ultramicroporous material). Temperature‐programmed desorption (TPD) experiments afforded information about the contents of each sorbent under equilibrium conditions and their ease of recycling. Accelerated stability tests addressed projected shelf‐life of the five sorbents. The four physisorbents were found to be capable of carbon capture from CO2‐rich gas mixtures, but competition and reaction with atmospheric moisture significantly reduced their DAC performance.

Fine-tuning of hybrid ultramicroporous materials (HUMs) can significantly impact their gas sorption performance.

In this report the photo-physical properties of 9-amino acridine (9AA) associated with αZr-phosphate particles (αZrP) is examined. In ethanol solution 9AA exhibits absorption maxima at 425 nm, 402 nm and 383 nm as well as emission bands centered at 455 nm and 483 nm (using 423 nm excitation). The corresponding emission decay is monophasic with a lifetime of 16.5 ns. When αZrP is sonicated in the presence of an ethanol solution of 1 mM 9AA the resulting material exhibits a broad absorption band centered at ∼400 nm with shoulders at ∼425 nm and ∼385 nm and emission bands at 462 nm and 485nm (using 423 nm excitation). Interestingly, the emission decay is biphasic with lifetimes of 1.6 ns and 9.8 ns constituting 57% and 43% of the total emission intensity, respectively. The absence of any shifts in the low angle XRD data suggests that 9AA associates via adsorption onto the exterior surfaces of the αZrP particles. Overall, these results are consistent with different modes of 9AA association to αZrP reflecting different degrees of H-bonding which significantly influences the extent of non-radiative decay from the lowest excited singlet state of 9AA.