MOF Effectively Captures CO2 Even from Dilute Air Streams

By Muhammad OsamaReviewed by Frances BriggsMar 10 2026

A new study shows that grafting ethylenediamine onto the pyrazole-based MOF-303 framework creates high-affinity CO₂-binding sites, improving capture from ultra-dilute streams and diluted point sources while allowing regeneration in relatively mild conditions.

Study: Diamine Grafting of Pyrazole-Based MOF-303 for Diluted-Source CO₂ Capture. Image Credit: Lupae/Shutterstock.com

Carbon dioxide emissions from fossil fuel use remain a major driver of climate change, with atmospheric CO₂ levels now around 420 ppm, up from roughly 280 ppm before industrialization. Reporting in Small, researchers have described a new way to improve carbon capture using a metal-organic framework, or MOF, engineered to bind CO₂ strongly even at very low concentrations.

The team modified MOF-303 with ethylenediamine (EDA) to produce MOF-303#EDA, a material that showed stronger CO₂ uptake under ambient-air-like conditions and in diluted point-source gas streams.

The study combines adsorption measurements, spectroscopy, solid-state NMR, and modelling to show how the grafted diamine changes the pore chemistry and adsorption behaviour of the framework.

MOFs for Low-Concentration CO₂ Capture

MOFs are crystalline, porous materials formed by linking metal ions to organic ligands. Their structural tunability has made them particularly appealing for studies in gas storage and separation, including CO₂ capture.

That has drawn interest for low-concentration separations such as direct air capture, where conventional aqueous amine systems can be energy-intensive to regenerate. Solid sorbents such as MOFs are being explored as alternatives because they can combine selectivity with lower regeneration demands.

In this case, the researchers focused on MOF-303 and then introduced diamine functionality through the chemistry of its pyrazole-containing framework.

Saving this for later? Grab a PDF here.

Solvent-Free Grafting Inside The Framework

Pristine MOF-303 was synthesized hydrothermally, activated under high vacuum, and then exposed to EDA vapour in a solvent-free diffusion process for three days. Grafting proceeds via deprotonation of pyrazole sites within the framework.

The authors describe this as more than a simple addition of amines to pore surfaces. The pyrazole-based environment enables acid-base interactions and charge-assisted hydrogen bonding, anchoring EDA within the pores and generating well-defined CO₂ adsorption sites.

MOF-303#EDA was then characterized using thermogravimetric analysis, nitrogen adsorption-desorption isotherms, infrared spectroscopy, and solid-state nuclear magnetic resonance, all of which supported successful EDA incorporation.

Pore Changes And Adsorption Sites

Pristine MOF-303 had a specific surface area of 1469 m²/g. After EDA grafting, that fell to around 50 m²/g. Rather than indicating only a loss of porosity, the change is consistent with EDA occupying pore space and establishing more specific binding environments for CO₂.

Density functional theory calculations were used to probe that structural change. The modelling indicated strong interactions between EDA and the framework and suggested that grafting introduces constrictions within the channels, which help explain the pronounced low-pressure uptake observed experimentally.

Uptake From Ultra-Dilute and Dilute Streams

MOF-303#EDA showed CO₂ uptakes of 0.71 mmol/g at 450 ppm and 1.03 mmol/g at 1000 ppm, pointing to strong performance under ultra-dilute conditions. Its adsorption isotherm rose steeply at low pressures, consistent with high-affinity binding sites in the modified framework.

At higher partial pressure, the material reached a CO₂ uptake of 2.58 mmol/g at 0.15 bar and 298 K. The study, therefore, places the material in the context of both ambient-air-like capture and diluted industrial gas streams, rather than DAC alone.

Chemisorption With Moderate Regeneration Conditions

The isosteric heat of adsorption was measured at 55 kJ/mol, a value consistent with chemisorption. The authors report that regeneration nevertheless remains feasible under relatively mild conditions, with desorption occurring at around 68°C.

Infrared spectroscopy and solid-state NMR point to the formation of carbamate and carbamic acid species during CO₂ adsorption. Those observations help account for the strong binding behaviour and clarify the chemistry responsible for the material’s low-pressure performance.

Breakthrough Cycling Under CO₂/N₂ Mixtures

The study also includes breakthrough testing under a 5:95 CO₂/N₂ stream, during which MOF-303#EDA completed 10 consecutive cycles without loss of performance. That provides direct support for diluted point-source capture under repeated operation.

The authors also note that MOF-303 is assembled from relatively inexpensive, scalable building blocks, which adds a practical dimension to the materials design strategy described in the paper.

The results show that grafting EDA onto a pyrazole-based MOF yields a sorbent that combines strong low-pressure CO₂ uptake, spectroscopic evidence of chemisorption, repeated breakthrough stability, and regeneration at comparatively modest temperatures.

Future work will need to establish longer-term behaviour under more complex operating conditions, but the study offers a detailed example of how linker chemistry can be used to shape adsorption sites in porous solids for diluted-source CO₂ capture.

Journal Reference

Mastronardi, G., et al. (2026). Diamine Grafting of Pyrazole-Based MOF-303 for Diluted-Source CO2 Capture. Small. e14197. DOI: 10.1002/smll.202514197

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.