A steam-stable MOF for high-capacity carbon capture

A recently discovered family of highly porous metal-organic framework (MOF) materials is showing promise in carbon-capture applications. Researchers from University of California, Berkeley (www.berkeley.edu), Lawrence Berkeley National Laboratory (LBL; www.lbl.gov) and ExxonMobil Corp. (Irving, Tex.; www.exxonmobil.com) demonstrated the efficacy of the new tetra-amine-functionalized magnesium-based MOFs in removing CO₂ emissions — reporting a six-fold increase in effectiveness over conventional amine-based carbon-capture methods.

“This family of MOF materials has a very high density of metals in the three-dimensional porous framework, and these metals have open coordination sites. This high density means we can incorporate a large number of amine groups bound to these open metal sites in an ordered fashion, which in turn leads to the potential for a high capture capacity for CO₂,” explains Simon Weston, senior research associate and the project lead at ExxonMobil Research and Engineering Co. He adds that while earlier research looked at incorporating diamine groups into the MOF, which only provided one attachment point for CO₂, switching to tetra-amines provided additional attachment points and also served to improve the material’s thermal stability during steam cycling. This stability enables regeneration (and therefore, repeated re-use) of the material using steam at relatively low temperatures (110–120°C), which decreases overall energy consumption when compared to other carbon-capture methods.

The team’s work has demonstrated that the MOFs are highly selective for CO₂ and could capture over 90% of the CO₂ emitted from industrial sources. The combination of this high CO₂-capture capacity alongside thermal stability and ease of regeneration using low-temperature steam make this material an attractive prospect for industrial carbon capture. However, notes Weston, the technology has thus far only been demonstrated at laboratory scale, and additional work will be required to progress the technology to a larger-scale pilot.