Direct Observation and Quantification of CO 2 Binding Within an Amine-Functionalized Nanoporous Solid

• Published in: Science (American Association for the Advancement of Science) 2010-10, Vol.330 (6004), p.650-653
• Main Authors: Vaidhyanathan, Ramanathan, Iremonger, Simon S., Shimizu, George K. H., Boyd, Peter G., Alavi, Saman, Woo, Tom K.
• Format: Article
• Language: English
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1194237

One widely discussed means of stemming the rise in atmospheric carbon dioxide concentration is to capture the gas prior to its emission and then bury it. The materials currently known to best adsorb CO 2 for this purpose tend to involve amine groups; however, the precise molecular details of adsorption often remain murky, and rational improvement of sorbent properties by structural modification has been challenging. Vaidhyanathan et al. (p. 650 ; see the Perspective by Lastoskie ) have crystallographically resolved the binding motifs of CO 2 in an amine-bearing metal-organic framework solid. Accompanying theoretical simulations matched the experimental observations. Crystallographic resolution of bound carbon dioxide in a porous solid validates methods of theoretically predicting binding behavior. Understanding the molecular details of CO 2 -sorbent interactions is critical for the design of better carbon-capture systems. Here we report crystallographic resolution of CO 2 molecules and their binding domains in a metal-organic framework functionalized with amine groups. Accompanying computational studies that modeled the gas sorption isotherms, high heat of adsorption, and CO 2 lattice positions showed high agreement on all three fronts. The modeling apportioned specific binding interactions for each CO 2 molecule, including substantial cooperative binding effects among the guest molecules. The validation of the capacity of such simulations to accurately model molecular-scale binding bodes well for the theory-aided development of amine-based CO 2 sorbents. The analysis shows that the combination of appropriate pore size, strongly interacting amine functional groups, and the cooperative binding of CO 2 guest molecules is responsible for the low-pressure binding and large uptake of CO 2 in this sorbent material.