Selective gas capture via kinetic trapping

TL;DR

This paper proposes a novel non-equilibrium method for selective CO2 capture using metal-organic frameworks, leveraging differences in gas mobility rather than equilibrium affinity.

Contribution

It introduces a statistical mechanical model showing how kinetic trapping enables selective gas separation in frameworks previously considered unsuitable.

Findings

Kinetic trapping enhances CO2 separation efficiency.

Heterogeneous gas distribution within frameworks aids selectivity.

Non-equilibrium conditions expand material applicability.

Abstract

Conventional approaches to the capture of CO_2 by metal-organic frameworks focus on equilibrium conditions, and frameworks that contain little CO_2 in equilibrium are often rejected as carbon-capture materials. Here we use a statistical mechanical model, parameterized by quantum mechanical data, to suggest that metal-organic frameworks can be used to separate CO_2 from a typical flue gas mixture when used under {\em nonequilibrium} conditions. The origin of this selectivity is an emergent gas-separation mechanism that results from the acquisition by different gas types of different mobilities within a crowded framework. The resulting distribution of gas types within the framework is in general spatially and dynamically heterogeneous. Our results suggest that relaxing the requirement of equilibrium can substantially increase the parameter space of conditions and materials for which selective gas capture can be effected.