Spatial tuning of adsorption enthalpies by exploiting spectator group effects in organosilica carbon capture materials

authored by: Mario Evers, Karin Hauser, Wolfgang G. Hinze, Nele Klinkenberg, Yasar Krysiak, Daniel Mombers, Sebastian Polarz
Abstract: Functional gradient materials can process more complex tasks than a mixture of their homogeneous analogs. Generating such materials is difficult as it necessitates spatial control over chemical and/or structural properties. A gradient is a unique degree of freedom in hierarchical material architectures, and as such, biology has managed exploiting the full potential of graded structures. For instance, despite being present at a comparably low concentration (approaching 420 ppm in 2023), plants are capable of capturing carbon dioxide from the air. Binding occurs in the carboxysome, a complex entity characterized by pores with engineered surfaces composed of shell proteins that create a concentration gradient of CO₂ towards an enzyme responsible for the first conversion step. The current paper hypothesizes that porous organosilica materials can mimic some of the features of the mentioned biological paragon. Primary amines as sites for interacting with CO₂ are surrounded by spectator groups on bifunctional surfaces. It is found that the proper choice of the spectator group almost doubles the adsorption enthalpy. Above a critical density, the hydrophobic moieties create a quasi-solvent layer on the surfaces in which CO₂ molecules dissolve. When the density of the spectator groups gradually changes inside a graded organosilica monolith, one obtains zones varying systematically in adsorption enthalpy. Directionality in affinity towards CO₂ and controlled transport properties are realized.
Organisation(s): Institute of Inorganic Chemistry
External Organisation(s): University of Konstanz
Type: Article
Journal: Journal of Materials Chemistry A
No. of pages: 12
ISSN: 2050-7488
Publication date: 04.04.2024
Publication status: E-pub ahead of print
Peer reviewed: Yes
ASJC Scopus subject areas: Chemistry(all), Renewable Energy, Sustainability and the Environment, Materials Science(all)
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy
Electronic version(s): https://doi.org/10.1039/d4ta01381f (Access: Open)