Great Location: About Effects of Surface Bound Neighboring Groups for Passive and Active Fine-Tuning of CO₂ Adsorption Properties in Model Carbon Capture Materials.

Abstract

Improved carbon capture materials are crucial for managing the CO₂ level in the atmosphere. The past focus was on increasing adsorption capacities. It is widely known that controlling the heat of adsorption (ΔH_ads ) is equally important. If it is too low, CO₂ uptake takes place at unfavorable conditions and with insufficient selectivity. If it is too high, chemisorption occurs, and the materials can hardly be regenerated. The conventional approach for influencing ΔH_ads is the modification of the adsorbing center. This paper proposes an alternative strategy. The hypothesis is that fine-tuning of the molecular environment around the adsorbing center is a powerful tool for the adjustment of CO₂ -binding properties. Via click chemistry, any desired neighboring group (NG) can be incorporated on the surfaces of the nanoporous organosilica model materials. Passive NGs induce a change in the polarity of the surface, whereas active NGs are capable of direct interaction with the active center/CO₂ pair. The effects on ΔH_ads and on the selectivity are studied. A situation can be realized which resembles frustrated Lewis acid-base pairs, and the investigation of the binding-species by solid-state NMR indicates that the push-pull effects could play an essential role not only in CO₂ adsorption but also in its activation.