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 (ΔHads) 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 ΔHads 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 ΔHads 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.