Nitrogen-containing mesoporous carbons via nanocasting for CO2 capture and energy storage applications

In this work, nitrogen-containing ordered mesoporous carbons (NOMCs) are proposed as CO2 adsorbents. The nanocasting approach, using ordered mesoporous silica hard templates, was exploited for tuning the textural features of the carbonaceous adsorbents and therefore optimizing their capture performances and the kinetics of gas diffusion. Moreover, an eco-friendly nitrogen-containing carbon source was chosen as a precursor, in order to introduce basic sites useful to promote the interaction with the acidic CO2 molecule, thus fostering a selective adsorption in a gas mixture. CMK-8 materials were prepared using KIT-6 templates, varying the pyrolysis temperature in order to evaluate the role of microporosity and nitrogen species (amount and type of N inclusions, i.e. pyridinic, pyrrolic and graphitic) in CO2 adsorption. An extensive characterization of the ordered mesoporous architecture (low-angle XRD, FESEM, TEM and N2 physisorption at 77K), microporosity (CO2 isotherms at 273K) and surface chemical properties by XPS was carried out. CO2 capture tests were performed in different conditions of temperature and pressure. An adsorption of 1.05 mmol/g (4.6% weight increase) was achieved at 30 °C and 90 kPa in a pure CO2 flow. Also selectivity in a mixture with N2 and reusability upon cycling was investigated. The described NOMCs can be applied not only for CO2 up-take, but also in energy storage and conversion devices (e.g., lithium or sodium based batteries), photocatalysis or electrocatalytic reduction of CO2. For these applications, they can be used as-synthesized or decorated with specifically selected metal oxides and testing is now in progress in our laboratories.