Nitrogen Interaction with Various 1D and 3D Nanostructured Carbon Architectures Probed VIA in-SITU Vibrational Spectroscopy

The study utilizes in-situ vibrational spectroscopy to probe nitrogen adsorption to porous carbon materials. Combined theoretical and experimental studies demonstrate how the nitrogen vibrational spectra becomes perturbed by a carbon surface as well as nearest neighbor gas molecules. The perturbation is sensitive to gas-surface binding energy, pore structure, and surface chemistry. As the pore dimension of a Polymer of Intrinsic Microporosity (PIM-1) is reduced via photochemical irradiation, the position and intensity of the perturbation tracks the pore dimension. Chemical alteration of the PIM-1 surface, along with control studies with nonporous analogs, elucidates the role of surface chemistry, demonstrating π-π stacking interactions between the C-N group and the N-N triple bond. The nitrogen spectra is similarly perturbed in non-functionalized activated carbon and single-wall nanotubes of varying dimension. The relative intensity of the perturbed N₂ mode tracks the cryogenic volumetric adsorption isotherms; as the spectroscopic probe can be completed in a few hours for a few micrograms of sample, the spectroscopic method provides a rapid screening alternative. Moreover, the spectroscopic probe elucidates site-specific interactions, which may advance the understanding of adsorbent geometry and chemical functionality, beyond that possible from deconstruction of bulk gas adsorption isotherms.