UV and chemical modifications of polymer of Intrinsic Microporosity 1 to develop vibrational spectroscopic probes of surface chemistry and porosity

This work probes host-guest interactions of nitrogen using in-situ vibrational spectroscopy, as the pore structure, pore size, and surface chemistry of a Polymer of Intrinsic Microporosity (PIM-1) are varied. N2 adsorption to PIM-1 renders the N2 infrared vibron active, establishing a weak dipole-dipole interaction. The perturbation of the N2 vibrational mode at room temperature is much stronger for PIM-1 than other porous carbon materials, implicating the C-N surface group of PIM-1 in the degree of shift in the vibrational spectra and suggesting a strong π-π stacking gas-surface interaction. No perturbation of the N2 spectra is observed for a non-porous C-N analogue (tetrafluoro-terepthalonitrile) or after conversion of the C-N group of PIM-1 to an amide. The pore size of PIM-1 is reduced via UV irradiation, leading to an increase in the shift of the Raman-active N2 perturbation.