Fig. 1. Characterization of IF-PTI and PTI·H₂O materials.

(A) Powder XRD patterns for IF-PTI and PTI·H₂O. a.u., arbitrary units. (B) TEM image of hexagonal crystallites of IF-PTI showing lattice planes. (C) Fourier-transformed pattern showing characteristic diffraction spots of [110] (inner ring of spots in a hexagonal pattern) and [100] in-plane reflections of the PTI layers corresponding to real-space interatomic separations of 4.25 and 7.35 Å, respectively. (D) Thermogravimetric analysis (TGA) data for PTI·H₂O between 300 and 1200 K. The initial reduction in mass of ~9% between 300 and 500 K is due to deintercalation of one H₂O molecule per C₆N₉H₃ formula unit of the layered PTI structure (19). The larger mass loss observed above 800 K is due to thermal decomposition of the IF-PTI carbon nitride phase. (E) Variation in elastic neutron scattering intensity observed during heating PTI·H₂O between 200 and 530 K. (F and G) Top and side views of the C₁₂N₁₂H₃ intralayer pores showing the equilibrium location of H₂O molecules determined by DFT calculations.