Boric acid is a crystalline solid that contains an interconnected network of hydrogen bonds. The 1 wt% TPA-CO2H films in boric acid were fabricated by drop-casting methanol solutions onto glass substrates. A putative host-guest hydrogen-bonded network is shown in Figure . Under 365 nm excitation, blue luminescence was observed, followed by a blue afterglow lasting over 1 s upon ceasing the excitation (Figure , top), a behavior similar to that observed for the doped films in PVA. The steady-state PL measurements are likewise similar to those measured in PVA (Figures and), with lPL of 433 nm and tPL of 1.1 ns (Figure ). Time-gated phosphorescence spectra recorded at 298 and 77 K show that the emission stems from a monomeric species as the phosphorescence emission profile is almost identical to that obtained in dilute 2-MeTHF glass at 77 K (Figures 3d). for the RTP is 101 ms (Figure ) and the recorded FPh is 3%, which is much lower than that recorded in PVA (FPh = 46%). The PXRD patterns of the drop-cast TPA-CO2H/boric acid composite shows an identical pattern to that of boric acid at 1 and 3 wt% doping, reflecting that the amount of TPA-CO2H falls below the detection limit of the PXRD experiment (Figure ). The 5 and 10 wt% doped films show additional peaks in the PXRD, associated both with the presence of regions of TPA-CO2H and a new composition. The observed afterglow is significantly attenuated at these doping concentrations, ascribed to ACQ (Figure ).