Fig. 2

IR spectra of a SBPy-Zn(x,0) with x = 0–30% and b SBPy-Zn(20,y) with y = 0–4. The absorbance was normalized to the value of the 2950 cm−1 peak (saturated C–H stretching vibration) as an internal reference and was vertically shifted for clarity. The dashed lines indicate the position of the C‒N stretching vibration peak attributed to noncoordinated and coordinated pyridine groups