A novel fluorescent sensor, 4′-hydroxy-3′-(((2-hydroxyphenyl)imino)methyl)-4-biphenylcarbonitrile (AAF) was synthesized and characterized by combination of 1H, 13C, APT, COSY NMR, FT-IR, and elemental analysis. The behaviors of the receptor AAF toward different metal ions were determined by UV-vis and fluorescence spectroscopy. The receptor AAF exhibited a 24-fold increase in fluorescence intensity in the presence of Al3+ over most other competitive metal ions in CH3CN-water (v/v, 1/1).