Herein, we have developed a new 7-diethylamino-4-hydroxycoumarin appended acylhydrazone (L) probe using a simple condensation reaction. The structure of the probe L was characterized via single crystal X-ray analysis. This probe L can selectively detect Al³⁺ metal ions via a colorimetric as well as fluorescence turn-on strategy over other metal ions. Besides, the probe can also detect the aluminium ions in pharmaceutical tablets. The resulting L-Al³⁺ ensemble has been exploited as a turn-off fluorescence sensor for the detection of pyrophosphate (PPi) anion through metal displacement or by using a decomplexation approach. Based on reversible “off–on–off” emission characteristics, the probe was applied for the construction of molecular logic gates and the development of a paper strip kit for on-site detection applications. In addition, this ensemble can also be utilized to detect PPi released during DNA synthesis and biological extracts, and in live cells.