© 2022 Elsevier B.V.The aim of this work is to construct a new A2B2-type of unsymmetrical and ratiometric phthalocyanine (Pc) based-probe O-A2B2ZnPc to provide an effective solution to critical inadequacy to be experienced for the detection of hazardous Be2+. O-A2B2ZnPc enabling strong absorption and emission in Near-Infrared region (λabs-λem wavelengths of 694–712 nm) showed excellent selectivity and sensitivity toward Be2+ among competitive metal ions by both spectrophotometric and fluorometric methods. The probe with oligomeric Pc form in THF was degraded with the addition of aqueous Be2+ and arranged to J-aggregation form, resulting in a remarkably diminishing in Q-band at 694 nm as well as a new band formation at 746 nm, and a considerably decreasing in fluorescence emission. The probe has superior features for the determination of Be2+ such as high quantum efficiency and photochemical stability, rapid response (1 s), high selectivity and very low Limit of Detection (0.26 ppb and 1.5 ppb) for UV–Vis and fluorescence, respectively which are quite good values according to the permissible amount of Be2+ (4 ppb) in water as specified by World Health Organization. O-A2B2ZnPc can be shown among the best performing probes with its unique properties according to previous studies in the literature. In addition, the geometrical and spectral features of the O-A2B2ZnPc were analyzed in detail by DFT calculations.