“…The World Health Organization (WHO) has claimed a permissible limit of 50 μg/L for Cr(VI) in drinking water [ 20 ]. Lately, MOF/CP-based, fluorescence-sensory materials have been actively pursued as excellent platforms for the flourishing utilization in detection of Cr(III) and Cr(VI) ions though fluorescence quenching (turn off) effect [ 15 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. However, there are still rare examples to achieve the detection of Cr(III) via the fluorescence enhancement (turn on) response [ 15 , 43 , 44 , 45 , 46 , 47 , 48 ] and fluorescence shift (ratiometric) effect [ 41 , 42 , 43 ].…”