Cu2+-based metal-organic framework (Cu-TCA) (H3TCA = tricarboxytriphenyl amine) having triphenylamine emitters was assembled and structurally characterized. Cu-TCA features a three-dimensional porous structure consolidated by the well-established Cu2(O2CR)4 paddlewheel units with volume of the cavities approximately 4000 nm3. Having paramagnetic Cu2+ ions to quench the luminescence of triphenylamine, Cu-TCA only exhibited very weak emission at 430 nm; upon the addition of NO up to 0.1 mM, the luminescence was recovered directly and provided about 700-fold fluorescent enhancement. The luminescence detection exhibited high selectivity other reactive species present in biological systems, including H2O2, NO3-, NO2-, ONOO-, ClO- and 1O2, did not interfere with the NO detection. The brightness of the emission of Cu-TCA also led to its successful application in the biological imaging of NO in living cells. As a comparison, lanthanide metal-organic framework Eu-TCA having triphenylamine emitters and characteristic europium emitters was also assembled. Eu-TCA exhibited ratiometric fluorescent responses towards NO with the europium luminescence maintained as the internal standard and the triphenylamine emission exhibited more than 1000-fold enhancement.