A　copper(II)-based　two-dimensional　metal-organic　framework　with　nanosheet　structure　(CuBDC　NS)　that　possesses　peroxidase　(POx)　mimicking　activity　was　prepared.　In　the　presence　of　hydrogen　peroxide,　the　system　catalyses　the　oxidation　of　terephthalic　acid　to　a　blue-fluorescent　product　(excitation　=　315 nm;　emission　=　425 nm).　Pyrophosphate　has　a　very　strong　affinity　for　Cu　2+　ion and　blocks　the　POx-mimicking　activity　of　the CuBDC　NS.　If,　however,　inorganic　pyrophosphatase　is　present,　the　POx　mimicking　activity　is　gradually　restored　because　pyrophosphate　is　hydrolyzed.　The　findings　were　used　to　design　a　method　for　the　determination　of　the　activity　of　inorganic　pyrophosphatase by　fluorometry.　Fluorescence　increases　linearly　in　the　1–50 mU·mL　−1　 inorganic　pyrophosphatase　activity　range.　The　limit　of　detection　is　0.6 mU·mL　−1　(S/N =　3).　[Figure　not　available:　see　fulltext.].　©　2019,　Springer-Verlag　GmbH　Austria,　part　of　Springer　Nature.