A　smartphone-assisted　electrochemiluminescence　(ECL)　strategy　based　on　Ru(bpy)2(L)4+　as　chromophores　confined　with　metal　−　organic　frameworks　(Ru(bpy)2(L)4+@MOF-5)　for　the　signal-amplified　detection　of　miRNA-21　was　developed.　We　synthesized　a　derivative　of　tris(2,2’-bipyridyl)ruthenium(II)　complex　(Ru(bpy)2(L)4+)　with　high　charges,　which　can　be　loaded　into　the　MOF-5　by　strong　electrostatic　interaction　to　prevent　from　leakage.　In　addition,　nucleic　acid　cycle　amplification　was　used　to　quench　the　signal　of　Ru(bpy)2(L)4+@MOF-5　by　ferrocene.　This　method　was　applied　to　detect　the　concentration　of　miRNA-21　ranging　from　1.0　×　10−14-1.0　×　10−9　M　with　a　low　LOD　of　7.2　fM.　This　work　demonstrated　the　construction　of　a　signal　quenching　strategy　ECL　biosensor　for　miRNA　using　Ru(bpy)2(L)4+@MOF-5　systems　and　its　application　in　smartphone-assisted　ECL　detection.　Graphical　abstract:　(Figure　presented.)　©　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH　Austria,　part　of　Springer　Nature　2024.