An easy, in situ growth approach led to the formation of several composites of metal-organic framewoks and Nb4C3Tx MXenes mixed intimately at the submicron scale. The high affinity of MXene surface for dopamine, enhanced by a nanostructuration induced by MOFs, resulted in superior sensing performances. The system exhibited good linearity over the 1-100 nM range, with an excellent limit of detection of 0.2 nM.