Metal-organic framework (MOF) layers were grown in situ from 2D transition metal carbides (MXenes, Ti₃C₂T_x) at room temperature to obtain the two-dimensional (2D) Ti₃C₂T_x@MOF heterostructures with a tightly connected interface. This interface provided more titanium atoms in the low-valence state in comparison to the original Ti₃C₂T_x, thus facilitating more electron transfer from Ti₃C₂T_x to MOF-(Fe/Co) nanosheets. The charge density difference and density functional theory results disclosed that Ti₃C₂T_x could modulate the electronic density around the active sites and lower ΔG_H* energy barrier of 2D MOF-(Fe/Co) nanosheets towards the improved hydrogen evolution reaction (HER) activity. The obtained 2D Ti₃C₂T_x@MOF heterostructures exhibited a much higher HER activity in 1 M KOH electrolyte (with the overpotential of 104 mV at 10 mA/cm² and Tafel slope of 79 mV/dec) than those of 2D Ti₃C₂T_x@MOF-TH, 2D MOF nanosheets, and Ti₃C₂T_x nanosheets. This research provides a basis for developing superior 2D MOFs, which can enhance HER properties through efficient electronic transport at the heterojunction interface.