In this work, we describe a facile construction of eco-friendly and effective nanocomposites from carbon dots (CDs), a novel type of carbon nanomaterial, for photocatalytic purposes. A series of benign CDs with favourable photoluminescence (PL) features were initially obtained from the hydrothermal treatment of natural vegetables including guava, red pepper, peas and spinach. The spinach-extracted CDs, with the highest PL emission intensity, were integrated with versatile TiO₂ ensembles, i.e. nanoparticles (NPs) and nanotubes (NTs), to form desirable nanocomposites by further hydrothermal synthesis. TEM images, coupled with XPS spectra, confirm that the CDs are well decorated on the surfaces of TiO₂. Due to the favourable electron transfer property of CDs, the H₂ generation rates are enhanced to 75.5 and 246.1 μmol g⁻¹ h⁻¹ for TiO₂ NP/CD and NT/CD nanocomposites, which are 21.6 and 3.3 times the rates of bare NPs and NTs, respectively. The strategy reported here may contribute to the fabrication of green and efficient nanocomposites for diverse applications.