Surface-functionalized nitrogen/carbon co-doped polymorphic TiO2 phase junction nanoparticles uniformly distributed in porous carbon matrix were synthesized by a simple one-step pyrolysis of titanium based metal-organic framework (MOF),NH2-MIL-125(Ti) at 700 ℃ under water vapour atmosphere.Introducing water vapour during the pyrolysis of NH2-MIL-125(Ti) not only functionalizes the derived porous carbon matrix with carboxyl groups but also forms additional oxygen-rich N like interstitial/intraband states lying above the valence band of TiO2 along with the self-doped carbon,which further narrows the energy band gaps of polymorphic TiO2 nanoparticles that enhance photocatalytic charge transfer efficiency.Without co-catalyst,sample N-C-TiO2/CArw demonstrates H2 evolution activity of 426 μmol gcat-1 h-1,which remarkably outperforms commercial TiO2 (P-25) and N-C-TiO2/CAr with a 5-fold and 3-fold H2 generation,respectively.This study clearly shows that water vapour atmosphere during the pyrolysis increases the hydrophilicity of the Ti-MOF derived composites by functionalizing porous carbon matrix with carboxylic groups,as well as enhancing the electrical conductivity and charge transfer efficiency due to the formation of additional localized oxygen-rich N like interstitial/intraband states.This work also demonstrates that by optimizing the anatase-rutile phase composition of the TiO2 polymorphs,tuning the energy band gaps by N/C co-doping and functionalizing the porous carbon matrix in the N-C-TiO2/C nanocomposites,the photocatalytic H2 generation activity can be further enhanced.