A simple and cost-effective approach was reported for fabrication of a novel highly efficient combination of 1D-2D g-C3N4 heterojunction nanophotocatalyst (C3N4(1D-2D)) through condensation of protonated melamine by HNO3 in different solvents (water and ethanol). Structural and optical features of the samples were characterized by various physicochemical and electrochemical techniques. The results revealed utilization of ethanol as solvent instead of water completely altered the morphology of g-C3N4 from porous laminar structure (C3N4(2D)) to fibrous structure (C3N4(1D)), while leading to g-C(3)N(4)( )samples with different band gaps and energy band edges. The results of FESEM, PL, transient photocurrent and EIS nyquist measurements of C3N4(1D-2D) revealed a unique multidimensional structure, appropriate matched energy levels, excellent interfacial contact and significant charge recombination quenching, which suggested composite system as an efficient visible-lightdriven photocatalyst. Additionally, C3N4(1D-2D) isotype heterojunction exhibited significantly enhanced photoactivity toward H-2 evolution through water splitting under visible light irradiation by 2.6 and 4.1 times in comparison to individual C3N4 (1D) and C3N4(2D), respectively. This enhancement of photocatalytic activity of C3N4(1D-2D) was mainly ascribed to the efficient charge carrier separation and facile migration across the intimate interfacial of heterojunction by the well matched energy levels. The current study is expected to provide a new framework towards rational design of more efficient metal free based photocatalysts and dissimilar dimensional isotype heterojunction systems for solar energy utilization. (C) 2018 Elsevier Ltd. All rights reserved.