Two-dimensional (2D) graphitic carbon nitrides (g-C3N4) have sparked much interest as photocatalysts. However, they suffer from high activation energy and a low separation rate of photoexcited charge carriers. Here we report a viable strategy to craft one-dimensional carbon nitrides denoted as polymelem (PM). Our PM possesses NH-bridged and the N-bridged tautomers, both of which are π-conjugated polymers based on aromatic tri-s-triazine units, as revealed by solid-state nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and Raman techniques. A 2D 1H double-quantum-single-quantum (DQ-SQ) NMR spectrum illustrates that the 2D architecture of PM is constructed by the formation of interchain N-H···N hydrogen bonds between different 1D PM chains. PM exhibits largely improved photocatalytic efficiency compared to g-C3N4. This can be attributed to the conjugated structures of PM, which are conducive to the decrease in activation energy and separation rate of photogenerated charge carriers.