New class of superlattice nanohybrids of interstratified graphitic-carbon nitride (g-C3N4)-transition metal dichalcogenide monolayers are synthesized by employing pH-controlled g-C3N4 nanosheet (NS) as an emerging cationic building block. The interstratification of g-C3N4 and MoS2 NSs leads to strong interfacial electronic coupling, creation of nitrogen vacancy, and stabilization of 1T'-MoS2 phase. The superlattice g-C3N4-MoS2 nanohybrids display remarkably enhanced bifunctionality as photocatalysts for visible light-induced N-2 fixation and electrocatalysts for hydrogen evolution. Of prime importance is that the creation of nitrogen vacancy results in the significant improvement of selectivity for photocatalytic N-2 fixation (582 mu molL(-)(1)h(-1)) over competitive photocatalytic H-2 generation. This is attributable to promoted adsorption of nitrogen, provision of many active sites, and enhancement of charge transfer kinetics, charge separation, and visible light absorptivity. This study highlights that the application of g-C3N4 NS as a cationic building block provides valuable opportunity to widen the library of multifunctional NS-based superlattice nanohybrids.