A simplistic, elegant approach has been invoked for the gram level synthesis of cubooctahedral Zn₃V₂O₈ without the assistance of any template or growth directing agent. By heating on a water bath, ZnSO₄ and ammonium vanadate produce unique cubooctahedral Zn₃V₂O₇(OH)₂(H₂O)₂. Then, cubooctahedral Zn₃V₂O₈ is generated upon heating Zn₃V₂O₇(OH)₂(H₂O)₂ at a temperature of 500 °C in air. Interestingly, the morphology of Zn₃V₂O₇(OH)₂(H₂O)₂ remains unaltered even after complete dehydration by heat treatment. The unusual robust morphology of Zn₃V₂O₈ exhibits enhanced photocatalytic dye mineralization activity, leaving behind Zn₃V₂O₇(OH)₂(H₂O)₂ and also NH₄VO₃. Cationic, nonionic and anionic dye degradation has become effective with a high turn over number (TON). The synthesized nanomaterial, being robust and highly photoactive, finds valuable application in environmental remediation under UV irradiation. In a nutshell, the present work provides some new insights for a low-cost and high-yielding greener synthetic protocol to produce a well defined photocatalytic material bearing a unique structure to benefit potential applications in wastewater treatment.