Herein bimetallic nanoparticles of Co–Mn were prepared using metal-organic framework (CoMn2 (C2O4)3·6H2O) as a starting material. Initially, the bimetallic organic frame work was prepared which was then subjected to pyrolysis to get the desired product. Techniques like scanning electron microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were used to characterize the bimetallic nanoparticles. These analyses revealed that the Co–Mn nanoparticles consisted of finely distributed Mn and Co, along with O in the composites. XRD data confirmed the presence of nano-scale ranges and alloy formation between Co–Mn. The nanoparticles were employed as adsorbent for methyl violet adsorption, with optimized conditions found to be pH 9, temperature 333 K, adsorbents dosage of 0.01 g, and 30 min of contact time. The pseudo-second-order kinetic model best described the adsorption kinetics data whereas Langmuir isotherm exhibited the closest fit, with a maximum adsorption capacity of 625 mg/g at 333 K. Thermodynamic parameters indicated endothermic processes, with ΔH° = 15.155 kJ mol−1, and the process to be spontaneous with negative ΔG° values −0.303, −0.831, and −1.886 (kJ mol−1) at 293 K, 313 K, and 333 K, respectively. The ΔS° value of 52.76 J mol−1K−1 suggested increased disorder at the solid-solution interface during adsorption. The adsorbent could be effectively used in reclamation of dyes loaded water as alternative of activated carbon.