Lanthanum-substituted CaMo-MOF via controlled metal nitrate ratios for Electrochemical Performance

• Synthesized LaₓCa 1-x Mo-based MOFs with a single-phase tetragonal scheelite-type structure. • Demonstrated crystallite size reduction (54 → 16 nm) with morphological transition from irregular granules to well-faceted rods. • Achieved superior electrochemical performance in CML3 MOF, showing the highest current density in CV curves. In this study, a series of LaₓCa 1-x Mo-based metal-organic frameworks (MOFs), designated as CML1, CML2, CML3, and CML4, were synthesized via a controlled precipitation method. A comprehensive characterization was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XRD confirmed the formation of a single-phase tetragonal scheelite-type structure (I4₁/a), with no secondary phases detected. The average crystallite size is found to be 54, 52, 42 and 16 (nm) in CML1, CML2, CML3 and CML4 MOFs. The SEM reveals a morphological evolution from irregular granules in CML1 to well-faceted rods in CML4 MOFs. The electrochemical analysis revealed a clear performance hierarchy, with CML3 electrode exhibiting the highest current density, the narrowest redox peak separation in the CV curve in a three and two-electrode system. The coulombic efficiency of 96 % is retained by the CML3 electrode even after 1000 GCD cycles in a two-electrode system.