•The nanoparticles of Co0.5Cu0.5SmxFe2-xO4 (CCS) were exploited to remove the noxious Rhodamine B dye from pollutant water.•The STEM-EDX micrographs confirmed the purity and the nanocrystalline nature of the CCS samples.•Mgnetic parameters besides microwave frequency and switching field distributions response were determined by VSM results.•Kubelka and Munk (K-M) theory was utilized the DR measurements, to determine the direct band gap of CCS nanoferrites.•Astonishingly, maximum degradation percentage was aggrandized to be 94.36%, under 270 min, for the nanoferrite with x = 0.15. The nanoparticles of Co0.5Cu0.5SmxFe2−xO4 (0 ≤x ≤ 0.15) (CCS) were synthesized with the citrate combustion approach and then exploited to remove the noxious Rhodamine B (RhB) dye from the pollutant water. Before this mission of RhB disposal began, the CCS ferrite nanoparticles were comprehensively characterized by progressing analysis; as XRD, FTIR, STEM, VSM, DRS. The average crystallite size estimated using Williamson-Hall (W–H) method is in the range (75–45 nm). FTIR spectra exhibits the two finger print bands υ1 (~572) and υ2 (~375) of spinel ferrites. The STEM-EDX micrographs confirmed the purity, nanocrystalline nature of the CCS samples and existence of all the constituents' elements; Co, Cu, Sm, Fe and O ions without any other impurities. A gradual decrease for Ms values is remarked with further Sm3+ ions substitution; from MS= 55.373 emu/g (at x = 0.0) to MS= 43.981 emu/g (at x = 0.15). Coercivity shows a distinct behavior; increased from 892.81 Oe at pristine Co–Cu sample reaching a maximum value 1112.70 Oe (at x = 0.09) and then decreased to 983.09 Oe (for x = 0.15). The microwave frequency of the CCS nanoferrites is in the range 12.25–9.73 GHz. The pristine Co–Cu nanoparticles has band gap 1.57 eV, whereas all Sm3+ substituted nanoferrites have lower band gap values as 1.51, 1.55, 1.44, 1.51 and 1.36 eV with further Sm3+ ion substitution process. The photocatalytic activity of the nano-Co0.5Cu0.5SmxFe2−xO4 catalysts were scrutinized by the degradation of RhB dye using simulated sunlight source. Astonishingly, maximum degradation percentage was aggrandized to be 94.36%, under 270 min, for the nanoferrite with x = 0.15. Therefore, it is concluded that Sm doped Co–Cu nanoferrites is more convenient candidate for wastewater treatment applications besides switching, and high frequency absorption applications in microwave region.