A novel Co(II) complex [Co4(HL)2Phen2(H2O)10]·20(H2O) (HL = 5-(Bis-carboxymethyl-amino)-isophthalic acid; Phen = 1,10-Phenanthroline) was synthesized by hydrothermal methods, and its crystal structure was determined by single-crystal X-ray diffraction. The title complex crystallized in the monoclinic space group C2/c as an isolated tetranuclear structure. The strong π···π stacking, hydrogen bonding and van de Waals attractions produce 3D supramolecular structure. A series of properties of the title complex were tested by solid-state photoluminescence, CIE analysis and solid-state diffuse reflectance. The results show that the title complex is blue light emitter, CIE (0.2172, 0.5581) and has an energy bandwidth of 2.33 eV.Graphical Abstract: A novel monoclinic space group C2/c complex of [Co4(L)2Phen2(H2O)10]·20(H2O) (HL = 5-(Bis-carboxymethyl-amino)-isophthalic acid; Phen = 1,10-Phenanthroline) was synthesized by hydrothermal methods, and a series of properties of the complex were tested by solid-state photoluminescence, CIE analysis and solid-state diffuse reflectance, which results show that the title complex is blue light emitter, CIE (0.2172, 0.5581) and has an energy bandwidth of 2.33 eV.