An unprecedented 4f-5d material (La6Hg5Br26)[4(HgBr2)](2Br) (1) was synthesized by hydrothermal reactions and structurally characterized by single-crystal X-ray diffraction method.Complex 1 crystallizes in the Pbam space group of orthorhombic system with a =13.0980(10),b =13.6650(9),c =28.010(2) (A),V=5013.4(6) (A)3,Br36Hg9La6,Mr =5515.53,Z=2,Dc =3.613 g/cm3,μ(MoKα) =29.457 mm-1 and F(000) =4598.Compound 1 is characteristic of a two-dimensional (2D) layered structure.The photoluminescent measurements with solid-state samples reveal that compound 1 has a strong emission in the green region of light spectrum.It has remarkable CIE chromaticity coordinates of (0.2499,0.3589).A wide optical band gap of 3.41 eV is discovered by the solid-state UV/vis diffuse reflectance spectrum.The variable-temperature magnetic susceptibility obeys the Curie-Weiss law (χm =c/(T-θ)) with C =2.48 K and a negative Weiss constant θ =-169.07 K as revealed by the magnetic measurements,indicating the existence of an antiferromagnetic interaction in compound 1.