Аннотация:New copper oxo-selenite-sulfate Cu4O(SeO3)(SO4)2 was prepared by the reaction of anhydrous CuSO4, CuO, and SeO2 in a sealed silica tube. The compound crystallizes in the triclinic space group, with cell parameters a = 8.379(3)Å, b = 8.402(4) Å, c = 8.497(3) Å, α = 82.988(14) °, β = 61.006(9) °, γ = 62.105(14)°. The selenite-sulfate features open-framework crystal structure with two types of channels, where lone electron pairs of SeO32- groups are located. DFT calculations were made to support this statement and to investigate the nature of chemical bonding in the crystal structure and estimate the band gap (3.3 eV). The crystal structure of Cu4O(SeO3)(SO4)2 was compared to the related triclinic form of Cu4O(SeO3)3. The role of sulfate groups is also discussed.