Two New Copper Borates with Mesoscale Cubic Supramolecular Cages Assembled from {Cu₄@B₂₀} Clusters

Two new copper borates, namely H₆[(μ₄-O)Cu₄@B₂₀O₃₂(OH)₈]⋅25 H₂O (1) and H₆[(μ₄-O)Cu₄@B₂₀O₃₂(OH)₈]⋅34 H₂O⋅8 H₃BO₃ (2), with 3D supramolecular framework have been made under solvothermal conditions, which built by novel cubic supramolecular cages with mesoscale cavities via the H-bondings. Interestingly, the cage is assembled by [(μ₄-O)Cu₄@B₂₀O₃₂(OH)₈] ({Cu₄@B₂₀}) cluster units with different point-group symmetry. Owing to extra H₃BO₃ molecules participated in building the supramolecular framework, 2 has a larger cubic cage size and higher non-framework volume, leading to the cage size extended to mesoporous size set as a version of ‘‘1 plus”.