[Me2NH2]3[In3(BTB)4]·2DMF·2DMA·28H2O (InOF-9) is an anionic indium-organic framework based on nanosized cuboctahedrons, which is sustained by tetrahedral [In(COO)4] nodes and 3-connected tricarboxylates. Although InOF-9 is structurally unstable when exposed to air, it exhibits excellent gas sorption capacity through a supercritical carbon dioxide activation process and selectively encapsulates guest methylene blue cations.