Intrinsic Molybdenum-Based POMOFs with Impressive Gas Adsorptions and Photochromism.

Novel molybdenum(VI/V) POM-based self-constructed frameworks [MoVI 12 O24 (μ2 -O)12 (trz)6 (H2 O)6 ] ⋅ 6Hma ⋅ 18H2 O (1, Htrz=1H-1,2,3-triazole, ma=methylamine), [MoVI 7 O14 (μ2 -O)8 (trz)5 (H2 O)] ⋅ 7Hma ⋅ 5H2 O (2), Na3 [MoV 6 O6 (μ2 -O)9 (Htrz)3 (trz)3 ] ⋅ 7.5H2 O (3) and [MoV 8 O8 (μ2 -O)12 (Htrz)8 ] ⋅ 30H2 O (4) have been covalently decorated with tri-coordinated deprotonated/protonated 1,2,3-triazoles. Channels with an inner diameter of 7.5 Å were found in 1, whereas a tunnel composed of stacking molecules with an inner diameter of 4.1 Å along the b-axis exists in 2; it is occupied by free disordered methylamines, showing selective adsorption of O2 and CO2 at 25 °C. Obvious downfield shifts were observed by 13 C NMR spectroscopies for methylamines inside the confined channels in 1 and 2. There are diversified pores in 3 and 4, which are formed by the molecules themselves and intermolecular accumulations. Adsorption tests indicate that 3 and 4 are fine adsorption materials for CH4 and CO2 under low pressure that rely on the environments built by the POMs. Correspondingly, 1 and 2 display reversible photoresponsive thermochromism that is subtlety influenced by the channels. The polyoxometalate organic frameworks (POMOFs) with multiple functional adsorptions are easy to assemble. Their photo-/thermoresponse properties offer a new pathway for the self-constructions of one-off hybrid materials that possess the good properties of both POMs and MOFs.