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

Novel kind of molybdenum(VI/V) POM-based self-constructed frameworks [MoVI12O24(μ2-O)12(trz)6(H2O)6]∙6Hma∙18H2O (1, Htrz = 1H-1,2,3-triazole, ma = methylamine), [MoVI7O14(μ2-O)8(trz)5(H2O)]∙7Hma∙5H2O (2), Na3[MoV6O6(μ2-O)9(Htrz)3(trz)3]∙7.5H2O (3) and [MoV8O8(μ2-O)12 (Htrz)8]∙30H2O (4) were covalently decorated with tri-coordinated deprotonated/protonated 1,2,3-triazoles respectively. Channels with 7.5 A inner diameter have been found in 1, while a tunnel composed of molecules stacking with an inner diameter of 4.1 A in b axis lives in 2, which is occupied by free disordered methylamines, showing selective adsorptions of O2 and CO2 at 25 oC. Obvious downfield shifts have been observed for methylamines inside the confined channels in 1 and 2 with 13C NMR measurements. There are diversified pores in 3 and 4, which are formed by molecules themselves and intermolecular accumulations. Adsorption tests indicate that 3 and 4 are fancy adsorption materials for CH4 and CO2 under low pressure relied on the environments built by POMs. Correspondingly, 1 and 2 display reversible photoresponsive thermochromisms which are subtlety influenced by channels. The polyoxometalate organic frameworks (POMOFs) with multiple functional adsorptions are easy for assemblies. Their photo/thermo-responded properties offer a fire-new pathway for the self-constructions of one-off hybrid materials, which possess both nice properties of POM and MOF simultaneously.