Dimensional expansion of 1D zigzag chains to a 2D two-fold interpenetrated metal–organic framework for adsorption of lanthanide cations and white light emission

Abstract

A two-dimensional (2D) layered metal–organic framework (MOF), [Cd(hsb-2)(bdc)·5H₂O]_n (HSB-W10), was constructed from Cd(II) and the mixed ligands of bdc (1,4-benzendicarboxylate) and hydrogenated Schiff base hsb-2 (1,2-bis(4′-pyridylmethylamino)-ethane) under mild conditions. The self-assembly of HSB-W10 was predicted with the help of a dimension expansion strategy. By slowly diffusing Cd(II) into the bdc solution, one dimensional (1D) zigzag [Cd(bdc)]_n chains arranged in a staggered manner were formed, which can be knitted to a 2D two-fold interpenetrated network if a suitable second ligand was employed. When hsb-2 was added as the second ligand, the staggered zigzag Cd-bdc chains were linked together respectively, resulting in the formation of HSB-W10 with a 2D layered structure. Due to its interpenetrated structural features, HSB-W10 exhibited good thermodynamic and chemical stability. HSB-W10 can serve as a host matrix to encapsulate Tb³⁺ and Eu³⁺ for tunable fluorescence emission. White-light emission was also obtained by finely tuning the inclusion amounts of Tb³⁺ and Eu³⁺. 0.064Tb(H₂O)_x³⁺/0.012Eu(H₂O)_x³⁺@HSB-W10 was obtained with the corresponding CIE coordinate of (0.33, 0.29). This work provided a new strategy to fabricate MOFs with the interpenetrated network, which is also beneficial to enhancing the performance of MOFs.