RESUMO
Metal-organic frameworks (MOFs) have been recognized as a potential platform for the development of tunable luminophores owing to their highly modulable structures and components. Herein, two MOF luminophores based on Cd(II) ions, 1,3,5-tri(4-pyridinyl)benzene (TPB), and 1,4-dicarboxybenzene (H2BDC) were constructed. The directed assembly of the metal ions and organic linkers results in [Cd2(BDC)2(TPB)(H2O)]·x(solvent) (MOF-1) featuring TPB-based blue fluorescence centered at 425 nm. By introducing anthracene as the structure directing agent (SDA) for assembly regulation, [Cd2(BDC)(TPB)2(NO3)2]·x(solvent) (MOF-2) was obtained, which reveals anthracene feeding-dependent high tunable emission in the 517-650 nm range. Detailed components, photophysical properties, and structural characteristics investigations of MOF-2 indicate the TPB and NO3- interactions as the origin of its redshifted emission compared with that of MOF-1. Furthermore, the fluorescence of MOF-2 was found to be regulatable by the anthracene feeding based on the SDA-determined crystallinity of the crystalline sample. All these results provided a unique example of the structural and fluorescence regulation of MOF luminophores.
RESUMO
The hierarchical porous metal-organic framework (HP-MOF) has emerged as a hot topic in porous materials in consideration of their advantages in storage capacity and catalysis performance. Herein, we report the construction and property investigation of a series of HP-MOFs. A series of isoreticular microporous MOFs featuring the pacs topology network based on 2,4,6-tris(4-pyridyl)-1,3,5-triazine and different carboxylic acid ligands are found to be potential precursors to construct HP-MOFs. Through the decarboxylation of carboxylate ligands at high temperatures, a hierarchical porous structure could be obtained with the reservation of a crystalline framework. The formation of hierarchical pores is highly dependent on the structural and component nature (carboxylate ligands and metal centers) of the pristine MOF and the pyrolysis conditions (temperature and treatment time), indicating the highly tunable hierarchical pore characteristic of the HP-MOFs. By taking advantage of the increased pore volume and more exposed activation sites, the HP-MOFs reveal enhanced anionic dye adsorption capacity (800 mg·g-1 for Congo red and 140 mg·g-1 for methyl blue) and catalytic activity toward electrocatalytic oxygen reduction reaction (overpotential of 0.302 V at a current density of 10 mA·cm-2, 51 mV lower than that of the pristine MOF).
RESUMO
The construction and modulation of hierarchical pore structure in metal-organic frameworks (MOFs) has become a hot topic owing to the advantages of hierarchical pore MOFs (HP-MOFs) in matter storage and mass transfer related applications. Herein, we report the engineering of crystalline defect in a bimetallic MOF for the construction and tuning of HP-MOF. A microporous MOF system showing metal-center-dependent water stability, namely, {[M3F(bdc)3 tpt] (solvents)}n (M = Zn2+ and Ni2+, H2bdc = 1,4-benzenedicarboxylic acid, tpt = 2,4,6-tris(4-pyridyl)triazine), was utilized as a platform for the construction of HP-MOF. By tuning the Zn2+/Ni2+ ratio in the reactant, a bimetallic MOF with a highly tunable Zn2+/Ni2+ ratio could be obtained. The relatively labile Zn2+-based coordination bonding in the bimetallic MOF could be readily and targeted broken through water treatment for the engineering of crystalline defects-based hierarchical pore structure. The resultant HP-MOF reveals a dramatically increased pore volume with the presence of mesopore and macropore. In addition, the anionic framework of HP-MOF could be utilized for the selective adsorption of a cationic dye methylene blue, and a relatively high capacity (250 mg·g-1, five times compared with the pristine microporous MOF) could be achieved.
