RESUMEN
A new method to construct hierarchical architectures has been developed by programmed transformation of metal-organic frameworks (MOFs). A MOF precursor was fabricated by reaction of Cu(OAC)2 and 2,5-dihydroxyterephthalic acid (H4DOBDC), which could perform transformation in pure methanol solvent and the sodium dodecyl benzene sulfonate (SDBS) solution of methanol, respectively. Interestingly, two kinds of immersion solutions could induce the transformation of the MOF precursor into MOF-74, which resulted in different morphologies: nanoneedles for the methanol and nanosheets for the SDBS. Herein, nanosheets-mesorods-microcuboid hierarchical quaternary architectures of MOF have been successfully achieved by sequential immersion of the precursor in two kinds of transformation solutions, which demonstrates well-defined hierarchy from the nanoscale to mesoscale to microscale. A unique hierarchical architecture could be recognized as quaternary structures, taking the MOF unit cell as the primary structure, the nanosheets as the secondary structure, the mesorods as the tertiary structure, and the microcuboid as the quaternary structure. Our study indicated the potential of programmed transformation between MOFs in the construction of hierarchical architectures, offering a new approach to sophisticated materials.
RESUMEN
2D metal-organic frameworks (MOFs) are promising 2D materials with a wide range of applications due to their unique physical and chemical properties. However, 2D MOFs are prone to stacking due to their ultrathin thickness, and the high-yield preparation method of 2D MOFs is highly demanded. In this work, a rapid and scalable method is novelistically presented to prepare 2D MOFs with highly colloidal stability and high yield through coordination modulation at room temperature. A well-ordered CuBDC-MBA nanosheet (BDC, 1,4-benzenedicarboxylic; MBA, 4-methoxybenzoic acid) fabricated by introducing MBA as a modulator exhibits extremely stable colloid suspension for 6 months and the yield of well-dispersed CuBDC-MBA is higher than 88.6%. As MBA successfully participates in synthetic coordination of CuBDC-MBA and is presumably installed on the edge of 2D MOFs with low MBA content due to anisotropic growth, CuBDC-MBA and CuBDC are similar with respect to nanosheet morphology, integrated crystal structure, and porosity. Moreover, well-dispersed CuBDC-MBA shows higher catalytic effectiveness for the cycloaddition reaction of CO2 with 1.5 times higher yield than CuBDC. Thus, this method can provide a new idea based on coordination modulation to directly fabricate 2D MOFs with purposeful properties.
