Engineering nanospaces: OMS/dendrimer hybrids possessing controllable chemistry and porosity

The synthesis and characterization of melamine-based dendrimer/SBA-15-hybrids are reported. The current work demonstrates the ability to fabricate hybrid materials containing a high loading of organic moieties (similar to 30-35 wt %) that possess a well-defined structure. Numerous characterization methods including X-ray diffraction, electron microscopy, infrared spectroscopy, solid-state NMR spectroscopy, thermal gravimetric analysis, MALDI-MS, elemental analysis, and nitrogen porosimetry have been used to characterize the microstructure of the hybrids obtained. On the basis of thermal gravimetric analysis and elemental analysis, the average conversion between generations is between 70 and 75% and highly reproducible. MALDI-MS verifies that a significant fraction of the organic groups on the OMS surface possesses the desired structure, consistent with IR and NMR results. The porosity of the hybrid can be modified either by using dendrimers of different generations, using different linkers in the dendrimer structure, or by controlling dendrimer loading. Porosimetry measurements indicate that the effective pore size of the hybrid and the total pore volume of the material can be controlled independently of one another. Copper sequestration was used as a probe to demonstrate that the amines of the dendrimer are accessible and able to bind Cu( II). Given the ability to tune chemistry and porosity independently, the current work shows that these hybrid materials have potential uses in many areas including separations, sensing, and catalysis.