1 research outputs found
Insight into the Oriented Growth of Surface-Attached Metal–Organic Frameworks: Surface Functionality, Deposition Temperature, and First Layer Order
The
layer-by-layer growth of a surface-attached metal–organic
framework (SURMOF), [Cu<sub>2</sub>Â(F<sub>4</sub>bdc)<sub>2</sub>Â(dabco)] (F<sub>4</sub>bdc = tetrafluorobenzene-1,4-dicarboxylate
and dabco = 1,4-diazabicyclo-[2.2.2]Âoctane), on carboxylate- and pyridine-terminated
surfaces has been investigated by various surface characterization
techniques. Particular attention was paid to the dependency of the
crystal orientation and morphology on surface functionality, deposition
temperature, and first layer order. For the fully oriented deposition
of SURMOFs, not only a suitable surface chemistry but also the appropriate
temperature has to be chosen. In the case of carboxylate-terminated
surfaces, the expected [100] oriented [Cu<sub>2</sub>(F<sub>4</sub>bdc)<sub>2</sub>(dabco)] SURMOF can be achieved at low temperatures
(5 °C). In contrast, the predicted [001] oriented SURMOF on pyridine-terminated
surface was obtained only at high deposition temperatures (60 °C).
Interestingly, we found that rearrangement processes in the very first
layer determine the final orientation (distribution) of the growing
crystals. These effects could be explained by a surprisingly hampered
substitution at the apical position of the Cu<sub>2</sub>-paddle wheel
units, which requires significant thermal activation, as supported
by quantum-chemical calculations