Synthesis of metal-organic framework functionalized macroscopic flow-through precipitate tubes.

The guided growth and the composition control of the well-known chemical garden tubular structures have been widely studied in the literature. However, the applicability of these macroscopic hollow precipitate tubes (e.g., for catalysis, sensorics etc.) is still limited, since these pipes originally do not have a flow-through character, thus the functionalization of these tubes is difficult to implement. In this work, our goal was to design a novel reactor that enables the production of these flow-through precipitate pipes with robust junctions, and thus their functionalization for further applications. We successfully built the reactor and synthesized such pipes. Their flow-through character was proven in case of various template tubes which were produced by injecting one of the reactant solutions into the pool of the other in three dimensions. After the production of the template tubes, we attempted to decorate the surface with sodalite type ZIF-8 crystals, which are of great interest thanks to their beneficial properties (porous structure, huge specific surface area etc.) for catalysis or gas separation. The surface functionalization was carried out by exchanging the reactant solutions inside and outside the template precipitate tubes. Due to the semi-permeable nature of the tube wall, the reactants could diffuse through the membrane and react with each other. This way we produced (most probably sodalite type) ZIF-8 crystals on the inner tube surface and thus functionalized it.