Modulation of Crystallinity and Optical Properties in Composite Materials Combining Iron Oxide Nanoparticles and Dye-Containing Covalent Organic Frameworks

Two series of organic-inorganic composite materials were synthesized through solvothermal imine condensation between diketopyrrolopyrrole dialdehyde DPP-1 and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) in the presence of varying amounts of either amino- or carboxylate-functionalized superparamagnetic iron oxide nanoparticles (FeO). Whereas high FeO loading induced cross-linking of the inorganic nanoparticles by amorphous imine polymers, lower FeO content resulted in the formation of crystalline covalent organic framework (COF) domains. All hybrid materials were analyzed by magnetization measurements, powder X-ray diffraction, electron microscopy, IR and UV/Vis absorption spectroscopy. Crystallinity, chromophore stacking and visible absorption features are directly correlated to the mass fraction of the components, thus allowing for a fine-tuning of materials properties.