MOF/graphite oxide hybrid materials: exploring the new concept of adsorbents and catalysts

Two types of metal-organic framework (MOF)/graphite oxide hybrid materials were prepared. One is based on a zinc-containing, MOF-5 and the other on a copper-containing HKUST-1. The materials are characterized by X-ray diffraction, sorption of nitrogen, thermal analyses, Fourier Transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Their features are compared to the ones of the parent materials. The water stability and ammonia adsorption capacity of the hybrid materials were also evaluated. It was found that the latter compounds exhibit features similar to the ones of the parent MOF. In most cases, their porosity increased compared to the one calculated considering the physical mixture of MOF and GO. This new porosity likely located between the two components of the hybrid materials is responsible for the enhanced ammonia adsorption capacity of the compounds. However, for both the zinc-based and the copper-based materials (MOFs and hybrid materials), a collapse of the framework was observed as a result of ammonia adsorption. This collapse is caused by the interactions of ammonia with the metallic centers of MOFs either by hydrogen bonding (zinc-based materials) or coordination and subsequent complexation (copper-based materials). Whereas the MOF-5 based compounds collapse in presence of humidity, the copper-based materials are stable.