Reactive adsorption of acidic gases on MOF/graphite oxide composites

Composites were prepared from metal–organic framework (MOF; copper-containing HKUST-1) and graphite oxide (GO). The synthesized materials were tested as adsorbents of hydrogen sulfide (H2S) and nitrogen dioxide (NO2). Their surface was characterized using nitrogen adsorption, Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The results indicate that formation of new small pores in the composites has a positive effect on the adsorption capacity of both acidic species. Physisorption and reactive adsorption are suggested as main adsorption mechanisms. The latter mechanism is related to the presence of unsaturated copper sites in the MOF structure, which bind H2S and NO2 molecules. This process is followed by further reactions with the MOF network leading to the formation of either copper sulfide or copper nitrate. Although the overall scheme of adsorption process appears to be similar for both H2S and NO2 adsorption, the importance of the surface features governing these mechanisms appears to be different. Consequently, different trends in the performance of HKUST-1 and the composites are observed.