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In this research, the equilibrium and dynamic adsorption studies of the CO2 upon the MIL-101­(Cr) metal–organic framework (MOF) as well as its GNP hybrid composites, the MIL-101­(Cr)/GNP, were performed. First, the hybrid composite samples were synthesized by adding various amounts of GNP in an in situ manner during the preparation of the MIL-101­(Cr). The prepared materials were characterized through several physicochemical analyses, including powder X-ray diffraction (PXRD), adsorption of nitrogen at 77.4 K, Fourier transfer infrared (FT-IR) spectroscopy, thermal analysis (DTG), and field emission scanning electron microscopy (FESEM). It was demonstrated that the synthesized MIL-101­(Cr)/GNP possessed a nearly similar crystal structure and morphology compared with those of the virgin sample. Next, the CO2 adsorption studies upon these sorbents were performed through a volumetric adsorption apparatus at 298 K and CO2 pressures of up to 40 bar using an in-house made rig. It was shown that the CO2 adsorption capacity was enhanced by about 43% (i.e., from 14.38 to 20.62 mmol·g–1) for the hybrid composite containing 10 wt % of the GNP compared to the virgin MIL at 298 K and 40 bar. This enhancement in the CO2 adsorption capacity was attributed to the effect of the GNP embedded into the internal MIL-101­(Cr) pores giving rise to stronger interactions between the walls of this species and CO2 molecules. Furthermore, increase of the specific surface area as well as total and micropore volumes of the MIL-101­(Cr) was rationalized to be due to this GNP addition. Ultimately, in order to mechanistically understand the adsorbents’ behaviors, several kinetic and isotherm models were studied. It was revealed that the FL-PFO and dual site Toth relationships outstandingly described the CO2 adsorption upon the sorbents.

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Kraft lignin has been widely investigated for the production of composite plastics by blending with different synthetic polymers. In the present study, softwood kraft lignin-polyethylene (PE) composites are produced by extrusion. The change in lignin structure during the extrusion has been investigated and the influences of the lignin structure change on the properties and recyclability of the composites have been investigated. Extrusion reduces the content of