Embedding Graphene Nanoplates into MIL-101(Cr) Pores: Synthesis, Characterization, and CO₂ Adsorption Studies

Abstract

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.

Strong Influence of Amine Grafting on MIL-101 (Cr) Metal–Organic Framework with Exceptional CO2/N2 Selectivity

“…Adsorption kinetics determines the efficiency of an adsorbent in dynamic processes and its endurance in large adsorbate flow. , Fast adsorption kinetics is one of the most critical properties of adsorbent since it can determine residence time required for the completion of the adsorption process, adsorption bed size, and, consequently, unit capital costs which are all essentially associated with the rate of adsorption. Many researchers have attempted to clarify the information that can be deduced from adsorbent–adsorbate interactions, and consequently a series of established models have been introduced.…”

Research on Metal-organic Frameworks for CO2 Capture

“…The reason why ZJNU-54 exhibits a higher uptake of CO 2 than CH 4 is difference in the isosteric heat of adsorption. The value of isosteric heat of adsorption for CO 2 and CH 4 at low coverage are 24.7 and 16.8 kJ mol -1 , suggesting that CO 2 is adsorbed more strongly in ZJNU-54 than CH 4 . Another strategy is post-synthesis method, that is, to chemically modify MOFs after the formation of MOFs crystals.…”

“…Besides, the Q st value of CO 2 adsorption should be increased to a certain degree that minimized the energy penalty for regeneration. Yeganegi et al have done theoretical study on the effect of lithium cation on the adsorption and sepearation of CO 2 , CH 4 , and H 2 on a Zn 2 (NDC) 2 (diPyNI). The results indicated that the selectivity of CO 2 /H 2 on MOF was higher than that of CO 2 /CH 4 at room temperature and pressure up to 50 bar [16].…”

Methane Adsorption on Carbonaceous Microporous Materials Prepared from Cellulose and Lignin: Equilibrium and Kinetic Studies

“…K F (mmol.g 1 .MPa 1=n ) is the Freundlich constant and n is surface heterogeneity parameter of the solid. The constant K F is an approximate indication of the adsorption capacity, while 1=n is a function of the strength of adsorption [26]. However, K F and n are characteristic parameters of the sorbent-sorbate system that should be determined through tting with the experimental data.…”