CO₂ Capture and Gas Storage Capacities Enhancement of HKUST-1 by Hybridization with Functionalized Graphene-like Materials

Abstract

The role of graphene related material (GRM) functionalization on the structural and adsorption properties of MOF-based hybrids was deepened by exploring the use of three GRMs obtained from the chemical demolition of a nanostructured carbon black. Oxidized graphene-like (GL-ox), hydrazine reduced graphene-like (GL), and amine-grafted graphene-like (GL-NH 2 ) materials have been used for the preparation of Cu-HKUST-1 based hybrids. After a full structural characterization, the hybrid materials underwent many adsorption−desorption cycles to evaluate their capacities to capture CO 2 and store CH 4 at high pressure. All the MOF-based samples showed very high specific surface area (SSA) values and total pore volumes, but different pore size distributions attributed to the instauration of interactions between the MOF precursors and the specific functional groups on the GRM surface during MOF growth. All the samples showed a good affinity toward both gases (CO 2 and CH 4 ) and a comparable structural stability and integrity (possible aging was excluded). The trend of the maximum storage capacity values of the four MOF samples toward CO 2 and CH 4 was HKUST-1/GL-NH 2 > HKUST-1 > HKUST-1/GL-ox > HKUST-1/GL. Overall, the measured CO 2 and CH 4 uptakes were in line with or higher than those already reported in the open literature for Cu-HKUST-1 based hybrids evaluated in similar conditions.

Metal-organic frameworks as photocatalysts in energetic and environmental applications

“…High surface area, structural designability, tunable pore channels, high surface-to-volume ratios, flexibility to be functionalized with different ligands and metal centers which can be extended up to 90% of the crystal volume, and rich compositions are just a few of the extraordinary features of MOFs structures [ 8 – 11 ]. These distinctive characteristics depict MOFs as porous network architectures, which have drawn significant research interest in a number of potential application areas, including gas storage [ 12 ], separation [ 13 ], drug delivery [ 14 ], sensing [ 15 ], nonlinear optics [ 21 ], luminosity [ 22 ], heterogeneous catalysis [ 23 ], photocatalysis [ 24 ], and carbon capture and transformation [ 25 , 26 ].…”

“…MOFs with a well-defined crystalline structure are a class of highly porous materials that have shown great potential in photocatalytic applications for energetic and environmental purposes [ 30 ]. Due to their large surface area and tunable pore sizes, MOFs can be used for various applications [ 12 – 15 , 21 – 26 , 31 , 32 ]. As photocatalysts, one of the most promising applications of MOFs is in the fields of energy conversion [ 33 ].…”

“…Additionally, the organic ligands can be functionalized with electron-donating or electron-withdrawing groups to alter the electronic characteristics of MOFs, or the MOFs can be doped with guest molecules. This can change the band gaps and band locations of MOFs, making them better suited for particular applications [ 9 – 12 ]. MOFs offer a number of methods for producing photocatalytic activity, as opposed to conventional semiconductor materials, which frequently rely on surface modification by noble metal nanoparticles or transition metal complexes to produce tunability ( Figure 2 ) [ 51 ].…”

“…While the optical response can be changed by modifying the cluster-forming metal or employing mixed metal clusters, the reductive power can also be changed by choosing metal ions with the appropriate orbitals. Overall, MOFs are attractive materials for a variety of optoelectronic applications due to their unique advantages as semiconductors, such as their enormous surface area, porosity, and tunable electronic characteristics [ 1 – 4 , 8 – 12 , 17 , 51 ].…”

“…MOFs were generally used as efficient photocatalysts due to their features such as functional organic linkers, the large surface area and permanent porosity, the richness of metal-containing secondary building units (SBUs) as catalytically active sites, and a tuneable band gap [ 9 – 12 , 51 ].…”