Enhanced CO2 adsorption performance on amino-defective UiO-66 with 4-amino benzoic acid as the defective linker

Facile synthesis of Fe-based metal-organic frameworks from Fe2O3 nanoparticles and their application for CO2/N2 separation

A facile approach was employed to fabricate MIL-100(Fe) materials from Fe2O3 nanoparticles through a conventional hydrothermal reaction without the presence of HF and HNO3. Effects of trimesic acid content in the reaction system on the quality and CO2/N2 separation performance of the as-prepared MIL-100(Fe) samples were investigated. Using 1.80 g of trimesic acid in the reaction system yielded the sample M-100Fe@Fe2O3#1.80, which proved to be the optimal sample. This choice struck a balance between the amount of required trimesic acid and the quality of the resulting material, resulting in a high yield of 81% and an impressive BET surface area of 1365.4 m2·g-1. At 25 °C and 1 bar, M-100Fe@Fe2O3#1.80 showed a CO2 adsorption capacity of 1.10 mmol·g-1 and an IAST-predicted CO2/N2 selectivity of 18, outperforming conventional adsorbents in CO2/N2 separation. Importantly, this route opens a new approach to utilizing Fe2O3-based waste materials from the iron and steel industry in manufacturing Fe-based MIL-100 materials.

Effect of benzoic acid and dopamine hydrochloride as a modulator in the water resistance of Universitetet i Oslo-67: Adsorption performance and mechanism

The severe hazards on ecological environment and human body caused by volatile organic compounds (VOCs) have attracted worldwide substantial attention. In this research, a series of novel modified Universitetet i Oslo-67 (UiO-67) with water resistance were prepared and characterized, which had modified by benzoic acid and dopamine hydrochloride (67-ben-DH). On this basis, the adsorption performance, adsorption kinetics, defect engineering and water resistance of adsorbent were investigated. The results indicated that the excellent pore structure and specific surface area of 67-ben-DH-6 (molar ratio of Zr4+ to DH was 1:6) were retained while the adsorption performance and water resistance of the adsorbent were improved. Due to more defects, excellent adsorption diffusion and strong π-π interactions of 67-ben-DH-6, it performed the maximum adsorption capacity of toluene (793 mg g-1). Furthermore, the outstanding water resistance was attributed to the fact that N element of DH reduced the affinity of the adsorbent with water. Finally, the density functional theory (DFT) calculations showed that the adsorbent 67-ben-DH-6 had the maximum adsorption energy for toluene (-99.4 kJ mol-1) and the minimum adsorption energy for water (-17.8 kJ mol-1). Thus, the potential mechanism of 67-ben-DH for efficient toluene adsorption and water resistance was verified from a microscopic perspective.

Zn-Based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties

A series of metal-organic frameworks (MOFs) based on zinc ions and two triptycene ligands of different size have been synthesized under solvothermal conditions. Structural analyses revealed that they are isostructural 3D-network MOFs. The high porosity and thermal stability of these MOFs can be attributed to the highly rigid triptycene-based ligands. Their BET specific surface areas depend on the size of the triptycene ligands. In contrast to these surface-area data, the H2 and CO2 adsorption of these MOFs is larger for MOFs with small pores. Consequently, we introduced functional groups to the bridge-head position of the triptycene ligands and investigated their effect on the gas-sorption properties. The results unveiled the role of the functional groups in the specific CO2 binding via an induced interaction between adsorbates and the functional groups. Excellent H2 and CO2 properties in these MOFs were achieved in the absence of open metal sites.

Selectivity of MOFs and Silica Nanoparticles in CO2 Capture from Flue Gases

Until reaching climate neutrality by attaining the EU 2050 level, the current levels of CO2 must be mitigated through the research and development of resilient technologies. This research explored potential approaches to lower CO2 emissions resulting from combustion fossil fuels in power plant furnaces. Different nanomaterials (MOFs versus silica nanoparticles) were used in this context to compare their effectiveness to mitigate GHG emissions. Porous materials known as metal-organic frameworks (MOFs) are frequently employed in sustainable CO2 management for selective adsorption and separation. Understanding the underlying mechanism is difficult due to their textural characteristics, the presence of functional groups and the variation in technological parameters (temperature and pressure) during CO2-selective adsorption. A silica-based nanomaterial was also employed in comparison. To systematically map CO2 adsorption as a function of the textural and compositional features of the nanomaterials and the process parameters set to a column-reactor system (CRS), 160 data points were collected for the current investigation. Different scenarios, as a function of P (bar) or as a function of T (K), were designed based on assumptions, 1 and 5 vs. 1-10 (bar) and 313.15 and 373.15 vs. 313.15-423.15 (K), where the regression analyses through Pearson coefficients of 0.92-0.95, coefficients of determination of 0.87-0.90 and p-values < 0.05, on predictive and on-site laboratory data, confirmed the performances of the CRS.

Improvement of water adsorption performance of UiO-66 by post-synthetic modification

Post-synthetic modification can be used for structural replacement or functional modification of materials after they have been formed or assembled. It can effectively combine various modification methods for metal-organic frameworks (MOFs) such as defect control, replacement of metal sites, or functionalization of ligands. In this work, organic ligands that incorporate N-functionalities or amino groups were introduced into defective UiO-66 through post-synthetic ligand exchange (PSE) to improve its water adsorption performance. Parameters such as water adsorption capacity, half adsorption value (α), and Henry constant KH were used to characterize the water adsorption performance. After PSE, new ligands in different molar ratios entered the skeleton of UiO-66. The N sites or amino groups on the ligands provided new sites for the adsorption of water molecules. The water adsorption capacity and hydrophilicity of all samples were significantly superior to those of LD-UiO-66, which had almost no defects. H-UiO-66-PyDC samples exhibited the highest ligand replacement ratio and a significant enhancement of water adsorption performance. Compared to the unchanged H-UiO-66, the water uptake of H-UiO-66-PyDC increased from 0.08 g g-1 to 0.23 g g-1 at P/P0 = 0.30 and α decreased from 0.36 to 0.28. After 20 water adsorption/desorption tests, the water uptake of all samples did not decrease, showing excellent cycling stability. These results suggest that the combination of defect modulation and PSE is a potential tool to make UiO-66 more appropriate for applications based on reversible adsorption.

Vapor-assisted crystallization of in situ glycine-modified UiO-66 with enhanced CO2 adsorption

Vapor consisting of DMF and HCl promotes crystallization of in situ glycine-modified UiO-66.