Facile Cu(I) Loading for Adsorptive C 3 H 6 / C 3 H 8 Separation Through Double Cu( II ) Salts Incorporation Within Pores With Unsaturated Fe( II ) Sites

Large-Scale Computational Screening-Aided Development of High-Performance Adsorbent for Simultaneous Capture of Aromatic Volatile Organic Compounds

The development of an efficient adsorbent for the simultaneous capture of large amounts of benzene, toluene, ethylbenzene, and xylene isomers (BTEX) is an important and challenging issue. Here, through a stepwise screening of 10,142 metal-organic framework (MOF) structures from the computation-ready, experimental (CoRE) MOF database, 65 MOFs are proposed as promising adsorbent candidates for BTEX capture by considering the structures with accessible pore sizes for BTEX adsorption, sufficient hydrophobicity, high benzene selectivity (>0.2), and large total BTEX uptake (>3 mmol/g). Among the top-performing MOFs in terms of the BTEXmatrix (total BTEX uptake × benzene selectivity), EGUELUY01 was synthesized, and it exhibited large uptakes (≈5 mmol/g) for all BTEX components at concentrations of 1200-1500 ppm, which are superior to the BTEX uptake of the benchmark adsorbent, activated carbon. Moreover, some structure-property relationships required for BTEX adsorbents are provided through the obtained large-scale simulation data and machine learning analysis. The determined relationships will be useful for the future development of efficient BTEX adsorbents.

Water-Stable Microporous Bipyrazole-Based Framework for Efficient Separation of MTO Products

Recently, methanol-to-olefins (MTO) technology has been widely used. The development of new adsorbents to separate MTO products and obtain high-purity ethylene (C2H4) and propylene (C3H6) has become an urgent task. Herein, an exceptionally highly water-stable metal-organic framework (MOF), [Cu3(OH)2(Me2BPZ)2]·(solvent)x (1) (H2Me2BPZ = 3,3'-dimethyl-1H,1'H-4,4'-bipyrazole) with hexagonal pores, has been elaborately designed and constructed. After being soaked in water for 7 days, it still maintains its structure, and the uptake of N2 at 77 K is unchanged. The adsorption capacity of C3H6 can reach 138 cm3 g-1, while the uptake of C2H4 is only 52 cm3 g-1 at 298 K and 1 bar. The dynamic breakthrough experiments show that the mixture of C3H6/C2H4 (50/50, v/v) can be efficiently separated in one step. High-purity C2H4 and C3H6 can be obtained through an adsorption and desorption cycle and the yields of C2H4 (purity ≥ 99.95%) and C3H6 (purity ≥ 99%) are 84 and 48 L kg-1, respectively. Surprisingly, when the flow rate is increased, the separation performance has no obvious change. Additionally, humidity has no effect on the separation performance. Finally, theoretical simulations indicate that there are stronger interactions between the C3H6 molecule and the framework, which are beneficial to capturing C3H6 over C2H4.

Na4P2O7-Modified Biochar Derived from Sewage Sludge: Effective Cu(II)-Adsorption Removal from Aqueous Solution

With the rapid development of industrialization, the amount of copper-containing wastewater is increasing, thereby posing a threat to the aquatic ecological environment and human health. Sludge biochar has received extensive concern in recent years due to its advantages of low cost and sustainability for the treatment of heavy-metal-containing wastewater. However, the heavy-metal-adsorption capacity of sludge biochar is limited. This study prepared a sodium pyrophosphate- (Na4P2O7-) modified municipal sludge-based biochar (SP-SBC) and evaluated its adsorption performance for Cu(II). Results showed that SP-SBC had higher yield, ash content, pH, Na and P content, and surface roughness than original sewage sludge biochar (SBC). The Cu(II)-adsorption capacity of SP-SBC was 4.55 times than that of SBC at room temperature. For Cu(II) adsorption by SP-SBC, the kinetics and isotherms conformed to the pseudo-second-order model and the Langmuir–Freundlich model, respectively. The maximum adsorption capacity of SP-SBC was 38.49 mg·g−1 at 35°C. Cu(II) adsorption by SP-SBC primarily involved ion exchange, electrostatic attraction, and precipitation. The desired adsorption performance for Cu(II) in the fixed-bed column experiment indicated that SP-SBC can be reused and had good application potential to treat copper-containing wastewater. Overall, this study provided a desirable sorbent (SP-SBC) for Cu(II) removal, as well as a new simple chemical-modification method for SBC to enhance Cu(II)-adsorption capacity.

Breathing-Assisted Selective Adsorption of C8 Alkyl Aromatics in Zn-Based Metal-Organic Frameworks

The breathing phenomenon in metal-organic frameworks (MOFs) has revealed supramolecular host-guest interactions that could be beneficial for chemical separation in numerous industrial applications. The cost-effective purification of C₈ alkyl aromatics such as o-xylene, m-xylene, p-xylene, and ethylbenzene remains challenging owing to their similar molecular structures, boiling points, kinetic diameters, polarities, etc. Herein, we report two Zn-based pillar-bilayered MOFs, denoted [Zn₂ (aip)₂ (pillar)] (aip=5-aminoisophthalic acid; pillar: bpy=4,4'-bipyridine or bpe=1,2-bis(4-pyridyl)ethane) that exhibit a breathing effect depending on the adsorbed guest molecules. Guest-dependent sorption studies in organic solvents such as N,N-dimethylformamide, methanol, benzene, and water vapor display reversible structural flexibility through the breathing effect in both framework compounds. The experiments conducted on C₈ -alkyl aromatics resulting in both MOF compounds can access these isomers in the shrunken pores, and thereby expand the pore size by framework breathing. In C₈ binary mixtures, these Zn-MOFs exhibit selective sorption properties based on the different interactions between guest C₈ aromatics and the framework structure.