Biased adsorption of ethane over ethylene on low-cost hyper-crosslinked polymers

Aminal-Linked Covalent Organic Frameworks with hxl-a and Quasi-hcb Topologies for Efficient C2 H6 /C2 H4 Separation

In reticular chemistry, topology is a powerful concept for defining the structures of covalent organic frameworks (COFs). However, due to the lack of diversity in the symmetry and reaction stoichiometry of the monomers, only 5% of the two-dimensional topologies have been reported to be COFs. To overcome the limitations of COF connectivity and pursue novel topologies in COF structures, two aminal-linked COFs, KUF-2 and KUF-3, are prepared, with dumbbell-shaped secondary building units. Linear dialdehydes and piperazine are condensed at a ratio of 1:2 to construct an aminal linkage, leading to unreported hxl-a (KUF-2) and quasi-hcb (KUF-3) structures. Notably, KUF-3 displays top-tier C2 H6 /C2 H4 selectivity and C2 H6 uptake at 298 K, outperforming most porous organic materials. The intrinsic aromatic ring-rich and Lewis basic pore environments, and appropriate pore widths enable the selective adsorption of C2 H6 , as confirmed by Grand Canonical Monte Carlo simulations. Dynamic breakthrough curves revealed that C2 H6 can be selectively separated from a gas mixture of C2 H6 and C2 H4 . This study suggests that topology-based design of aminal-COFs is an effective strategy for expanding the field of reticular chemistry and provides the facile integration of strong Lewis basic sites for selective C2 H6 /C2 H4 separation.

Potential of hypercrosslinked microporous polymer based on carbazole networks for Pb(II) ions removal from aqueous solutions

In this research, porous adsorbents of hypercrosslinked microporous polymer based on carbazole networks (HCP-CN) were synthesized for Pb(II) elimination from wastewaters. The results demonstrated that the extreme HCP-CN adsorbents utilization in wastewater treatment could remove more than 99.88% of Pb (II) ions. Furthermore, the two consumed adsorbents similarly indicated rapid adsorption kinetics, and it merely took a while to achieve adsorption equilibrium. These characteristics showed that HCP-CN adsorbent was an outstanding candidate for Pb(II) elimination from wastewater. Besides, the thermodynamic characteristics involving Gibbs free energy change (∆G⁰), entropy change (∆S⁰), and enthalpy change (∆H⁰) of the adsorption procedure were evaluated, and the results affirmed that the adsorption process was exothermic and spontaneous. In addition, response surface methodology (RSM) as a statistical investigation was used to optimize adsorption factors to obtain maximum adsorption capacity and investigate the interactive effect of parameters using central composite design (CCD). Optimum conditions obtained by RSM for maximum adsorption capacity of 26.02 mg/g are 35 °C, 40 mg/L, 11, 60 min, and 99.88 for temperature, initial concentration, pH, time, and removal percent, respectively. In the kinetic modeling study, the second-order model was selected as the best model. The values R² at temperatures 35 °C, 40 °C, and 55 °C are 0.997, 0.9997, and 0.998, respectively. In the isotherm modeling, Hill model with a value R² of 0.9766 has a superior precision compared to the other isotherm models. Also, the values of ΔH and ΔS at Pb(II) concentration of 60 mg/L are 122.622 kJ/mol and 0.463 kJ/mole K, respectively.

Rational Construction and Performance Regulation of an In(III)-Tetraisophthalate Framework for One-Step Adsorption-Phase Purification of C2H4 from C2 Hydrocarbons

The development of porous materials for ethylene (C₂H₄) separation and purification, a very important separation process in the chemical industry, is urgently needed but quite challenging. In particular, the realization of selectivity-reversed adsorption (namely, C₂H₄ is not preferentially adsorbed) and the simultaneous capture of multinary coexisting impurities such as ethane (C₂H₆) and acetylene (C₂H₂) will significantly simplify process design and reduce energy and cost consumption, but such porous materials are quite difficult to design and have not yet been fully explored. In this work, by employing an aromatic-rich bithiophene-based tetraisophthalate ligand, we solvothermally fabricated an anionic In(III)-based framework termed ZJNU-115 featuring In(COO)₄ as an inorganic secondary building unit as well as one-dimensional channels. Due to the absence of unsaturated metallic sites, together with aromatic-rich channel surface decorated with abundant hydrogen-bonding acceptors of carboxylate oxygen and thiophene sulfur atoms, desolvated ZJNU-115 exhibited an unusual adsorption relationship with respect to C₂ hydrocarbons, namely, simultaneous and preferable capture of C₂H₆ and C₂H₂ over C₂H₄ at the temperatures investigated, thus representing a rare metal-organic framework (MOF) with the promising potential for one-step adsorption-phase purification of C₂H₄ from a trinary C₂ hydrocarbon mixture. Compared to a few of the MOFs reported for such an application, ZJNU-115 displayed simultaneously good adsorption selectivities of both C₂H₂ and C₂H₆ over C₂H₄. Furthermore, its separation potential can be postsynthetically tailored by substituting dimethylammonium (Me₂NH₂⁺) counterions with tetraalkyl ammonium ions (NR₄⁺; R = Me, Et, or n-Pr). More importantly, ZJNU-115 was stable in various organic solvents as well as aqueous solutions with pH values ranging from 5 to 9, thus laying a solid foundation for its practical applications. The design principle and the performance regulation strategy adopted in this work will offer valuable guidance for the contrapuntal construction of porous MOFs employed for direct multicomponent purification of C₂H₄ with improved performance.

An aromatic-rich cage-based MOF with inorganic chloride ions decorating the pore surface displaying the preferential adsorption of C2H2 and C2H6 over C2H4

An aromatic-rich chloride-embedded nanocage-based MOF displayed an unusual adsorption relationship towards C₂ hydrocarbons, with the potential for C₂H₄ separation and purification application.

Effects of Thiophene and Benzene Ring Accumulation on the Photocatalytic Performance of Polymers

Six polymers were prepared with 4,4',4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine as the amine unit, and six different aldehyde units as substrates. The effects of the number of thiophene and benzene rings on the degradation of tetracycline (TC) in water were studied using polymer photocatalysts, and the reaction mechanism was discussed. The results indicate that ThTA-3 containing three thiophene group monomers and BATA-1 with one benzene ring unit monomer have higher absorption and utilization of visible light. In addition, ThTA-3 and BATA-1 have stronger charge separation and transfer capabilities and better morphology and thermal stability.