Self-Reducible Conjugated Microporous Polyaniline for Long-Term Selective Cr(VI) Detoxication Driven by Tunable Pore Dimension

High Catalytic Selectivity of Electron/Proton Dual-Conductive Sulfonated Polyaniline Micropore Encased IrO2 Electrocatalyst by Screening Effect for Oxygen Evolution of Seawater Electrolysis

Acidic seawater electrolysis offers significant advantages in high efficiency and sustainable hydrogen production. However, in situ electrolysis of acidic seawater remains a challenge. Herein, a stable and efficient catalyst (SPTTPAB/IrO2) is developed by coating iridium oxide (IrO2) with a microporous conjugated organic framework functionalized with sulfonate groups (-SO3H) to tackle these challenges. The SPTTPAB/IrO2 presents a -SO3H concentration of 5.62 × 10-4 mol g-1 and micropore below 2 nm numbering 1.026 × 1016 g-1. Molecular dynamics simulations demonstrate that the conjugated organic framework blocked 98.62% of Cl- in seawater from reaching the catalyst. This structure combines electron conductivity from the organic framework and proton conductivity from -SO3H, weakens the Cl- adsorption, and suppresses metal-chlorine coupling, thus enhancing the catalytic activity and selectivity. As a result, the overpotential for the oxygen evolution reaction (OER) is only 283 mV@10 mA cm-2, with a Tafel slope of 16.33 mV dec-1, which reduces 13.8% and 37.8% compared to commercial IrO2, respectively. Impressively, SPTTPAB/IrO2 exhibits outstanding seawater electrolysis performance, with a 35.3% improvement over IrO2 to 69 mA cm-2@1.9 V, while the degradation rate (0.018 mA h-1) is only 24.6% of IrO2. This study offers an innovative solution for designing high-performance seawater electrolysis electrocatalysts.

Site Energy Distribution Coupled with Statistical Physics Modeling for Cr(VI) Adsorption onto Coordination Polymer Gel

In this work, a novel pristine coordination polymer gel composed of zirconium and 2-amino-5-mercapto-1,3,4-thiadiazole is unveiled and explored to remove Cr(VI) from aqueous systems. A Box-Behnken design, coupled with a genetic algorithm and desirability function, was used for optimizing the controllable factors for maximum removal efficiency. Under optimized conditions (A = 50 mg L-1, B = 40 mg, C = 90 min, and D = 4), 99% of Cr(VI) was removed, and the saturation adsorption capacity recorded was 132.37 mg g-1. The adsorption data were investigated through statistical physics modeling. The most suited statistical physics model (monolayer with three energies; R2 = 0.994-0.997, χ2 = 0.008-0.024), combined with site energy distribution analysis, XPS, and FTIR, unraveled the uptake mechanism. At the first and third active sites, Cr(VI) uptake was multimolecular (n > 1), while at the second active site, it was a mixed multimolecular (298 K, n > 1) and multidocking (308 and 318 K, n < 1). The adsorption energy values indicated the involvement of coordination exchange (E1 = 53.40-58.47 kJ mol-1), electrostatic interaction (E2 = 29.56-32.29 kJ mol-1), and hydrogen bonding (E3 = 24.68-28.35 kJ mol-1) in Cr(VI) adsorption. The BSf(1.5, α) model fitted best (R2 = 0.976-0.994, χ2 = 0.023-0.377) to the kinetic data under all conditions. Common coexisting ions had no significant impact on removal efficiency (%R > 97% at 1:3), and the sorbent could be reutilized up to 5 uptake-elution cycles (>96% efficiency). The practical utility of ZrAMTD was investigated by remediating Cr(VI) contaminated real water samples (%R ≥ 92.91%).

Powders to Thin Films: Advances in Conjugated Microporous Polymer Chemical Sensors

Chemical sensing of harmful species released either from natural or anthropogenic activities is critical to ensuring human safety and health. Over the last decade, conjugated microporous polymers (CMPs) have been proven to be potential sensor materials with the possibility of realizing sensing devices for practical applications. CMPs found to be unique among other porous materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) due to their high chemical/thermal stability, high surface area, microporosity, efficient host-guest interactions with the analyte, efficient exciton migration along the π-conjugated chains, and tailorable structure to target specific analytes. Several CMP-based optical, electrochemical, colorimetric, and ratiometric sensors with excellent selectivity and sensing performance were reported. This review comprehensively discusses the advances in CMP chemical sensors (powders and thin films) in the detection of nitroaromatic explosives, chemical warfare agents, anions, metal ions, biomolecules, iodine, and volatile organic compounds (VOCs), with simultaneous delineation of design strategy principles guiding the selectivity and sensitivity of CMP. Preceding this, various photophysical mechanisms responsible for chemical sensing are discussed in detail for convenience. Finally, future challenges to be addressed in the field of CMP chemical sensors are discussed.

Fine-Tuning Electron-Donor Capability in the Basic Anion of Poly(ionic liquid) Frameworks for Revolutionizing Catalytic Synthesis of Ethyl Methyl Carbonate with Both Ultrahigh Catalytic Activity and Selectivity

Ethyl methyl carbonate (EMC) is a crucial solvent extensively utilized in lithium-ion battery electrolytes; the transesterification of dimethyl carbonate (DMC) with ethanol is a pivotal reaction for EMC production. However, this reaction faces challenges due to the trade-off between catalytic activity and selectivity from the basic catalysts. In this issue, we report an innovative strategy through fine-tuning the electron-donor capability of the basic phenolate anion ([PhO]) in a novel poly(ionic liquid) (PIL) framework, as synthesized via an alkylation reaction between 1,3,5-tris(bromomethyl)benzene, biphenyldiimidazole, and N,N'-carbonyldiimidazole (CDI) to trigger targeted basicity that can directionally catalyze the transesterification of DMC with ethanol, so as to achieve both ultrahigh catalytic activity and selectivity toward EMC. By varying the substituent groups with electron-withdrawing and electron-donating effects on the phenolate anion, the PILs show expected changes in the catalytic performance, following well with the trend of charge density on these substituted phenolate anions. The optimized catalyst [CPIL-CDI][MeOPhO], induced by p-methoxyphenolate anions, allows an extraordinary EMC yield of 72.19% and an EMC selectivity of 91.48% under mild conditions without any process intensifications, suppressing all of the reported catalysts reported to date. Outcomes and approaches shown in this work have the potential to expedite the systematic design of cations and anions within PILs for industrial-scale EMC production through environmentally friendly transesterification processes.

Self-Healing Conjugated Microporous Polyanilines for Effective and Continuous Catalytic Detoxification of 4-Nitrophenol to 4-Aminophenol

Detoxification of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with high efficiency and dynamic performance is challenging for a polymeric catalyst. Herein, a series of conjugated microporous polyanilines (CMPAs), capable of efficiently catalytically reducing 4-NP, were synthesized based on the Buchwald-Hartwig cross-coupling reaction mechanism. By adjusting the types of linkers and the molar ratios of linker to core, CMPAs with different Brunauer-Emmett-Teller (BET) specific surface areas and reduction degrees were obtained and used as the catalysts in reducing 4-NP. The ultrahigh catalytic reduction efficiency (K = 141.32 s-1 g-1, kapp = 0.00353 s-1) was achieved when using CMPA-3-0.7 as the catalyst (prepared with 4,4'-diaminodiphenylamine as the linker and a 0.7:1 molar ratio of linker to core). The catalytic reduction performance exhibited a strong correlation with the reduction degree and BET specific surface area of CMPAs. Furthermore, they also exhibit excellent cycling stability and dynamic performance. The coexistence of a microporous structure and high BET specific surface area endowed CMPAs with an increased number of catalytic active centers. The reversible redox transformation of CMPAs in the presence of NaBH4 and air enabled self-healing (the oxidation units in CMPAs were reduced to reduction units by NaBH4, and the newly generated reduction unit in CMPAs was subsequently oxidized to its original state by the O2 in the air), leading to the reduction reaction of 4-NP proceeded continuously and stably. The aforementioned factors resulted in the high efficiency of CMPAs for reducing 4-NP to 4-AP, enhancing the practical application prospects of CMPAs in the detoxification of 4-NP wastewater.

Conjugated Microporous Poly(aniline) Enabled Hierarchical Porous Carbons for Hg(II) Adsorption

Hierarchical porous carbons equipped with heteroatoms and diffusion pores have a wide application prospect in adsorption. Herein, we report N-autodoped porous carbons (PTPACs), which were derived from rigid N-rich conjugated microporous poly(aniline)s (CMPAs) and show their all-around applicability in heavy metal adsorption. Their molecular structure could be delicately tuned from 3D organic networks to graphitic carbons through simply adjusting the pyrolysis temperature, affording unique hybrid features of hierarchical micro-meso-macroporosity and amount-tunable nitrogen defects, as validated by the enhanced CO₂ adsorption capacities reaching 5.0 mmol g^-1, a 230% increase compared to the precursor (2.15 mmol g^-1). They therefore show promising a Langmuir adsorption capacity of 434.8 mg g^-1 toward mercury ions, which could be rapidly achieved within a short 20 min. Based on the comprehensive experimental, characterization, and DFT calculation studies, we rationally reveal these impressive adsorptions arise from the hybrid function of chemisorption contributed by populated nitrogen defects and physical adsorption achieved by synergistic functions in the diffusion and storage pores. Outcomes mark the high merits of PTPACs in addressing recent global challenges in environmental engineering.

Highly efficient poly(6-acryloylamino-N-hydroxyhexanamide) resin for adsorption of heavy metal ions

Heavy metal wastewater pollution has become an ecological challenge worldwide. This study reports the development of a novel poly (6-acryloylamino-N-hydroxyhexanamide) (PAHHA) resin for effective adsorption of heavy metal ions, including Cu²⁺, Pb²⁺ and Ni²⁺. The chelating resin was synthesized by the grafting reaction between 6-amino-N-hydroxyhexanamide and polyacrylic resin, thus containing the hydroxamate and acylamino groups. The batch adsorption experiments revealed that the PAHHA resin exhibited an excellent adsorption performance for Cu²⁺, Pb²⁺ and Ni²⁺. The maximum adsorption capacities of Cu²⁺, Pb²⁺ and Ni²⁺ were determined to be 238.59, 232.48 and 115.77 mg·g^-1, respectively. Based on the adsorption kinetics, the pseudo-second-order kinetic model was noted to fit well for all metal ions. The metal ion concentration as a function of the equilibrium adsorption capacity fitted well with the Langmuir isotherm, thus indicating the single layer adsorption process. The adsorption mechanism was investigated by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS) and adsorption isotherms. It was revealed that the PAHHA resin possessed multiple active sites, including -CONHOH, -CONH- and -COOH, which could strongly adsorb the metal ions. Specifically, the -CONHOH group displayed a high affinity by forming a stable five-membered ring with heavy metal ions. Overall, the developed resin exhibits advantages such as simple synthesis, inexpensive raw material and good recyclability, along with high adsorption ability, thus providing a new approach for efficiently treating wastewater contaminated with heavy metal ions.

Simultaneous Separation and Recovery of Gold and Copper from Electronic Waste Enabled by an Asymmetric Electrochemical System

Exploiting efficient strategies for the selective separation and extraction of valuable metals from e-waste is in urgent demand to offset the ever-increasing depletion of metal resources, satisfy the sustainable supply of metal resources, and reduce the environmental impact from toxic metals. Herein, an asymmetric electrochemical system, constructed by polyaniline (PANI) nanofibers grown on carbon cloth (CC) and CC as the respective counter and working electrodes, is presented for the simultaneous and selective extraction of gold and copper from e-waste leachate solution. Harnessing the established CC/PANI//CC system, CC/PANI as the anode electrode is capable of selectively and rapidly extracting gold with high efficiency, accompanied by excellent reusability. Meanwhile, cathodic CC electrode is found to achieve almost 100% recovery of copper at a voltage of -1.2 V. Furthermore, the feasibility of the proposed asymmetric electrochemical system is further exemplified in waste central processing unit (CPU) leaching solution, enabling to recover simultaneously gold and copper with high purity. This work will provide meaningful guidance for simultaneous separation and recovery of multiple valuable metals from real e-waste.

Porosity Design on Conjugated Microporous Poly(Aniline)S for Exceptional Mercury(II) Removal

The use of conjugated microporous polymers (CMPs) in practical wastewater treatment demands further design on the pore structure, otherwise their adsorption capacities toward heavy-metal ions were moderate. Here, we report a rational design approach, which produces hybrid molecular pores in conjugated microporous poly(aniline)s (CMPAs) for mercury removal. It is achieved through a delicate interval introduction of linkers with differential molecular lengths during polymerization, acquiring both diffusion channels and storage pores for radical enhancement of mass transfer and adsorption storage. The resulting CMPA-M featured a large adsorption capacity of 975 mg g^-1 and rapid kinetics that could remove 94.8% of 50 mg g^-1 of mercury(II) within a very short contact time of 48 s, with a promising initial adsorption rate h as high as 113 mg g^-1 min^-1, which was 2.54-fold larger in the adsorption capacity and 45.2-fold faster in the adsorption efficiency compared with the undeveloped CMPAs. More importantly, our CMPA-M-2, with robust stability and easy reusability, was able to scavenge over 99.9% of mercury(II) from the actual wastewater in a harsh condition with a very low pH of 0.77, extremely high salinity of 53,157 mg L^-1, and complex impurities, featuring exceptional selectivity that allows us to extract and recycle a high purity of 99.1% of mercury from the wastewater. These outcomes demonstrate the unprecedented potential of CMPs for environmental remediation and real-world mercury extraction and present benchmarks for CMP-based mercury adsorbents.

Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI).