Hydroxyl porous aromatic frameworks for efficient adsorption of organic micropollutants in water

Thermal and bisphenol-A adsorption properties of a zinc ferrite/β-cyclodextrin polymer nanocomposite

The present study investigated the use of a nanocomposite, produced by reinforcing nanosize zinc ferrite (ZnFe₂O₄) in a porous β-CD based polymeric matrix (β-CD-E-T/ZnFe₂O₄), for the removal of Bisphenol A (BPA) from aqueous solutions via adsorption. The thermal stability of the β-CD-based polymer and β-CD-E-T/ZnFe₂O₄ nanocomposite were investigated using simultaneous thermal analysis at four heating rates. Non-isothermal isoconversion methods were employed to study the thermal degradation kinetics of the β-CD based polymer before and after ZnFe₂O₄ nano-filling. The results showed that ZnFe₂O₄ nano-reinforcement increased the activation energy barrier for the thermal degradation of the β-CD-based polymeric matrix. Adsorption experiments showed that the β-CD-E-T/ZnFe₂O₄ nanocomposite exhibited very high BPA adsorption within 5 minutes. Isotherm, kinetics, and thermodynamic investigations revealed that the adsorption of BPA was via multilayer adsorption on a heterogeneous β-CD-E-T/ZnFe₂O₄ surface. The thermodynamic studies indicated that BPA adsorption on β-CD-E-T/ZnFe₂O₄ was spontaneous and exothermic. Overall, the β-CD-E-T/ZnFe₂O₄ nanocomposite showed less thermal degradation and high efficiency for removing BPA from contaminated water, indicating its potential as a promising material for wastewater treatment applications.

Design of hydroxyl-functionalized nanoporous organic polymer with tunable hydrophilic-hydrophobic surface for solid phase extraction of neonicotinoid insecticides

As being widely used insecticides, neonicotinoid residues are toxic and harmful to human health and aquatic ecosystems. Thus, the sensitive monitoring of neonicotinoids in water and food samples is highly desirable to reduce their risks to humans. Herein, four novel hydroxyl-functionalized nanoporous organic frameworks (OH-NOP1, OH-NOP2, OH-NOP3 and OH-NOP4) with tunable hydrophilic-hydrophobic surface have been designed and fabricated for the first time by employing luteolin as monomer and 4,4'-bis(chloromethyl)-1,1'-biphenyl as crosslinker at the molar ratio of 3:1, 1:1, 1:3 and 1:6, respectively. When the molar ratio of luteolin to crosslinker was 1:3, OH-NOP3 was obtained and it presented the highest affinity with excellent adsorption performance towards the studied neonicotinoids. The adsorption mechanism was proposed to be the strong hydrogen bond, polar interaction, Lewis acid-base interaction and pore adsorption between OH-NOP3 and neonicotinoids. Then, utilizing OH-NOP3 as sorbent for solid phase extraction cartridges, an effective method for extraction and preconcentration of neonicotinoids followed by high performance liquid chromatography analysis has been developed for quantitative detection of neonicotinoids from water and edible fungi. The method provided good linearity over the range of 0.06-100.0 ng mL^-1 for lake water, 1.5-100.0 ng g^-1 for pleurotus eryngii and sea-shroom. Low detection limit (at the signal to noise ratio of 3) was achieved in the range of 0.02-0.08 ng mL^-1 for water, 0.50-0.60 ng g^-1 for pleurotus eryngii and 0.50-0.80 ng g^-1 for sea-shroom, while the limit of quantification was 0.06-0.25 ng mL^-1, 1.50-1.80 ng g^-1 and 1.50-2.50 ng g^-1, respectively. Satisfactory method recoveries (85.1-112%) were obtained, with relative standard deviations below 8.2%. This study offered a new strategy for designing efficient sorbents to adsorb or remove organic pollutants based on the structure and properties of substrates.

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar-Powered Volatile Organic Compounds Management

Freshwater shortage is becoming one of the most critical global challenges owing to severe water pollution caused by micropollutants and volatile organic compounds (VOCs). However, current purification technology shows slow adsorption of micropollutants and requires an energy-intensive process for VOCs removal from water. In this study, a highly efficient molecularly engineered covalent triazine framework (CTF) for rapid adsorption of micropollutants and VOC-intercepting performance using solar distillation is reported. Supramolecular design and mild oxidation of CTFs (CTF-OXs) enable hydrophilic internal channels and improve molecular sieving of micropollutants. CTF-OX shows rapid removal efficiency of micropollutants (>99.9% in 10 s) and can be regenerated several times without performance loss. Uptake rates of selected micropollutants are high, with initial pollutant uptake rates of 21.9 g mg^-1  min^-1 , which are the highest rates recorded for bisphenol A (BPA) adsorption. Additionally, photothermal composite membrane fabrication using CTF-OX exhibits high VOC rejection rate (up to 98%) under 1 sun irradiation (1 kW m^-2 ). A prototype of synergistic purification system composed of adsorption and solar-driven membrane can efficiently remove over 99.9% of mixed phenol derivatives. This study provides an effective strategy for rapid removal of micropollutants and high VOC rejection via solar-driven evaporation process.

Porous aromatic frameworks with high Pd nanoparticles loading as efficient catalysts for the Suzuki coupling reaction

The development of efficient and recyclable heterogeneous Pd catalysts is an area of continuing attention due to their critical applications in organic synthesis and pharmaceutical production. In this study, two novel heterogeneous catalysts Pd@PAF-182 and Pd@PAF-183 were prepared by the immobilization/NaBH₄ reduction of PdCl₄^2- on hydrophilic cationic porous aromatic frameworks (PAF-182 and PAF-183), which were synthesized via a Yamamoto-type Ullmann coupling reaction from the corresponding aryl quaternary phosphonium salt monomer. Characterization by powder X-ray diffraction (PXRD), solid-state Cross-Polarization Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) established the structures of the as-prepared catalysts. Inductively coupled plasma atomic emission spectrometry (ICP-AES) detection showed that the loading of Pd nanoparticles (Pd NPs) were 29.4 wt% for Pd@PAF-182 and 37.5 wt% for Pd@PAF-183, much higher than those of similar porous materials. Evaluation of the catalytic activity of the Pd@PAFs using Suzuki coupling as the model reaction demonstrated that as little as 0.12 mol% of Pd NPs could catalyze the Suzuki coupling with high efficiency, achieving yields up to 99% at 80 °C in 8 h. Recycling experiments also suggested that Pd@PAF-182 and Pd@PAF-183 maintained high catalytic activity with negligible leaching of Pd NPs after five cycles.

Thiol/methylthio-functionalized porous aromatic frameworks for simultaneous capture of aromatic pollutants and Hg(II) from water

Simultaneously capturing organic pollutants and heavy metal can greatly reduce the water remediation time and cost, however it is still a great challenge presently. Herein, two novel thiol/methylthio-functionalized porous aromatic frameworks were synthesized as sorbents via the Sonogashira-Hagihara reaction of 1,3,5-triethynylbenzene and 1,3,5-tris(4-bromophenyl) benzene, the subsequent chloromethylation of the phenyl rings, and the final nucleophile substitution of -Cl groups by NaSH/NaSMe. These two sorbents were characterized by FT-IR spectra, energy dispersive X-ray spectra, scanning electron microscope, nitrogen adsorption analysis, thermo-gravimetric analysis, and elemental analyses. Adsorption experiments displayed that new sorbents had high uptake abilities and fast adsorption kinetics for aromatic pollutants and mercury (II) (Hg(II)). The maximum adsorption capacity (Q_max) of toluene and m-xylene on both new sorbents were 531.9-571.4 mg/g with the kinetic binding rate constants (k_obs) of 0.00276-0.02422 g/mg/min, and the Q_max values of Hg(II) were 148.1-180.3 mg/g with k_obs of 0.00592-0.01573 g/mg/min. Moreover, new sorbents indicated high simultaneous uptake abilities for these pollutants with good reusability, and finally they were successfully applied to the simultaneous remediation of these pollutants in two simulated sewages with high and low concentration, indicating their great practical application potential in wastewater remediation.

Porous Organic Polymer Synthesized by Green Diazo-Coupling Reaction for Adsorptive Removal of Methylene Blue

A porous organic polymer (marked as DT-POP), which contains abundant free phenolic hydroxyl groups, is synthesized by the well-known green azo-coupling reaction in water, characterized, and utilized as an effective adsorbent for the elimination of methylene blue (MB) from water solutions. The presence of permanent mesopores, abundant active functional groups, and π-electron enrichment ascribed to phenyl rings make DT-POP an efficient adsorbent for MB due to strong hydrogen bonding, π-π, and electrostatic interactions with the cationic dye MB. DT-POP with high stability and high adsorption capacity can be reused many times and thus shows high applicability in pollutant disposal.