Functional Porous Organic Polymers with Conjugated Triaryl Triazine as the Core for Superfast Adsorption Removal of Organic Dyes

Hybrid Dendrimer Network based on Silsesquioxane and Glycidyl Methacrylate for Enhanced Adsorption of Iodine and Dyes in Environmental Remediation

A novel hybrid network was synthesized in two steps: the first step involved the attachment of glycidyl methacrylate (GMA) to octa(aminophenyl) silsesquioxane (OAPS) through a ring-opening reaction, forming a hybrid dendrimer structure, and the second step involved the cross-linking of hybrid dendrimer using an azobisisobutyronitrile initiator to create the final hybrid network of OAPS-GMA. The synthesized hybrid material was comprehensively characterized using fourier transform infrared Spectroscopy (FTIR), nuclear magnetic resonance ((1H, 13C, and 29Si NMR) spectroscopy, thermogravimetric Analysis (TGA), and scanning electron microscopy (SEM). The BET surface area was found to be 25.44 m2/g, and significant 2.341 cm3/g of total pore volume was observed. The TGA analysis shows that the material is highly stable up to 450 °C. The synthesized network demonstrated remarkable adsorption capacities for iodine and dyes. It exhibited an iodine adsorption capacity of 3.4 g/g from vapors and 874 mg/g from solution. Additionally, it showed significant adsorption capacities for Rhodamine B and Congo red, with values of 762 mg/g and 517 mg/g, respectively. This study not only provides a novel method for preparing GMA-functionalized silsesquioxane-based porous hybrid polymers but also contributes to advancing solutions for environmental pollution issues.

Solid-State Fluorescent Organic Polymers for Visual Detection and Elimination of Heavy Metals in Water

Selective sensing and removal of toxic heavy metals from water are highly essential since their presence poses significant health and environmental hazards. Herein, we designed and synthesized a novel fluorescent nonconjugated organic polymer by strategically incorporating two key functional groups, namely, a dansyl fluorophore and dithiocarbamate (DTC). Different characterization techniques, including 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR), and fluorescence spectroscopy, were performed to understand its structure and material properties. The quantum yield of 4.72% and its solid-state fluorescence indicate that it has potential for various applications in several technological and scientific domains. In this study, we investigated a specific application involving the detection and elimination of heavy metals from water. Interestingly, the presence of dansyl and DTC moieties demonstrated remarkable selectivity toward Cu2+, Co2+, Ni2+, Fe3+, and Fe2+ sensing, displaying distinct color changes specific to each metal. Cu2+ resulted in a yellow color, Co2+ showed a green color, Ni2+ displayed a pale yellowish-green color, and Fe2+/Fe3+ exhibited a brown color. The LOD (limit of detection) for each metal was obtained in the nanomolar range by using a fluorescence spectrometer and the micromolar range from UV-visible spectra: 13.27 nM and 0.518 μM for Cu2+, 8.27 nM and 0.581 μM for Co2+, 14.36 nM and 0.140 μM for Ni2+, 14.95 nM and 0.174 μM for Fe2+, and 15.54 nM and 0.33 μM for Fe3+. Moreover, the DTC functionality on its backbone facilitates effective interaction with the aforementioned heavy metals, subsequently removing them from water (except Fe2+ and Fe3+), validating its dual functionality as both an indicator and a purifier for heavy metals in water. The polymer exhibited a maximum adsorption capacity of 192.30 mg/g for Cu2+, 159.74 mg/g for Co2+, and 181.81 mg/g for Ni2+. Furthermore, this approach exhibits versatility in crafting fluorescent polymers with adjustable attributes that are suitable for a wide range of applications.

Triazine-based conjugated polymers with regulation of D-A configuration for enhanced photocatalytic activity

Photocatalysis is a green and environmentally friendly method for degrading dangerous and nonbiodegradable pollutants. In this study, a sequence of metal-free triazine-based electronic donor-acceptor (D-A) conjugated polymers Tr-X (X = Th, BT, BTh) were prepared by D-A configuration regulation between triazine (Tr) and monomers containing N and S, such as thiophene (Th), bithiophene (BTh) and benzothiadiazole (BT) units, for the photocatalytic degradation of bisphenol A (BPA) and benzene contaminants in water under visible light. Among these, Tr-BTh exhibited complete photocatalytic degradation owing to its excellent D-A configuration. Moreover, the N and S atoms, which are rich in triazine and thiophene units, serve as highly dispersed reactive sites. The separation and transfer of photogenerated carriers can be further improved by expanding the light-absorption range of polymers. In addition, the polymers showed good adsorption for BPA and other aromatic organic pollutants through π-π interaction and surface hydrogen bonding, which provides a facile strategy for efficient polymer-based photocatalysts for water purification.

Facile Fabrication of Porous Adsorbent with Multiple Amine Groups for Efficient and Selective Removal of Amaranth and Tartrazine Dyes from Water

The development of an advanced dye adsorbent that possesses a range of beneficial characteristics, such as high adsorption capacity, swift adsorption kinetics, selective adsorption capability, and robust reusability, remains a challenge. This study introduces a facile method for fabricating an amine-rich porous adsorbent (ARPA), which is specifically engineered for the adsorptive removal of anionic dyes from aqueous solutions. Through a comprehensive assessment, we have evaluated the adsorption performance of ARPA using two benchmark dyes: amaranth (ART) and tartrazine (TTZ). Our findings indicate that the adsorption process reaches equilibrium in a remarkably short timeframe of just 20 min, and it exhibits an excellent correlation with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, ARPA has demonstrated an exceptional maximum adsorption capacity, with values of 675.68 mg g-1 for ART and 534.76 mg g-1 for TTZ. In addition to its high adsorption capacity, ARPA has also shown remarkable selectivity, as evidenced by its ability to selectively adsorb TTZ from a mixed dye solution, a feature that is highly desirable for practical applications. Beyond its impressive adsorption capabilities, ARPA can be efficiently regenerated and recycled. It maintains a high level of original removal efficiency for both ART (76.8%) and TTZ (78.9%) even after five consecutive cycles of adsorption and desorption. Considering the simplicity of its synthesis and its outstanding adsorption performance, ARPA emerges as a highly promising material for use in dye removal applications. Consequently, this paper presents a straightforward and feasible method for the production of an effective dye adsorbent for environmental remediation.

Nanofibrous Porous Organic Polymers and Their Derivatives: From Synthesis to Applications

Engineering porous organic polymers (POPs) into 1D morphology holds significant promise for diverse applications due to their exceptional processability and increased surface contact for enhanced interactions with guest molecules. This article reviews the latest developments in nanofibrous POPs and their derivatives, encompassing porous organic polymer nanofibers, their composites, and POPs-derived carbon nanofibers. The review delves into the design and fabrication strategies, elucidates the formation mechanisms, explores their functional attributes, and highlights promising applications. The first section systematically outlines two primary fabrication approaches of nanofibrous POPs, i.e., direct bulk synthesis and electrospinning technology. Both routes are discussed and compared in terms of template utilization and post-treatments. Next, performance of nanofibrous POPs and their derivatives are reviewed for applications including water treatment, water/oil separation, gas adsorption, energy storage, heterogeneous catalysis, microwave absorption, and biomedical systems. Finally, highlighting existent challenges and offering future prospects of nanofibrous POPs and their derivatives are concluded.

Porous Fe-Porphyrin as an Efficient Adsorbent for the Removal of Ciprofloxacin from Water

Antibiotics are widely used in medicine, but they are not fully metabolized in the body and can end up in wastewater. Conventional wastewater treatment methods fail to completely remove antibiotic residues, which can then enter rivers and streams. Adsorption is a promising technique for removing antibiotics from wastewater, even at low concentrations. The successful one-pot synthesis of an adsorbent, iron-containing porphyrin-based porous organic polymer (Fe-POP), was achieved through the reaction of pyrrole groups and terephthalaldehyde in the presence of FeCl3. Characterized by a substantial BET surface area of 597 m2 g-1, Fe-POP was systematically investigated for its adsorption potential in the removal of the antibiotic Ciprofloxacin (CIP) from aqueous solutions. By systematic variation of key parameters, including pH, adsorbent loading, and CIP concentration, the adsorption conditions were optimized. Under the optimal conditions at pH = 3, CIP concentration of 5 ppm, and 25 mg of Fe-POP, the maximum adsorption capacity reached an impressive 263 mg g-1. The robust adsorption behavior was elucidated through the fitting of experimental data to the Langmuir adsorption isotherm (R2 = 0.962) and the pseudo-second-order kinetic model (R2 = 0.999) with lower error values. These models suggested that the adsorption process predominantly involved chemical interactions between CIP molecules and the Fe-POP surface. Fe-POP exhibited a robust structure with a high adsorption capacity, showcasing its efficacy in removing CIP contaminants from water. Therefore, Fe-POP can be considered a valuable adsorbent for water treatment applications, specifically for antibiotic removal.

Photostimulus-Responsive Peptide Dot-Centered Covalent Organic Polymers: Effective Pesticide Sensing via Enhancing Accessibility

Pesticide detection and monitoring are necessary for human health as the overapplication has serious consequences for environmental pollution. Herein, a proper modulation strategy was implemented to construct the photostimulus-responsive peptide-dot-centered covalent organic polymer (P-PCOP) nanoarchitecture for selective sensing of pesticides. The as-constructed P-PCOP was prepared at room temperature by using amino-containing peptide dots as a building block instead of common organic molecules, and the merits of P-PCOP enable it to reduce the steric hindrance of recognition, enhance the interfacial contact of the target, and facilitate the accessibility of sites, which promises to improve the sensitivity. The P-PCOF exhibited a low detection limit of 0.38 μg L-1 to cartap over the range of 1-80 μg L-1 (R2 = 0.9845), and the recoveries percentage in real samples was estimated to be 93.39-105.82%. More importantly, the DFT calculation confirmed the selective recognition ability of P-PCOP on chemical pesticides. In conjunction with a smartphone-integrated portable reading device, on-site chemical sensing is achieved. The proper modulation strategy of fixing a functional guest on the COP system contributes to the advanced structure-chemical properties that are conducive to their applications in chemical sensing.

Construction of magnetic hydroxyl group-enriched hyper cross-linked polymers with functional triazine as the core for efficient enrichment of plant growth regulators

The determination of trace plant growth regulators (PGRs) residues in water and food samples make it crucial to develop novel sample pretreatment methods for the enrichment of PGRs. Herein, a novel magnetic hyper cross-linked polymer (M-CTT-9OH-HCP) was constructed and served as a magnetic adsorbent for the efficient extraction of some PGRs from water, watermelon, tomatoes, and milk samples for the first time. Combined with high performance liquid chromatography-fluorescence detection (HPLC-FLD), the established method presented a good linearity (0.03-60.0 ng g-1 (ng mL-1), (r) ≥ 0.9973), satisfactory accuracy with method recoveries (83.0%-119%) and acceptable precision with the intra-day and inter-day variations (expressed as the relative standard deviations (RSDs) ≤ 9.8%). The limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 0.01-1.50 and 0.03-5.00 ng g-1/ ng mL-1. The results show that the established method is sensitive and efficient for the determination of PGRs in real samples.

Azo-Linked Porous Polycalix[n]arenes for the Efficient Removal of Organic Micropollutants from Water

Developing novel porous adsorbents for efficient wastewater treatment is significant to the environment protection. Herein, three porous polycalix[n]arenes (n = 4, 6, and 8) which had varying cavity sizes of the macrocycle (Azo-CX4P, Azo-CX6P, and Azo-CX8P) were prepared under mild conditions and tested for their potential application in water purification. Azo-CX8P with a larger cavity size of the macrocycle outperformed Azo-CX4P and Azo-CX6P in screening studies involving a range of organic micropollutants. It was proved that Azo-CX8P was especially efficient in the removal of cationic dyes because of its high negative surface charge. In terms of the adsorption of Rhodamine B with Azo-CX8P, the pseudo-second-order rate constant reaches 5.025 g·mg-1·min-1 with the maximum adsorption capacity being 1345 mg·g-1. These values are significantly higher compared with those recorded for most adsorbents. In addition, the easily prepared Azo-CX8P can be reused at least six times without a loss of the adsorption efficiency, demonstrating its potential use in water purification.

Removal of bromophenol blue from polluted water using a novel azo-functionalized magnetic nano-adsorbent

Water pollution from organic dyes poses a serious danger to the environment. In the present work, we report a novel adsorbent (ADFS) based on azo-dye-functionalized superparamagnetic iron oxide nanoparticles (SPIONs) for the removal of the anionic dye bromophenol blue (BPB) from contaminated water. The fabricated SPIONs, azo dye, and ADFS adsorbent were characterized with FTIR and UV-vis absorption spectroscopy, 1HNMR spectroscopy, mass spectrometry, SEM imaging, dynamic light scattering (DLS), zeta potential measurements, vibrating sample magnetometry, thermogravimetric analysis, differential thermal analysis, and X-ray diffraction analysis. DLS measurements showed a particle size of 46.1 and 176.5 nm for the SPIONs and the ADFS, respectively. The adsorbent exhibited an adsorption capacity of 7.43 mg g-1 and followed the pseudo-second-order kinetics model (r2 = 0.9981). The ADFS could efficiently remove BPB from water after stirring for 120 minutes at room temperature and pH 2. The adsorption process was proved to occur via physisorption, as revealed by the Freundlich isotherm (n = 1.82 and KF = 11.5). Thermodynamic studies implied that the adsorption is spontaneous (-8.03 ≤ ΔG ≤ -0.58 kJ mol-1) and enthalpy-driven might take place via van der Waals interactions and/or hydrogen bonding (ΔH = -82.19 kJ mol-1 and ΔS = -0.24 kJ mol-1 K-1).

Synthesis of two-dimensional triazine covalent organic frameworks at ambient conditions to detect and remove water pollutants

Synthesis of fully triazine frameworks (C3N3) by metal catalyzed reactions at high temperatures results in carbonized and less-defined structures. Moreover, metal impurities affect the physicochemical, optical and electrical properties of the synthesized frameworks, dramatically. In this work, two-dimensional C3N3 (2DC3N3) has been synthesized by in situ catalyst-free copolymerization of sodium cyanide and cyanuric chloride, as cheap and commercially available precursors, at ambient conditions on gram scale. Reaction between sodium cyanide and cyanuric chloride resulted in electron-poor polyfunctional intermediates, which converted to 2DC3N3 with several hundred micrometers lateral size at ambient conditions upon [2 + 2+2] cyclotrimerization. 2DC3N3 sheets, in bulk and individually, showed strong fluorescence with 63% quantum yield and sensitive to small objects such as dyes and metal ions. The sensitivity of 2DC3N3 emission to foreign objects was used to detect low concentration of water impurities. Due to the high negative surface charge (-37.7 mV) and dispersion in aqueous solutions, they demonstrated a high potential to remove positively charged dyes from water, exemplified by excellent removal efficiency (>99%) for methylene blue. Taking advantage of the straightforward production and strong interactions with dyes and metal ions, 2DC3N3 was integrated in filters and used for the fast detection and efficient removal of water impurities.

Treating waste with waste: Adsorption of anionic dyes in wastewater with surfactant-modified phosphogypsum

Phosphogypsum (PG) is a solid waste generated during the wet process of phosphoric acid production. The environmental-friendly disposal and recycling of PG is vital in the field of environmental solid waste treatment. In this study, PG is used for adsorbent of dyes in wastewater to achieve the goal of recycling waste with waste. Surfactant-modified phosphogypsum (ODBAC@PG) was prepared using octadecyl dimethyl benzyl ammonium chloride (ODBAC) as modifier. ODBAC@PG exhibits high adsorption capability for anionic dyes (methyl blue (MeB) and indocyanine carmine (IC)). The pseudo-second-order kinetic model fits the kinetic experimental data for the adsorption of two organic anionic dyes. Langmuir adsorption isotherm fits the adsorption characteristics of MeB and IC on ODBAC@PG, exhibiting a monolayer adsorption pattern. Thermodynamic parameters indicate the spontaneous and exothermic properties of MeB and IC on ODBAC@PG. MeB and IC have antagonistic effects on each other in binary adsorption system. High adsorption capacity after six cycles of experiments demonstrates the high reusability of ODBAC@PG. The nature for the adsorption includes electrostatic interaction, hydrogen bond and hydrophobic interaction. Using ODBAC@PG for dyes wastewater treatment can accomplish the goal of treating waste with waste and turning waste into treasure.

Porous organic polymers (POPs) for environmental remediation

Modern global industrialization along with the ever-increasing growth of the population has resulted in continuous enhancement in the discharge and accumulation of various toxic and hazardous chemicals in the environment. These harmful pollutants, including toxic gases, inorganic heavy metal ions, anthropogenic waste, persistent organic pollutants, toxic dyes, pharmaceuticals, volatile organic compounds, etc., are destroying the ecological balance of the environment. Therefore, systematic monitoring and effective remediation of these toxic pollutants either by adsorptive removal or by catalytic degradation are of great significance. From this viewpoint, porous organic polymers (POPs), being two- or three-dimensional polymeric materials, constructed from small organic molecules connected with rigid covalent bonds have come forth as a promising platform toward various leading applications, especially for efficient environmental remediation. Their unique chemical and structural features including high stability, tunable pore functionalization, and large surface area have boosted the transformation of POPs into various macro-physical forms such as thick and thin-film membranes, which led to a new direction in advanced level pollutant removal, separation and catalytic degradation. In this review, our focus is to highlight the recent progress and achievements in the strategic design, synthesis, architectural-engineering and applications of POPs and their composite materials toward environmental remediation. Several strategies to improve the adsorption efficiency and catalytic degradation performance along with the in-depth interaction mechanism of POP-based materials have been systematically summarized. In addition, evolution of POPs from regular powder form application to rapid and more efficient size and chemo-selective, "real-time" applicable membrane-based application has been further highlighted. Finally, we put forward our perspective on the challenges and opportunities of these materials toward real-world implementation and future prospects in next generation remediation technology.

Porous polymer magnetic adsorbents for dye wastewater treatment

Dye wastewater discharged from industries has caused serious environmental problems. The recent decade has witnessed adsorption technology emerging as an advanced dye wastewater treatment method with great potential Therefore, we fabricated two kinds of magnetic porous adsorbents (HSF and HSVF) with different specific surface areas and activity sites. Both of which exhibit excellent performance with remarkable dye adsorption capacities, especially HSVF. We further investigated their adsorption kinetic and isotherm in detail. Therein, HSVF showed a nice desorption capacity, and it could be recycled rapidly by magnetism, which exhibited the advantages of effective, easy operation, and low cost. In addition, their adsorption kinetic and isotherm were further studied and compared in detail. The results revealed that introducing strong active sites could improve both the adsorption capacity and rate effectively even though sacrificing part of specific surface areas, indicating that active sites might play a dominant role during the dye adsorption process.

Designed Construction of 2D Honeycomb Cationic MOF Materials for Selective Removal of Sulfonic Anionic Dyes

Various carcinogenic dyes in water bodies are difficult to degrade due to their stability to light and oxidants, causing extended pollution. In this study, MOF 1 ({[Co(tib)₂]·(H₂O)₂·SO₄}_n) and MOF 2 ({[Cu(tib)₂]·(H₂O)₂·SO₄}_n) (tib = 1,3,5-tirs(1-imidazolyl)benzene) were synthesized by the solvothermal method. MOFs 1 and 2 were successfully characterized by single-crystal X-ray diffraction (XRD) and powder X-ray diffraction (PXRD). Based on the structural characteristics of MOFs 1 and 2, we designed two cationic MOF material skeletons, namely, MOFs I and II ([Co(tib)₂²⁺]_n and [Cu(tib)₂²⁺]_n), which were obtained by calcination in combination with the thermogravimetric curve to remove the free components in the lattice. As expected, MOFs I and II showed an excellent adsorption effect on sulfonic anionic dyes. Notably, the adsorption capacity of MOF I can reach 2922.8 mg g^-1 for Congo Red (CR) at room temperature (RT). The adsorption process fits the pseudo-second-order kinetic model and Freundlich isotherm model. Moreover, zeta potential tests and quantum chemical calculations indicate that electrostatic interactions and hydrogen bond between the hydroxyl group on the sulfonic acid group and the N atom on the imidazole ring mainly promote the adsorption of CR dyes on MOF I. MOFs I and II are revealed as a promising novel adsorption material to remove hazardous organic aromatic pollutants with high efficiency in future endeavors.

Novel Carbazole-Based Porous Organic Polymer for Efficient Iodine Capture and Rhodamine B Adsorption

A new porous organic polymer (CTF-CAR), which takes carbazole as the electron-rich center unit and thiophenes as the auxiliary group, has been synthesized through catalyst-free Schiff-base polymerization. At the same time, the structure, thermal stability, morphology, and other basic properties of the polymer were analyzed by IR, NMR, TGA, and SEM. Then, CTF-CAR was applied to iodine capture and rhodamine B adsorption. Due to its strong electron donor ability and abundant heteroatom binding sites, which have a positive effect on the interaction between the polymer network and adsorbates, CTF-CAR exhibits high uptake capacities for iodine vapor and rhodamine B as 2.86 g g-1 and 199.7 mg g-1, respectively. The recyclability test also confirmed that it has good reusability. We found that this low-cost and catalyst-free synthetic porous organic polymer has great potential for the treatment of polluted water and iodine capture.

Porous Materials for Water Purification

Water pollution is a growing threat to humanity due to the pervasiveness of contaminants in water bodies. Significant efforts have been made to separate these hazardous components to purify polluted water through various methods. However, conventional remediation methods suffer from limitations such as low uptake capacity or selectivity, and current water quality standards cannot be met. Recently, advanced porous materials (APMs) have shown promise in improved segregation of contaminants compared to traditional porous materials in uptake capacity and selectivity. These materials feature merits of high surface area and versatile functionality, rendering them ideal platforms for the design of novel adsorbents. This Review summarizes the development and employment of APMs in a variety of water treatments accompanied by assessments of task-specific adsorption performance. Finally, we discuss our perspectives on future opportunities for APMs in water purification.

Engineering the Charge Density on an In2.77S4/Porous Organic Polymer Hybrid Photocatalyst for CO2-to-Ethylene Conversion Reaction

The development of an efficient photocatalyst for C2 product formation from CO₂ is of urgent importance toward the deployment of solar-fuel production. Here, we report a template-free, cost-effective synthetic strategy to develop a carbazole-derived porous organic polymer (POP)-based composite catalyst. The composite catalyst is comprised of In_2.77S₄ and porous organic polymer (POP) and is held together by induced-polarity-driven electrostatic interaction. Utilizing the synergy of the catalytically active In centers and light-harvesting POPs, the catalyst showed 98.9% selectivity toward the generation of C₂H₄, with a formation rate of 67.65 μmol g^-1 h^-1. Two different oxidation states of the In_2.77S₄ spinel were exploited for the C-C coupling process, and this was investigated by X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculations. The role of POP was elucidated via several photophysical and photoelectrochemical studies. The electron transfer was mapped by several correlated approaches, which assisted in establishing the Z-scheme mechanism. Furthermore, the mechanism of C₂H₄ formation was extensively investigated using density functional theory (DFT) calculations from multiple possible pathways.

Sulfonate-modified calixarene-based porous organic polymers for electrostatic enhancement and efficient rapid removal of cationic dyes in water

Developing of fast and efficient adsorbents for removal of low concentration refractory organics in water is significant. Herein, a novel calix[4]arene-based porous organic polymer CaPy is constructed through Sonogashira-Hagihara cross-coupling polycondensation. The strong polar sulfonate is further anchored onto the polymer skeleton of CaPy and three sulfonate-modified anionic polymers CaPy-S1, CaPy-S2, and CaPy-S3 were obtained and fully characterized. The adsorption isotherms showed that the maximum adsorption capacities of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward methylene blue (MB) were 270, 1454, 558 and 1381 mg g^-1, whereas those for Rhodamine B (RhB) were 183, 2653, 1132, and 1796 mg g^-1, respectively. The maximum adsorption capacity toward RhB was the highest reported vale among the currently used synthetic adsorbents. In addition, the pseudo-second-order rate constants of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward MB were 0.00572, 0.488, 2.24, and 0.192 g mg^-1 min^-1, respectively, and those toward RhB were 0.000234, 0.138, 0.0819, and 0.203 g mg^-1 min^-1, respectively. The pseudo-second-order rate constant of CaPy-S2 toward MB was 2.24 g mg^-1 min^-1 indicating one of the highest adsorption speeds. The activation energy of CaPy-S1 for RhB and MB were 121 and 109 kJ mol^-1, respectively, demonstrating that the adsorption of both dyes on CaPy-S1 was chemisorption process. Further, the obtained values of Gibbs free energy were negative, revealing that the adsorption process was spontaneous. This work provides an effective approach for improving adsorption performance via post-modification.

Bimetallic CuPd alloy nanoparticles decorated ZnO nanosheets with enhanced photocatalytic degradation of methyl orange dye

Photocatalytic technology is widely explored as a promising alternative for water treatments. However, low photocatalytic efficiency and selectivity usually limit its practical application. Herein, we develop the synthesis of two-dimensional zinc oxide (ZnO) nanosheets decorated with copper (Cu)-palladium (Pd) bimetallic nanoparticles (NPs) for the degradation of organic dyes in an aqueous solution. Compared to pristine ZnO nanosheets, the prepared CuPd/ZnO composites exhibited superior performance for the photocatalytic degradation of organic dyes under visible-light irradiation. The remarkable improvement of degradation activity was attributable to the enhanced separation and transfer efficiency of photogenerated charge carriers. The highest catalytic efficiency of CuPd/ZnO nanocomposite with the CuPd content of 0.5 wt% exhibited 95.3% removal of methyl orange (MO) (40 mg/L) within 45 min. From the experimental data, we believe this study provides a new avenue for the design and fabrication of high-performance photocatalysts capable of water treatments.

A pyridinium functionalization chitosan for efficient elimination of methyl orange and Cr(VI)

A pyridinium functionalization chitosan (PCS) at high yield was facilely and solvothermally obtained from reactions of chitosan with N-2,4-dinitrophenyl-pyridinium chloride. The morphology and physical-chemical properties of PCS were tested with various techniques. Its sorption behaviors towards methyl orange (MO) and Cr(VI) were systematically investigated. Pseudo-second-order kinetic and Langmuir equations well fitted the sorption kinetics and isotherms, respectively. Thermodynamics analyses revealed the spontaneous and endothermic sorption of these two contaminants. PCS exhibited high sorption capacity of 1649.30 mg·g^-1 MO and 200.46 mg·g^-1 Cr(VI) at 308 K. The superior sorption performance of PCS over MO is ascribed to ion exchange, intermolecular hydrogen bond, and electrostatic and π-π interactions, while sorption of PCS over Cr(VI) is mainly driven by electrostatic forces, reduction and ion exchange. Moreover, the PCSexceeded 95 % of its original capacities during five cycles. This high sorption capacities and high reusability make PCS an excellent sorbent candidate towards anionic contaminants.

Nickel and iron-based metal-organic frameworks for removal of organic and inorganic model contaminants

Metal-organic frameworks (MOFs) are a promising class of porous nanomaterials in the field of environmental remediation. Ni-MOF and Fe-MOF were chosen for their advantages such as structural robustness and ease of synthesis route. The structure of prepared MOFs was characterized using FE-SEM, XRD, FTIR, and N₂ adsorption-desorption. The efficiency of MOFs to remove organic model contaminants (anionic Alizarin Red S (ARS) and cationic malachite green (MG) and inorganic fluoride was studied. Fe-MOF and Ni-MOF adsorbed 67, 88, 6% and 32, 5, and 9% of fluoride, ARS, and MG, respectively. Further study on ARS adsorption by Fe-MOF showed that the removal efficiency was high in a wide range of pH from 3 to 9. Moreover, dye removal was directly increased by adsorbent mass (0.1-0.75 g/L) and decreased by ARS concentration (25-100 mg/L). The pseudo-first-order kinetic model and Langmuir isotherm model with a q_max of 176.68 mg/g described the experimental data well. The separation factor, K_L, was in the range of 0-1, which means the adsorption process was favorable. In conclusion, Fe-MOF showed remarkable adsorption of organic and inorganic model contaminants.

Applications of functionalized magnetic biochar in environmental remediation: A review

Magnetic biochar (MBC) is extensively applied on contaminants removal from environmental medium for achieving environmental-friendly remediation with reduction of secondary pollution owing to its easy recovery and separation. However, the summary of MBC synthesis methods is still lack of relevant information. Moreover, the adsorption performance for pollutants by MBC is limited, and thus it is imperative to adopt modification techniques to enhance the removal ability of MBC. Unfortunately, there are few reviews to present modification methods of MBC with applications for removing hazardous contaminants. Herein, we critically reviewed (i) MBC synthetic methods with corresponding advantages and limitations; (ii) adsorption mechanisms of MBC for heavy metals and organic pollutants; (iii) various modification methods for MBC such as functional groups grafting, nanoparticles loading and element doping; (iv) applications of modified MBC for hazardous contaminants adsorption with deep insight to relevant removal mechanisms; and (v) key influencing conditions like solution pH, temperature and interfering ions toward contaminants removal. Finally, some constructive suggestions were put forward for the practical applications of MBC in the near future. This review provided a comprehensive understanding of using functionalized MBC as effective adsorbent with low-cost and high-performance characteristics for contaminated environment remediation.

Highly Efficient Organic Dyes Capture Using Thiol-Functionalized Porous Organic Polymer

It is of great significance to develop new materials for efficient capture cationic dyes methylene blue (MB) and malachite green (MG). In this work, a novel triptycene-based porous organic polymer with abundant thiol groups (TPP-SH) was prepared successfully by postmodification with a high surface area and robust triptycene-based porous organic polymer (TPP). The obtained TPP-SH exhibited a high surface area, good porosity, and good thermal stability. In addition, TPP-SH was highly effective at capturing MB and MG from aqueous solution because of the abundant thiols in its hierarchical structure. Under optimal adsorption conditions, the maximum adsorption capacities of MB and MG calculated by the Langmuir model at room temperature were 1146.3 and 689.6 mg g-1, respectively. These values are higher than those of many reported materials. The MB and MG adsorption rates were 0.0154 and 6.69 × 10-4 mg g-1 min-1, respectively. Furthermore, the polymer TPP-SH had a good recycling performance after adsorption-desorption at least five times. Therefore, the TPP-SH exhibited a high adsorption capacity, fast adsorption kinetics, and easy-recycling behavior, providing a new avenue for the preparation of green functionalized adsorbents with good performance for water decontamination.

Emulsion-Templated Porous Polymers for Efficient Dye Removal

A high internal phase emulsion (HIPE) method was used to produce adsorbents with an interconnected porous structure. HIPE was prepared using vinyl benzyl chloride (VBC), divinylbenzene (DVB), tert-butyl acrylate, and Span80 as the organic phase and water with K₂S₂O₈ and CaCl₂ as the water phase. The polymerization of the organic phase produced highly porous polymers called polyHIPE, carrying two functional groups. As a result of the template method, polyHIPEs have a low surface area. To overcome this drawback, polyHIPE was hyper-cross-linked through VBC to create meso- and micropores, resulting in a higher surface area. Then the polymer surface was tailored with carboxylic acid groups by simple hydrolysis of tert-butyl acrylate. The adsorption performances of the acidic functional hyper-cross-linked polyHIPEs prepared for the various reaction times of 0, 15, and 60 min were compared for methylene blue. The hyper-cross-linked polyHIPEs showed an enhanced adsorption kinetics for methylene blue, and the 15 min hyper-cross-linking reaction increased the rate of methylene blue adsorption significantly. It was proven that the polyHIPE adsorbent can be reused by treating it with an aqueous acidic solution in ethanol.

Modulation of photocatalytic properties through counter-ion substitution: tuning the bandgaps of aromatic sulfonium octamolybdates for efficient photo-degradation of rhodamine B

Modulating the photocatalytic properties of polyoxometalate-organic hybrids through counterion substitution is a less explored concept. In this study, a new series of aromatic sulfonium counterions (ASCs) having the general formula X-C₆H₄-S(Me₂)⁺, where X represents different functional substituents such as -H, -Cl, -Me, and -CHO at the para-position of the sulfonium moiety on a benzene ring, have been used for fine-tuning the optical bandgaps and adsorption properties of octamolybdate [Mo₈O₂₆]^4- hybrids for photocatalytic dye degradation applications. The photodegradation of rhodamine B (RhB) is used as a model reaction, which follows pseudo-first-order kinetics exhibiting counterion-dependent degradation rate constants. The hybrid catalyst bearing a -CHO substituent on the ASC showed the lowest bandgap (2.91 eV) and the highest degradation rate constant (0.0141 min^-1) of the series. A possible mechanism of photocatalytic dye degradation by hybrids involving the generation of reactive oxygen species (ROS) has been proposed, supported by radical scavenging studies. The intermediates formed during the photodegradation of RhB were analyzed and identified using electrospray ionization mass spectrometry (ESI-MS). The present study reveals a new strategy for tuning the photocatalytic properties of hybrids using differently functionalized ASCs and opens up new avenues for novel POM-hybrids as potential photocatalysts for environmental remediation applications.

Nanostructured Hypercrosslinked Porous Organic Polymers: Morphological Evolution and Rapid Separation of Polar Organic Micropollutants

Nanostructured hypercrosslinked porous organic polymers have triggered immense research interest for a broad spectrum of applications ranging from catalysis to molecular separation. However, it still remains a challenge to tune their nanoscale morphology. Herein, we demonstrated a remarkable variation of morphologies of triptycene-based hypercrosslinked microporous polymers starting from irregular aggregates (FCTP) to rigid spheres (SCTP) to two-dimensional nanosheets (SKTP) from three distinct polymerization methodologies, Friedel-Crafts knitting using an external crosslinker, Scholl reaction, and solvent knitting, respectively. Further, the dramatic role of reaction temperatures, catalysts, and solvents resulting in well-defined morphologies was elucidated. Mechanistic investigations coupled with microscopic and computational studies revealed the evolution of 2D nanosheets of a highly porous solvent-knitted polymer (SKTP, 2385 m² g^-1), resulting from the sequential hierarchical self-assembly of nanospheres and nanoribbons. A structure-activity correlation of hypercrosslinked polymers and their sulfonated counterparts for the removal of toxic polar organic micropollutants from water was delineated based on the chemical functionalities, specific surface area, pore size distribution, dispersity, and nanoscale morphology. Furthermore, a sulfonated 2D sheet-like solvent-knitted polymer (SKTPS) exhibited rapid adsorption kinetics (within 30 s) for a large array of polar organic micropollutants, including plastic components, steroids, antibiotic drugs, herbicides, and pesticides with remarkable uptake capacity and excellent recyclability. The current study provides the impetus for designing morphology-controlled functionalized porous polymers for task-specific applications.

A novel porous hollow carboxyl-polysulfone microsphere for selective removal of cationic dyes

Herein, we obtained porous hollow carboxyl-polysulfone (PH-CPSF) microspheres through non-solvent-induced phase separation (NIPS) method and simple modification, used as highly efficient adsorbents for removing cationic dyes from sewage. The resulting PH-CPSF microspheres possess a hollow core and sponge-like shell structure, with high surface area, durable chemical inertness and structural stability. The as-synthesized PH-CPSF microspheres deliver a desirable adsorption effect after deprotonation treatment, with an adsorption capacity reaching up to 154.5 mg g^-1 at 25 °C (pH = 7) of methylene blue (MB). The inter-molecular interactions between MB and the surface of the PH-CPSF, including π-π interaction, hydrogen bonding, strong charge attraction and weak charge attraction endow the adsorption ability of the PH-CPSF. The pseudo-second-order kinetic model pronounces in the adsorption behavior, and the adsorption equilibrium data is fitted to the Langmuir model. Moreover, PH-CPSF microspheres can also be used as adsorption fillers for large-scale water purification, and a removal rate of 94.0% for MB can be achieved under a flow rate of 8000 L m^-3 h^-1. The reusability of 95.3% removal effect for PH-CPSF microspheres after 20 consecutive cycles can be attained by a simple regeneration treatment. The adsorption efficiency of the PH-CPSF microspheres was evaluated by variety of cationic and anionic dyes, with high adsorption capacity toward cationic dyes (100%) and less than 10% toward anionic dyes. These results manifest that PH-CPSF microspheres are a potential adsorbent with long-term purification capabilities, which are expected to be used in small and large-scale sewage treatment.

Hollow Polyaniline Microsphere/MnO2/Fe3O4 Nanocomposites in Adsorptive Removal of Toxic Dyes from Contaminated Water

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO₂/Fe₃O₄ composites by in situ deposition of MnO₂ and Fe₃O₄ nanoparticles on the surface of PNHM. The physicochemical characteristics and adsorption behavior of the prepared PNHM/MnO₂/Fe₃O₄ composites towards the removal of toxic methyl green (MG) and Congo red (CR) dyes have been investigated. The characterization study revealed the successful synthesis of the prepared PNHM/MnO₂/Fe₃O₄ adsorbent with a high Brunauer-Emmett-Teller (BET) surface area of 191.79 m²/g. The batch adsorption study showed about 88 and 98% adsorption efficiencies for MG and CR dyes, respectively, at an optimum dose of 1 g/L of PNHM/MnO₂/Fe₃O₄ at pH ∼6.75 at room temperature (303 ± 3 K). The adsorption phenomena of MG and CR dyes were well described by the Elovich and pseudo-second-order kinetics, respectively, and Freundlich isotherm model. The thermodynamics study shows that the adsorption reactions were endothermic and spontaneous in nature. The maximum adsorption capacity (Q_max) for MG and CR dyes was observed as 1142.13 and 599.49 mg/g, respectively. The responsible adsorption mechanisms involved in dye removal were electrostatic interaction, ion exchange, and the formation of the covalent bonds. The coexisting ion study revealed that the presence of phosphate co-ion considerably reduced the CR dye removal efficiency. However, the desorption-regeneration study demonstrated the successful reuse of the spent PNHM/MnO₂/Fe₃O₄ material for the adsorption of MG and CR dyes for several cycles. Given the aforementioned findings, the PNHM/MnO₂/Fe₃O₄ nanocomposites could be considered as a promising adsorbent for the remediation of dye-contaminated water.

Conducting polymer hydrogels as a sustainable platform for advanced energy, biomedical and environmental applications

Environmentally friendly polymeric materials and derivative technologies play increasingly important roles in the sustainable development of our modern society. Conducting polymer hydrogels (CPHs) synergizing the advantageous characteristics of conventional hydrogels and conducting polymers are promising to satisfy the requirements of environmental sustainability. Beyond their use in energy and biomedical applications that require exceptional mechanical and electrical properties, CPHs are emerging as promising contaminant adsorbents owing to their porous network structure and regulable functional groups. Here, we review the currently available strategies for synthesizing CPHs, focusing primarily on multifunctional applications in energy storage/conversion, biomedical engineering and environmental remediation, and discuss future perspectives and challenges for CPHs in terms of their synthesis and applications. It is envisioned to stimulate new thinking and innovation in the development of next-generation sustainable materials.

Multifunctional Zn-Ln (Ln = Eu and Tb) heterometallic metal-organic frameworks with highly efficient I2 capture, dye adsorption, luminescence sensing and white-light emission

A new family of isostructural 3d-4f heterometallic metal-organic frameworks (HMOFs), [Zn₃Eu_xTb_2-x(TZI)₄(DMA)₅(H₂O)₃]·4DMA [x = 0 (1), 0.3 (2), 0.6 (3), 0.9 (4), 1 (5), 1.2 (6), 1.5 (7), 1.8 (8), 2 (9)], has been synthesized using the 5-(4-(tetrazol-5-yl) phenyl)isophthalic acid (H₃TZI) ligand, Ln^III ions and Zn^II ions under solvothermal conditions. All HMOFs exhibit a (3,3,4,5,5)-connected 6³·6³(4²·6²·8²)(4·6⁵·8)(4·6⁶·8³) topology, which features three different types of motifs: one is a mononuclear Zn^II ion and the other two motifs are binuclear [Zn(COO)₃Ln] clusters. The adsorption experiments indicate that Zn₃Tb₂ (1) could efficiently remove almost all I₂ from cyclohexane solution after 12 h and also showed better adsorption towards neutral red (NR) dye (adsorption: only the Zn₃Tb₂ (1) was taken as one representative). Simultaneously, the luminescence sensing showed that Zn₃Tb₂ (1) and Zn₃Eu₂ (9) have excellent response and sensitivity towards pollutants such as Fe³⁺ ions and 2,4,6-trinitrophenol (TNP) with high selectivity and a fairly low limit of detection through luminescence quenching effect. Moreover, seven trimetallic-doped HMOFs 2-8 analogues of Zn₃Ln₂ (single) HMOFs were designed and prepared, showing different changes of luminescent color. More interestingly, Zn₃Eu_1.5Tb_0.5 (7) with white-light emission was fabricated by doping relative concentrations of Eu³⁺ and Tb³⁺ ions. To the best of our knowledge, Zn₃Eu_1.5Tb_0.5 (7) represents a novel kind of heterometallic Zn₃Ln₂ HMOFs with white-light emission. It could be deduced that the excellent characteristics, namely strong typical luminescence emission of Zn^II and Ln^III ions, microporous channels, active open metal sites (tetra-coordinated Zn^II-metal sites), and uncoordinated carboxylate O atoms and uncoordinated tetrazolate N atoms, made the above HMOFs an ideal platform for adsorption, luminescence sensing, and white-light emission. More significantly, these HMOFs are the first reported Zn-Ln heterometallic materials with the H₃TZI ligand.

Hydroxyl modified hypercrosslinked polymers: targeting high efficient adsorption separation towards aniline

The removal of aniline from aqueous solution has a major environmental impact and attracted increasing attention in last few years.