Removal of Organic Micropollutants from Water by Macrocycle‐Containing Covalent Polymer Networks

β-Cyclodextrin based magnetic hyper-crosslinked polymer: A recyclable adsorbent for effective preconcentration of triazine herbicides in complex sample matrices

High efficiency enrichment and trace analysis of triazine herbicide residues are crucial for ensuring environmental and food safety. Herein, a series of magnetic hyper-crosslinked polymers (CD-gs-MHCPs) were synthesized with different crosslinkers, which might possess different pore structure and surface area, so they might dispay variable adsorption performance. CD-gs-MHCP2 with dichloroxylene as crosslinker delivered superior adsorption ability for triazine herbicides (THs). The synergistic effect of hydrogen bonds, hydrophobic interaction, π-π stacking interaction and pore adsorption were proved to be the main adsorption mechanism. Combined CD-gs-MHCP2 based magnetic solid-phase extraction (MSPE) with high-performance liquid chromatography, the quantitative analysis of THs in river water and vegetable samples (zucchini, pakchoi) was achieved. Under the optimal conditions, the enrichment factors for three different samples ranged from 94 to 244 and low detection limit (S/N = 3) of the four THs were obtained from 0.05 to 0.15 ng mL-1 for river water and 0.31-3.10 ng g-1 for vegetable samples. The method recoveries were in the range of 86.2 %-120 % with relative standard deviations lower than 7.4 %. This work not only offers a new strategy for fabrication β-CD-based HCPs, but also provided a practical and effective method for efficient isolation and sensitive detection of trace THs residues in complex samples.

Porous β-cyclodextrin polymers for rapid and efficient removal of organic micropollutants from water: The role of sulfonation and porosity on adsorption performance

Removal of organic micropollutants (OMPs) from water, especially hydrophilic and ionized ones, is challenging for water remediation. Herein, porous β-cyclodextrin polymers (PCPs) with tailored functionalization were prepared based on molecular expansion strategy and sulfonation. Partially benzylated β-cyclodextrin was knotted by external crosslinker to form PCP1, and knotting PCP1 by expansion molecule generated PCP2. PCP1 and PCP2 were sulfonated to achieve PCP1-SO3H and PCP2-SO3H. Based on systematical adsorption evaluation toward multiple categories of OMPs, it was found that the introduced strong polar -SO3H group could bring strong hydrogen bonding and electrostatic interactions. PCP2 showed the highest surface (998.97 m2/g) displayed more excellent adsorption performance toward neutral and anionic OMPs, and the adsorption mechanism for this property of PCP2 was dominated by hydrophobic interactions. In addition, the PCP1-SO3H with the lowest surface area (39.75 m2/g) rather than PCP2-SO3H with higher surface (519.28 m2/g) exhibited more superior adsorption towards hydrophilic and cationic OMPs, benefiting by hydrogen bonding and electrostatic interactions as well as appropriate porosity. These results not only confirmed the performance enhancement of PCPs through the integration of novel preparation strategy, but also provided fundamental guidance for PCPs design for water remediation.

Hydrophobicity Promoted Efficient Hydroxyl Radical Generation in Visible-Light-Driven Photocatalytic Oxidation

Hydroxyl radical (•OH) with strong oxidation capability is one of the most important reactive oxygen species. The generation of •OH from superoxide radicals (•O2 -) is an important process in visible-light-driven photocatalysis, but the conversion generally suffers from slow reaction kinetics. Here, a hydrophobicity promoted efficient •OH generation in a visible-light-driven semiconductor-mediated photodegradation reaction is reported. Hydrophobic TiO2 that is synthesized by modifying the TiO2 surface with a thin polydimethylsiloxane (PDMS) layer and rhodamine B (RhB) are used as model semiconductors and dye molecules, respectively. The surface hydrophobicity resulted in the formation of a solid-liquid-air triphase interface microenvironment, which increased the local concentration of O2. In the meanwhile, the saturated adsorption quantity of RhB on hydrophobic TiO2 is improved by five-fold than that on untreated TiO2. These advantages increased the density of the conduction band photoelectrons and •O2 - generation, and stimulated the conversion of •O2 - to •OH. This consequently not only increased the kinetics of the photocatalytic reaction by an order of magnitude, but also altered the oxidation route from conventional decolorization to mineralization. This study highlights the importance of surface wettability modulation in boosting •OH generation in visible-light-driven photocatalysis.

Ionic Covalent Organic Frameworks in Adsorption and Catalysis

The ion extraction and electro/photo catalysis are promising methods to address environmental and energy issues. Covalent organic frameworks (COFs) are a class of promising template to construct absorbents and catalysts because of their stable frameworks, high surface areas, controllable pore environments, and well-defined catalytic sites. Among them, ionic COFs as unique class of crystalline porous materials, with charges in the frameworks or along the pore walls, have shown different properties and resulting performance in these applications with those from charge-neutral COFs. In this review, current research progress based on the ionic COFs for ion extraction and energy conversion, including cationic/anionic materials and electro/photo catalysis is reviewed in terms of the synthesis strategy, modification methods, mechanisms of adsorption and catalysis, as well as applications. Finally, we demonstrated the current challenges and future development of ionic COFs in design strategies and applications.

Smart pillar[5]arene-based PDMAEMA/PES beads for selective dye pollutants removal: design, synthesis, chemical-physical characterization, and adsorption kinetic studies

This article reports on the synthesis of an innovative smart polymer, P5-QPDMAEMA, opportunely developed with the aim of combining the responsiveness of PDMAEMA polymer and the host-guest properties of covalently linked pillar[5]arenes. Thanks to a traditional Non-Induced Phase Separation (NIPS) process performed at various coagulation pH, the blending of P5-QPDMAEMA with polyethersulfone gave rise to the formation of functional beads for the removal of organic dyes in water. Adsorption tests are carried out on all the produced blend-based beads by employing two representative dyes, the cationic methylene blue (MB), and the anionic methyl orange (MO). In particular, the P5-QPDMAEMA based beads, prepared at acidic pH, featured the best MO removal rate (i. e., 91.3 % after 150 minutes starting from a 20 mg ⋅ L-1 solution) and a high selectivity towards the removal of the selected anionic dye. Based on the adsorption kinetics and isotherm calculations, the pseudo-first order and Freundlich models were shown to be the most suitable to describe the MO adsorption behavior, achieving a maximum adsorption capacity of 21.54 mg ⋅ g-1. Furthermore, zwitterionic beads are obtained by a post-functionalization of the PDMAEMA and the P5-QPDMAEMA based beads, to test their removal capability towards both anionic and cationic dyes, as shown.

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

The metastable liquid properties and chemical bonds beyond 2000 K remain a huge challenge for ground-based research on liquid materials chemistry. We show the strong undercooling capability, metastable liquid properties and surface wave patterns of refractory Nb-Si and Zr-V binary alloys explored in space environment. The floating droplet of Nb82.7Si17.3 eutectic alloy superheated up to 2338 K exhibited an extreme undercooling of 437 K, approaching the 0.2TE threshold for homogeneous nucleation of liquid-solid reaction. The microgravity state endowed alloy droplets with nearly perfect sphericity and thus ensured the high accuracy to determine metastable undercooled liquid properties. A special kind of swirling flow was induced for liquid alloy owing to Marangoni convection, which resulted in the spiral microstructures on Zr64V36 alloy surface during liquid-solid phase transition. The coupled impacts of surface nucleation and surface flow brought in a novel olivary shape for these binary alloys. Furthermore, the chemical bonds and atomic structures of high temperature liquids were revealed to understand the liquid properties in outer space circumstances.

The paradigm for exceptional iodine capture by nonporous amorphous electron-deficient cyclophanes

Nuclear power emerges as a beacon of hope in tackling the energy crisis. However, the emission of radioactive iodine originating from nuclear waste and accidents poses a serious danger to nature and human well-being. Therefore, it becomes imperative to urgently develop suitable adsorbents capable of iodine capture and long-term storage. It's generally recognized that achieving high iodine capture efficiency necessitates the presence of electron-rich pores/cavities that facilitate charge-transfer (CT) interactions, as well as effective sorption sites capable of engaging in lone pair interactions with iodine. In this study, an unprecedented iodine capture paradigm by nonporous amorphous electron-deficient tetracationic cycloalkanes in vapor and aqueous solutions is revealed, overturning preconceived notions of iodine trapping materials. A newly reported tetracationic cyclophane, BPy-Box4+, exhibited an exceptional iodine vapor sorption capacity of 3.99 g g-1, remarkable iodine removal efficiency in aqueous media, and outstanding reusability. The iodine capture mechanism is unambiguously elucidated by theoretical calculations and the single-crystal structures of cyclophanes with a gradual increase in iodine content, underlining the vital role of host-guest (1:1 or 1:2) interactions for the enhanced iodine capture. The current study demonstrates a new paradigm for enhanced iodine capture by nonporous amorphous electron-deficient cyclophanes through host-guest complexation.

Recent progress in iodine capture by macrocycles and cages

The effective capture of radioiodine is vital to the development of the nuclear industry and ecological environmental protection. There is, therefore, a continuously growing research exploration in various types of solid-state materials for iodine capture. During the last decade, the potential of using macrocycle and cage-based supramolecular materials in effective uptake and separation of radioactive iodine has been demonstrated. Interest in the application of these materials in iodine capture originates from their diversified porous characteristics, abundant host-guest chemistry, high iodine affinity and adsorption capacity, high stability in various environments, facile modification and functionalization, and intrinsic structural flexibility, among other attributes. Herein, recent progress in macrocycle and cage-based solid-state materials, including pure discrete macrocycles and cages, and their polymeric forms, for iodine capture is summarized and discussed with an emphasis on iodine capture capacities, mechanisms, and design strategies.

Thioether-functionalized porous β-cyclodextrin polymer for efficient removal of heavy metal ions and organic micropollutants from water

Herein, a thioether-functionalized porous β-cyclodextrin polymer (P(Bn-S-CD)) was prepared for efficient removal of heavy metal ions and organic micropollutants (OMPs) from water. P(Bn-S-CD) showed a surface area of 763 m2/g and a sulfur content 5.83 wt%. Based on screening studies, Hg2+ and diclofenac sodium (DS) were selected as model pollutants. P(Bn-S-CD) could adsorb Hg2+ and DS simultaneously, while the adsorbed Hg2+ afforded positive charges to the primary rims of CDs, greatly enhancing the adsorption rate and adsorption capacity of DS. Although the adsorbed DS showed no obvious effect on Hg2+ adsorption, it improved the affinity of Hg2+ upon P(Bn-S-CD). Adsorption mechanism studies confirmed the essential role of electrostatic interactions for these results. P(Bn-S-CD) also showed good selectivity towards heavy metal ions, excellent adsorption performance in real water at environmental levels and good reusability, implying great promise for water treatment.

Selectively transport and removal of fluoride ion by pillar[5]arene polymer-filled nanochannel membrane

Excess fluoride ions in groundwater accumulate through the roots of crops, affecting photosynthesis and inhibiting their growth. Long-term bioaccumulation also threatens human health because it is poorly degradable and toxic. Currently, one of the biggest challenges is developing a unique material that can efficiently remove fluoride ions from the environment. The excellent properties of functionalized pillar[5]arene polymer-filled nanochannel membranes were explored to address this challenge. Constructing a multistage porous nanochannel membrane, consisting of microscale etched nanochannels and nanoscale pillar[5]arene cross-linked polymer voids. A fluoride removal rate of 0.0088 mmol ⋅ L-1  ⋅ min-1 was achieved. Notably, this rate surpassed the rates observed with other control ions by a factor of 6 to 8.8. Our research provides a new direction for developing water fluoride ion removal materials.

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.

Upgraded β-cyclodextrin-based broad-spectrum adsorbents with enhanced antibacterial property for high-efficient dyeing wastewater remediation

The dyeing wastewater contains amounts of refractory organic compounds, and severely endangers the ecosystem and human health. To alleviate this problem, in this study, the low-cost broad-spectrum nano-adsorbent (denoted as CD/CA-g-CS) with strong antibacterial activity has been synthesized by chemical binding of β-cyclodextrin (β-CD) with chitosan (CS) and citric acid (CA) for high-efficient dyes scavenger. Taking advantage of the extraordinary water insolubility, porous nature and abundant surface groups, the synthesized CD/CA-g-CS outperforms the previously reported adsorbents in terms of adsorption performance. The CD/CA-g-CS exhibits ultrahigh adsorption capacities of 801.66, 770.50 and 946.66 mg/g, respectively mg/g for the cationic dyes of malachite green (MG), basic red (BR) and methylene blue (MB), respectively, while 389.64, 619.60 and 429.22 mg/g for the anionic dyes of acid blue (AB), acid red (AR) and acid yellow (AY), respectively. The chemical monolayer absorption is further demonstrated by the analysis based on the pseudo-second-order adsorption kinetics and Langmuir isotherm models. The regenerable CD/CA-g-CS not only performs well in one-step removal of the mixed dyes in the simulated sewage, but also exhibits superior performance in purifying real industrial wastewater. Moreover, CD/CA-g-CS endowed with antibacterial activity leads to an inhibition rate of over 99.99 % for E. coli. The newly developed CD/CA-g-CS adsorbents are highly promising for high-efficient dyeing wastewater remediation.

Pillararene-Based Supramolecular Polymers for Adsorption and Separation

Supramolecular polymers have attracted increasing attention in recent years due to their perfect combination of supramolecular chemistry and traditional polymer chemistry. The design and synthesis of macrocycles have driven the rapid development of supramolecular chemistry and polymer science. Pillar[n]arenes, a new generation of macrocyclic compounds possessing unique pillar-shaped structures, nano-sized cavities, multi-functionalized groups, and excellent host-guest complexation abilities, are promising candidates to construct supramolecular polymer materials with enhanced properties and functionalities. This review summarizes recent progress in the design and synthesis of pillararene-based supramolecular polymers (PSPs) and illustrates their diverse applications as adsorption and separation materials. All performances are evaluated and analyzed in terms of efficiency, selectivity, and recyclability. Typically, PSPs can be categorized into three typical types according to their topologies, including linear, cross-linked, and hybrid structures. The advances made in the area of functional supramolecular polymeric adsorbents formed by new pillararene derivatives are also described in detail. Finally, the remaining challenges and future perspectives of PSPs for separation-based materials science are discussed. This review will inspire researchers in different fields and stimulate creative designs of supramolecular polymeric materials based on pillararenes and other macrocycles for effective adsorption and separation of a variety of targets.

Enhanced Mass Transfer of Ozone and Emerging Pollutants through a Gas-Solid-Liquid Reaction Interface for Efficient Water Decontamination

Ozone (O3), as an environmentally friendly oxidant, is widely used to remove emerging pollutants and ensure the safety of the water supply, whereas the restricted accessibility of O3 and limited collision frequency between pollutants and O3 will inevitably reduce the ozonation efficiency. To promote the chemical reactions between O3 and target pollutants, here we developed a novel gas-solid-liquid reaction interface dominated triphase ozonation system using a functional hydrophobic membrane with an adsorption layer as the O3 distributor and place where chemical reactions occurred. In the triphase system, the functional hydrophobic membrane simultaneously improved the interface adsorption performance of emerging pollutants and the access pathway of O3, leading to a marked enhancement of interfacial pollutant concentration and O3 levels. These synergistic qualities result in high ciprofloxacin (CIP) removal efficiency (94.39%) and fast apparent reaction rate constant (kapp, 2.75 × 10-2 min-1) versus a traditional O3 process (41.82% and 0.48 × 10-2 min-1, respectively). In addition, this triphase system was an advanced oxidation process involving radical participation and showed excellent degradation performance of multiple emerging pollutants. Our findings highlight the importance of gas-solid-liquid triphase reaction interface design and provide new insight into the efficient removal of emerging pollutants by the ozonation process.

Tailoring carboxylatopillar[5]arene-modified magnetic graphene oxide nanocomposites for the efficient removal of cationic dyes

A carboxylatopillar[5]arene-embellished (CP5) magnetic graphene oxide nanocomposite (MGO@CP5) was smoothly constructed via a mild layer-by-layer method. The morphology, structure, and surface characteristics of this nanocomposite was investigated by field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, zeta potential, and other techniques. Benefiting from a high capture ability for small molecules of CP5 as a supramolecular host molecule, along with a negative surface charge and large surface area of MGO@CP5, this nanocomposite exhibits an ultrafast, efficient adsorption property for representative cationic dyes: methylene blue (MB) and basic fuchsin (BF). The removal efficiency of MB and BF can reach nearly 99% within 3 min, while the maximum adsorption capacity of the two dyes reaches 240 mg g-1 for MB and 132 mg g-1 for BF. Furthermore, owing to excellent magnetic responsiveness from the tight loading of Fe3O4 nanoparticles on graphene oxide, MGO@CP5 could be easily and magnetically separated, regenerated, and reused four times without an evident reduction in the removal efficiency (>95%). Impressively, the adsorption property of MGO@CP5 reveals a strong tolerance to pH changes and ionic strength interference, which renders it a promising adsorbent in the field of water treatment.

The Specific Removal of Perfluorooctanoic Acid Based on Pillar[5]arene-Polymer-Packed Nanochannel Membrane

The conspicuous surface activity and exceptional chemical stability of perfluorooctanoic acid, commonly referred to as PFOA, have led to its extensive utilization across a broad spectrum of industrial and commercial products. Nonetheless, significant concerns have arisen regarding the environmental presence of PFOAs, driven by their recognized persistence, bioaccumulative nature, and potential human health risks. In the realm of sustainable agriculture, a pivotal challenge revolves around the development of specialized materials capable of effectively and selectively eliminating PFOA from the environment. This study proposes harnessing the exceptional properties of a pillar[5]arene polymer to construct a nanochannel membrane filled with tryptophan-alanine dipeptide pillar[5]arene polymer. Through the functionalization of these nanochannel membranes, we achieved a PFOA removal rate of 0.01 mmol L-1 min-1, surpassing the rates observed with other control chemicals by a factor of 4.5-15. The research on PFOA removal materials has been boosted because of the creation of this highly selective PFOA removal membrane.

Magnetic Covalent Organic Framework Composites for Wastewater Remediation

Covalent organic frameworks (COFs) with high specific surface area, tailored structure, easy functionalization, and excellent chemical stability have been extensively exploited as fantastic materials in various fields. However, in most cases, COFs prepared in powder form suffer from the disadvantages of tedious operation, strong tendency to agglomerate, and poor recyclability, greatly limiting their practical application in environmental remediation. To tackle these issues, the fabrication of magnetic COFs (MCOFs) has attracted tremendous attention. In this review, several reliable strategies for the fabrication of MCOFs are summarized. In addition, the recent application of MCOFs as outstanding adsorbents for the removal of contaminants including toxic metal ions, dyes, pharmaceuticals and personal care products, and other organic pollutants is discussed. Moreover, in-depth discussions regarding the structural parameters affecting the practical potential of MCOFs are highlighted in detail. Finally, the current challenges and future prospects of MCOFs in this field are provided with the expectation to boost their practical application.

Sulfonated polyhedral oligomeric silsesquioxane-cyclodextrin hybrid polymers for efficient removal of micropollutants from water

Herein, β-cyclodextrin-containing hybrid polymers (P1, P2 and P3) were prepared through crosslinking partially benzylated β-cyclodextrin (PBCD) by octavinylsilsesquioxane (OVS). P1 stood out in screening studies and the residual hydroxyl groups of PBCD was sulfonate-functionalized. The obtained P1-SO₃Na showed greatly enhanced adsorption towards cationic MPs and maintained the excellent adsorption performance towards neutral MPs. The rate constants (k₂) of cationic MPs upon P1-SO₃Na were 9.8-34.8 times larger than those upon P1. The equilibrium uptakes of the neutral and cationic MPs upon P1-SO₃Na were above 94.5 %. Meanwhile, P1-SO₃Na demonstrated appreciable adsorption capacities, excellent selectivity, effective adsorption of mixed MPs at environmental levels and good reusability. These results confirmed the great potential of P1-SO₃Na as effective adsorbent to remove MPs from water.

Synthesis of porous dimethoxypillar[5]arene knitted β-cyclodextrin copolymers for efficient adsorption of organic micropollutants

Herein, through knitting benzylated β-cyclodextrin (BnCD) by dimethoxypillar[5]arene (P[5]), porous copolymers (P[5]-BnCDs) containing two kinds of macrocycles were synthesized with yields not <97 %. The molar ratio of P[5]/BnCD greatly influenced the P[5]-BnCDs' porosity and adsorption performance. When the molar ratio of P[5]/BnCD was 4/1, the P[5]-BnCD (4-1), demonstrated a surface area up to 515.95 m²/g and showed fast adsorption kinetic, high adsorption capacity and good reusability towards the model organic micropollutants (OMPs). The adsorption fitted well with the pseudo-second-order and the Langmuir models, while the thermodynamic studies revealed spontaneous physisorption process. The adsorption mechanism was dominant by host-guest and hydrophobic interactions and the adsorption at environmentally relevant concentrations experiments showed the practicality and superiority in extraction of the OMPs at μg/L level. This study paves a way for the development of versatile porous organic polymers with multiple macrocycles for efficient removal of OMPs from water.

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.

Piezocatalytic Techniques in Environmental Remediation

As a consequence of rapid industrialization throughout the world, various environmental pollutants have begun to accumulate in water, air, and soil. This endangers the ecological environment of the earth, and environmental remediation has become an immediate priority. Among various environmental remediation techniques, piezocatalytic techniques, which uniquely take advantage of the piezoelectric effect, have attracted much attention. Piezoelectric effects allow pollutant degradation directly, while also enhancing photocatalysis by reducing the recombination of photogenerated carriers. In this Review, we provide a comprehensive summary of recent developments in piezocatalytic techniques for environmental remediation. The origin of the piezoelectric effect as well as classification of piezoelectric materials and their application in environmental remediation are systematically summarized. We also analyze the potential underlying mechanisms. Finally, urgent problems and the future development of piezocatalytic techniques are discussed.

High-Performance Integrated rGO-[Polymeric Ionic Liquid] [Heteropolyanions] for Catalytic Degradation of Azo Dyes

Polymeric ionic liquid (such as poly[ViEtIm]Br)-modified reduced graphene oxide (rGO), rGO-poly[ViEtIm]Br, was nominated as an open carrier to construct a degradation platform. The large specific surface of rGO together with the anion-exchange property of poly[ViEtIm]Br terminals led to the wide growth of heteropolyanions (like [PW₁₂O₄₀]^3-, [PMo₁₂O₄₀]^3-, and [SiW₁₂O₄₀]^4-), thus assembling the integrated catalyst rGO-poly[ViEtIm][heteropolyanions]. The grafted poly[ViEtIm]Br provided an anchor point to interlink the polar heteropolyanions and the nonpolar rGO substrate, endowing this graphene-based catalyst with excellent dispersibility. The adequate exposure of heteropolyanions further promoted the decolorization capability during the degradation procedure. Morphology, structure, and properties of materials were confirmed and monitored via transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, etc. rGO-poly[ViEtIm][PW₁₂O₄₀] was selected as the optimal catalyst with degradation efficiency toward methyl orange reaching 98.7% in 3 h. In addition, the excellent structural stability of the catalyst improved the decolorization efficiency, which reached 95% after recycling five times.

Efficient Recognition and Removal of Persistent Organic Pollutants by a Bifunctional Molecular Material

Persistent organic pollutants (POPs) exist widely in the environment and place significant impact on human health by bioaccumulation. Efficient recognition of POPs and their removal are highly challenging tasks because their specific structures interact often very weakly with the capture materials. Herein, a molecular nanocage (1) is studied as an efficient sensing and sorbent material for POPs, which is demonstrated by a representative and stable perfluorooctane sulfonate (PFOS) substrate containing a hydrophilic sulfonic group and a hydrophobic fluoroalkyl chain. A highly sensitive and unusual turn-on fluorescence response within 10 s and a 97% total removal of PFOS from water in 20 min have been achieved owing to the strong host-guest interactions between 1 and PFOS. The binding constant of 1 to PFOS is 2 orders of magnitude higher than state-of-the-art adsorbents for PFOS and thus represents a new benchmark material for the recognition and removal of PFOS. The host-guest interaction has been elucidated by solid-state NMR spectroscopy and single-crystal X-ray diffraction, which provide key insights at a molecular level for the design of new advanced sensing/sorbent materials for POPs.

Calix[4]pyrrole-Based Azo-Bridged Porous Organic Polymer for Bromine Capture

The toxicity, corrosiveness, and volatility of elemental bromine presents challenges for its safe storage and transportation. Purification from other halogens is also difficult. Here, we report an easy-to-prepare calix[4]pyrrole-based azo-bridged porous organic polymer (C4P-POP) that supports efficient bromine capture. C4P-POP was found to capture bromine as a vapor and from a cyclohexane source phase with maximum uptake capacities of 3.6 and 3.4 g·g^-1, respectively. Flow-through adsorption experiments revealed that C4P-POP removes 80% of the bromine from a 4.0 mM cyclohexane solution at a flow rate of 45 mL·h^-1. C4P-POP also allowed the selective capture of bromine from a 1:1 mixture of bromine and iodine in cyclohexane.

Fabrication of Protonated Two-Dimensional Metal-Organic Framework Nanosheets for Highly Efficient Iodine Capture from Water

Radioactive iodine (¹²⁹I and ¹³¹I), produced or released from nuclear-related activities, posed severe effects on both human health and environment. The efficient removal of radioiodine from aqueous medium and vapor phase is of paramount importance for the sustainable development of nuclear energy. Herein, a metal-organic framework (MOF) nanosheet with a positive charge was constructed for the capture of iodine for the first time. The as-synthesized ultrathin nanosheets, with a thickness of 4.4 ± 0.1 nm, showed a record-high iodine adsorption capacity (3704.08 mg g^-1) from aqueous solution, which is even higher than that from the vapor phase (3510.05 mg g^-1). It can be ascribed to the fully interactions between the extensive accessible active sites on the largely exposed surface of 2D MOF nanosheets and the target pollutants, which also gave rise to fast adsorption kinetics with relative high removal efficiencies in the low concentrations, even in seawater. Moreover, a facile recyclability with fast desorption kinetics can also be achieved for the MOF nanosheets. The excellent iodine removal performance in aqueous solution demonstrated that the electrostatic attraction between MOF nanosheets with a positive charge and the negatively charged triiodide (I₃^-, the dominant form of iodine in aqueous solution) is the driving force in adsorption, which endows the adsorbents with the characteristics of fast adsorption and desorption kinetics. The adsorption mechanism was systematically verified by the studies of ζ potential, Fourier transform infrared, X-ray photoelectron spectroscopy, and Raman spectra.

Encapsulation-Led Adsorption of Neutral Dyes and Complete Photodegradation of Cationic Dyes and Antipsychotic Drugs by Lanthanide-Based Macrocycles

Molecular architectures offering large cavities can accommodate guest molecules, while their compositional engineering allows tunability of the band gap to support photocatalysis using visible light. In this work, two lanthanide (Ln)-based macrocycles, synthesized using a cobalt-based metalloligand and offering large rectangular cavities, exhibited selective adsorption of neutral dyes over both anionic and cationic dyes. Both Ln macrocycles illustrated complete photodegradation of cationic dyes using visible light without the use of any oxidant. Both Ln macrocycles exhibited complete photodegradation of not only cationic dyes but also a few phenothiazine-based antipsychotic drugs. Photocatalysis involved the generation of reactive oxygen species (ROS), which was corroborated with the band gap of two Ln macrocycles. These results were supported by radical scavenger studies and the quantitative estimation of superoxide and hydroxyl radicals. Complete photodegradation of both dyes and drugs was confirmed by spectral studies, while the generation of CO₂ and N₂ gases was established by gas chromatography. Importantly, Ln macrocycles were able to distinguish between the neutral dyes that were quantitatively adsorbed and the cationic dyes/drugs that were completely photodegraded.

Switchable bifunctional molecular recognition in water using a pH-responsive Endo-functionalized cavity

The construction of water-soluble synthetic hosts with a stimuli-responsive endo-functionalized cavity is challenging. These hosts feature a switchable cavity and may bring new properties to the fields of self-assembly, molecular machines, and biomedical sciences. Herein, we report a pair of water-soluble naphthotubes with a pH-responsive endo-functionalized cavity. The inward-directing secondary amine group of the hosts can be protonated and deprotonated. Thus, the hosts have different cavity features at the two states and show drastically different binding preference and selectivity in water. We reveal that the binding difference of the two host states is originated from the differences in charge repulsion, hydrogen bonding and the hydrophobic effects. Moreover, the guest binding can be easily switched in a ternary mixture with two guest molecules by adjusting the pH value of the solution. These pH-responsive hosts may be used for the construction of smart self-assembly systems and water-soluble molecular machines.

Cyclodextrin-enabled green environmental biotechnologies

Most of the organic compounds contaminating the environment can form inclusion complexes with cyclodextrins resulting in enhanced solubility (a benefit in soil remediation) or just the opposite: reduced mobility by sorption (a benefit in wastewater treatment). Combining biotechnologies with cyclodextrin, a renewable and biodegradable material, green environmental technologies of high efficiency were developed. For instance, the cyclodextrin-enabled soil washing/flushing technologies combined with bioremediation have been demonstrated in full-scale field experiments. The efficiency of tertiary wastewater treatment by sorption of non-biodegradable xenobiotics, such as residual pharmaceutics, was proved. The biofilm formation in fouling processes can be prevented or reduced either by applying cyclodextrin-based coatings or by manipulation of quorum sensing (bacterial communication) via capturing signal molecules.

Macrocycle-Based Porous Organic Polymers for Separation, Sensing, and Catalysis

With the rapid development of materials science, porous organic polymers (POPs) have received remarkable attentions because of their unique properties such as the exceptionally high surface area and flexible molecular design. The ability to incorporate specific functions in a precise manner makes POPs promising platforms for a myriad of applications in molecular adsorption, separation, and catalysis. Therefore, many different types of POPs have been rationally designed and synthesized to expand the scope of advanced materials, endowing them with distinct structures and properties. Recently, supramolecular macrocycles with excellent host-guest complexation abilities are emerging as powerful crosslinkers for developing novel POPs with hierarchical structures and improved performance, which can be well-organized at different spatial scales. Macrocycle-based POPs could have unusual porous, adsorptive, and optical properties when compared to their nonmacrocycle-incorporated counterparts. This cooperation provides valuable insights for the molecular-level understanding of skeletal complexity and diversity. Here, the research advances of macrocycle-based POPs are aptly summarized by showing their syntheses, properties, and applications in terms of separation, sensing, and catalysis. Finally, the current challenging issues in this exciting research field are delineated and a comprehensive outlook is offered for their future directions.

Removal of the Micropollutants Propranolol Hydrochloride and 2-Naphthol From Water by Pyridine-Functionalized Polymers

The number and concentration of micropollutants in aqueous environments are increasing. Two such micropollutants include the pharmaceutical, propranolol hydrochloride, and dye intermediate, 2-naphthol. Here, we describe the synthesis of both linear and crosslinked pyridine-functionalized copolymers that bind and remove propranolol hydrochloride and 2-naphthol from water solutions. Propranolol hydrochloride and 2-naphthol both contain hydrogen-bond-donor groups, and the pyridine moiety on the polymer acts as a hydrogen-bond acceptor to facilitate removal. Copolymers with different amounts of pyridine comonomer are synthesized, and as the amount of the pyridine comonomer is increased, the ability of the polymer to bind and remove the contaminant also increases. The concentrations of propranolol hydrochloride and 2-naphthol decreased by approximately 20–40% and 60–88%, respectively, depending on the polymer type that is used in the binding experiment. A control polymer was synthesized by using styrene in place of the pyridine monomer. In analogous binding experiments, the styrene polymer decreases the concentration of propranolol hydrochloride by 2% and 2-naphthol by 26%. Thus, the binding effectiveness is significantly reduced when the hydrogen-bond-acceptor group is not present on the polymer. We also show that the best performing crosslinked pyridine-functionalized polymer is reusable. Overall, these polymer adsorbents demonstrate the potential for removal of micropollutants from water.

Bi-functional water-purification materials derived from natural wood modified TiO2 by photothermal effect and photocatalysis

As one of the sustainable and renewable materials, the carbonization of natural wood is generally considered as a low-cost, environmentally friendly method to fabricate carbon materials. Natural wood, by surficial carbonization, can possess an excellent photothermal effect, low heat loss, and easy water transportation in the solar water desalination process based on the unique structures, leading to high solar water desalination performance. Here, we design and construct a composite of commercial P25 nanocrystal-loaded semi-spherical wood with surficial carbonization at the semi-spherical end (P25/wC-s-s), which is beneficial for light harvesting and water evaporation due to the semi-spherical structure-induced large surface area. The composite displays bi-functions of high solar-to-vapour energy efficiency and an intriguing photo-degradation efficiency for organic pollutants in the solar water purification process. The research provides a novel approach to engineering an efficient, stable, and low-cost bi-functional device for the photothermal/photoelectronic conversion of water treatment.

A bifunctional water-purification material is designed by surficial carbonization of the semi-spherical end of a natural wood block and loading of P25 on the lateral surfaces of wood domains.

Organic pollutants in water-soluble cavitands and capsules: contortions of molecules in nanospace

We report on the binding properties of deep cavitand for various industrial pollutants in water. Depending on the guest type, monomeric cavitands, dimeric capsules or both acted as receptors and...

Reversible Iodine Capture by Nonporous Adaptive Crystals of a Bipyridine Cage

The ability to capture radioactive iodine species is crucial for nuclear accident preparedness and nuclear waste treatment; however, it remains a challenge. Here we report a new readily obtainable nitrogen-rich nonporous cage (BPy-Cage) based on bipyridine building blocks that supports iodine capture. This cage is able to capture not only volatile iodine in vapor form but also iodine dissolved in various organic solvents or aqueous media with an iodine uptake capacity of up to 3.23 g g^-1. The iodine within the cage (I₂@BPy-Cage) can be released quickly upon immersing the bound solid form in DMF, allowing for control over acylation reactions. The cage solids reported here could be reused several times without substantial loss in their iodine capture performance. The effectiveness of the present system is ascribed to its ability to support strong iodine-bipyridine nitrogen lone pair interactions.

Calix[4]pyrrole-based Crosslinked Polymer Networks for Highly Effective Iodine Adsorption from Water

A series of calix[4]pyrrole-based crosslinked polymer networks designed for iodine capture is reported. These materials were prepared by Sonogashira coupling of α,α,α,α-tetra(4-alkynylphenyl)calix[4]pyrrole with bishalide building blocks with different electronic properties and molecular sizes. Despite their low Brunauer-Emmett-Teller surface areas, iodine vapor adsorption capacities of up to 3.38 g g^-1 were seen, a finding ascribed to the presence of a large number of effective sorption sites including macrocyclic π-rich cavities, aryl units, and alkyne groups within the material. One particular system, C[4]P-BTP, was found to be highly effective at iodine capture from water (uptake capacity of 3.24 g g^-1 from a concentrated aqueous KI/I₂ solution at ambient temperature). Fast capture kinetics (k_obs =7.814 g g^-1  min^-1 ) were seen. Flow-through adsorption experiments revealed that C[4]P-BTP is able to remove 93.2 % of iodine from an aqueous source phase at a flow rate of 1 mL min^-1 .

Magnetic Nanoparticle-Embedded Ionic Microporous Polymer Composite as an Efficient Scavenger of Organic Micropollutants

A cationic microporous composite polymer (120-TMA@Fe) bearing free exchangeable chloride anions alongside easy magnetic separation was crafted through post-polymerization structure modulation. The precursor polymer 120-Cl was synthesized via an "external cross-linking" strategy in a straightforward one-pot Friedel-Crafts reaction. Subsequently, a cationic network accommodating magnetic Fe₃O₄ nanoparticles, viz., 120-TMA@Fe was fabricated through chemical modifications. 120-TMA@Fe displayed excellent adsorption proficiency both in terms of rapid kinetics and maximum uptake capacity when screened for a wide range of organic micropollutants of various categories. Amongst the tested pollutants, including anionic dyes, aromatic models, plastic components, and pharmaceuticals, 120-TMA@Fe illustrated exceptional performance in removing all of these model pollutants with adsorption equilibrium reaching within only 5 min. The Langmuir adsorption isotherm model determined the theoretical maximum uptake capacity (q_max,e) of 120-TMA@Fe to be 357 mg g^-1 for methyl orange dye, 555 mg g^-1 for plasticizer bisphenol A, and 285 mg g^-1 for antibiotic ibuprofen. Additionally, 120-TMA@Fe showed unaltered performance upon harsh chemical treatment as well as in complex real-world samples. The potency of 120-TMA@Fe was further supported by its outstanding regeneration performance up to 10 cycles.

Aggregation Mode, Host-Guest Chemistry in Water, and Extraction Capability of an Uncharged, Water-Soluble, Liquid Pillar[5]arene Derivative

An uncharged, water-soluble per-ethylene-glycol pillar[5]arene derivative (1) was synthesized and its aggregation mode, host-guest chemistry in water and extraction ability was explored. Compound 1 is a liquid at room temperature; in water, limited self-aggregation occurred at high concentrations as deduced from diffusion NMR and dynamic light scattering. Compound 1 forms pseudo-rotaxane-like 1 : 1 host-guest complexes with 1,ω-di-substituted alkanes with association constants on the order of 103 -104  m-1 . Interestingly, NMR experiments showed that the guest location relative to the host ring system differs among the different complexes. In proof-of-concept experiments, compound 1 was shown to extract structurally related organic compounds from benzene into water with significant selectivity. Compound 1, which is a liquid at room temperature and has only limited interactions with its side arms, can, in principle, be regarded as a complement to or as a kind of type I porous liquid.

Macrocycle-derived hierarchical porous organic polymers: synthesis and applications

Porous organic polymers (POPs), as a new category of advanced porous materials, have received broad research interests owing to the advantages of light-weight, robust scaffolds, high specific surface areas and good functional tailorability. According to the long-range ordering of polymer skeletons, POPs can be either crystalline or amorphous. Macrocycles with inherent cavities can serve as receptors for recognizing or capturing specific guest molecules through host-guest interactions. Incorporating macrocycles in POP skeletons affords win-win merits, e.g. hierarchical porosity and novel physicochemical properties. In this review, we focus on the recent progress associated with new architectures of macrocycle-based POPs. Herein, these macrocycles are divided into two subclasses: non-planar (crown ether, calixarene, pillararene, cyclodextrin, cyclotricatechylene, etc.) and planar (arylene-ethynylene macrocycles). We summarize the synthetic methods of each macrocyclic POP in terms of the functions of versatile building blocks. Subsequently, we discuss the performance of macrocyclic POPs in environmental remediation, gas adsorption, heterogeneous catalysis, fluorescence sensing and ionic conduction. Although considerable examples are reported, the development of macrocyclic POPs is still in its infancy. Finally, we propose the underlying challenges and opportunities of macrocycle-based POPs.

Ultrahigh Adsorption Capacity and Kinetics of Vertically Oriented Mesoporous Coatings for Removal of Organic Pollutants

Highly efficient removal of organic pollutants currently is a main worldwide concern in water treatment, and highly challenging. Here, vertically oriented mesoporous coatings (MCs) with tunable surface properties and pore sizes have been developed via the single-micelle directing assembly strategy, which show good adsorption performances toward a wide range of organic pollutants. The micelle size and structure can be precisely regulated by oil molecules based on their n-octanol/water partition coefficients (Log P) in the oil-water diphase assembly system, which are critical to the pore size and pore surface property of the MCs. The affinity and steric effects of the MCs can be on-demand adjusted, as a result, the MCs show a ultrahigh adsorption capacity (263 mg g^-1 ), surface occupancy ratio (≈41.92%), and adsorption rate (≈10.85 mg g^-1  min^-1 ) for microcystin-LR, which is among the best performances up to date. The MCs also show an excellent universality to remove organic pollutants with different properties. Moreover, overcoming the challenges proposed by particulate absorbents, the MCs are stable and can be easily regenerated and reused without secondary contamination. This work paves a new route to the synthesis of high-quality MCs for water purification.

Effective and Rapid Removal of Polar Organic Micropollutants from Water by Amide Naphthotube-Crosslinked Polymers

It is challenging to remove polar organic micropollutants from water through adsorption-mediated processes. Macrocycle-crosslinked polymers were recently shown to be effective adsorbents for nonpolar or charged organic micropollutants through specific host-guest binding, but are rarely used for the treatment of neutral and polar organic micropollutants. This is due to the challenge of recognizing polar molecules in water by macrocyclic hosts. In this research, we report two amide naphthotube-crosslinked polymers which can effectively and rapidly adsorb a wide scope of polar organic micropollutants from water through biomimetic molecular recognition. Amide naphthotubes possess hydrogen bonding sites in their deep hydrophobic cavities and can effectively bind polar organic micropollutants in water through the hydrophobic effects and shielded hydrogen bonds. The cross-linked polymers containing amide naphthotubes are even able to remove a complex mixture of organic micropollutants from water and the used materials can be easily regenerated through washing with MeOH or EtOH. This research provides a solution for the treatment of polar organic micropollutants by using biomimetic molecular recognition in water.

A Two-Dimensional Metallacycle Cross-Linked Switchable Polymer for Fast and Highly Efficient Phosphorylated Peptide Enrichment

The selective and efficient capture of phosphopeptides is critical for comprehensive and in-depth phosphoproteome analysis. Here we report a new switchable two-dimensional (2D) supramolecular polymer that serves as an ideal platform for the enrichment of phosphopeptides. A well-defined, positively charged metallacycle incorporated into the polymer endows the resultant polymer with a high affinity for phosphopeptides. Importantly, the stimuli-responsive nature of the polymer facilitates switchable binding affinity of phosphopeptides, thus resulting in an excellent performance in phosphopeptide enrichment and separation from model proteins. The polymer has a high enrichment capacity (165 mg/g) and detection sensitivity (2 fmol), high enrichment recovery (88%), excellent specificity, and rapid enrichment and separation properties. Additionally, we have demonstrated the capture of phosphopeptides from the tryptic digest of real biosamples, thus illustrating the potential of this polymeric material in phosphoproteomic studies.