Ionic Covalent Organic Framework Research Articles

Fabrication of a multifunctional ionic covalent organic framework via the Menshutkin reaction and ion-exchange for dual-mode detection of organochlorine pesticides and design of a smartphone sensing platform

A novel ionic COF has been successfully synthesized through a two-step process, which can be used for dual-mode detection of organochlorine pesticides and the construction of a smartphone sensing platform.

A nanotrap infused ultrathin hybrid composite material for rapid and highly selective entrapment of 99TcO4.

99Tc is one of the potentially toxic radioactive substances owing to its long half-life and a high degree of environmental mobility. Hence, the sequestration of 99Tc from radioactive waste has become enormously important and a contemporary research priority. However, selective extraction of this species in its stable oxoanionic form (99TcO4 -) is very challenging on account of bottlenecks such as low charge density, less hydrophilic nature, etc. Herein, an ultrathin hybrid composite material has been strategically designed and fabricated by covalent anchoring of a chemically stable amino functionalized nanosized cationic metal-organic polyhedron with a positively charged robust ionic covalent organic framework. The resulting thin-layer-based hybrid composite presented multiple exfoliated exposed interactive sites, including a Zr(iv)-secondary building unit, amine and triaminoguanidine functional groups, which can selectively interact with TcO4 - oxoanions through a synergistic combination of electrostatic, H-bonding and various other supramolecular interactions. Thus synthesized function-tailored composite, by virtue of its multiple unique characteristics, manifested an ultrafast and very selective, high distribution coefficient (∼106 mL g-1), as well as recyclable entrapment of TcO4 - oxoanions from the complex mixture of superfluous (∼5000-fold) other interfering anions in both high and ultra-trace concentrations along with simulated nuclear waste and from different water systems. Dynamic flow-through experiments were conducted with the membrane of the hybrid material in simulated wastewater, which reduced the concentration of ReO4 - (surrogate of radioactive TcO4 -) to below the WHO permissible level with rapid sequestration kinetics and excellent selectivity over excessive competing anions.

Construction of cationic covalent organic framework for efficient gold extraction.

In this work, we report a rare ionic covalent organic framework (named as ECUT-iCOF-5) synthesized by the Knoevenagel reaction using an ionic liquid monomer. ECUT-iCOF-5 is found to show a promising potential for gold extraction with a high extraction ability towards gold, including a high extraction capacity (3260 mg g-1), good selectivity over both cations and anions, and good recycle use (at least six times).

Exploring metal-free ionic covalent organic framework nanosheets as efficient OER electrocatalysts via cationic-π interactions

Metal-free electrocatalysts play a crucial role in enabling practical water splitting for future clean energy production by facilitating the oxygen evolution reaction (OER). However, the preparation of such electrocatalysts presents significant challenges due to the limitations of the kinetically sluggish anodic half-cell reaction, which restricts the attainment of high energy inputs. In this study, we present a metal- and pyrolysis-free ionic covalent organic framework (COF) nanosheet, denoted as JUC-627-NS, and investigate its potential as an efficient electrocatalyst for OER by introducing cationic-π interactions. Notably, through the utilization of positively charged JUC-627-NS as cationic donors and π-conjugated graphene as electron donors for the first time, the JUC-627-NS@G-2 composite exhibits an exceptional ultralow overpotential of 275 mV at a current density of 10 mA cm−2, ranking among the top-performing metal- and pyrolysis-free electrocatalysts reported thus far. Combining theoretical calculations with in-situ infrared spectroscopy, we validate that the imidazolium salt moiety of JUC-627-NS serves as the active center of the electrocatalyst, while the robust cation-π interaction within the complex brings the reaction site closer to graphene, acting as a conductive agent. These findings highlight a novel strategy for advancing the development of metal-free OER electrocatalysts based on ionic COF materials, with promising applications in energy conversion and storage devices.

Multivariate surface self-assembly strategy to fabricate ionic covalent organic framework surface grafting monolithic sorbent for enrichment of aristolochic acids prior to high performance liquid chromatography analysis

Herein, an ionic covalent organic framework (iCOF) surface grafting monolithic sorbent was prepared by the multivariate surface self-assembly strategy for in-tube solid-phase microextraction (SPME) of trace aristolochic acids (AAs) in serum, traditional Chinese medicines (TCMs) and Chinese patent drug. Via adjusting the proportion of ionic COF building block during the self-assembly, the density of quaternary ammonium ions in the iCOF was modulated for the enhanced adsorption of AAs. The successful preparation of iCOF surface grafting monolithic sorbent was confirmed by different means. A multiple mode mechanism involving π-π stacking, hydrophobic, electrostatic and hydrogen-bonding interactions was primarily attributed to the adsorption. Several in-tube SPME operating conditions, such as the dosage of ionic COF building block, ACN percentage and TFA percentage in the sampling solution, ACN percentage and TFA percentage in eluent and the collection time span, were optimized to develop the online in-tube SPME-HPLC method for analysis of AAs. Under the optimized conditions, a good linearity was obtained in the concentration range of 20–1000 ng/mL for target AAs in serum samples, the limits of detection (LODs) were less than 10 ng/mL, while the recoveries ranged from 90.3 % to 98.7 % with RSDs (n = 5) below 7.9 %. This study developed a feasible approach to iCOF functionalized monolithic sorbent for SPME and further exhibited the vast potential for the application of COF based monolithic sorbent in sample preparation.

Oriented ionic covalent organic framework membranes for efficient organic solvent nanofiltration

Developing effective organic solvent nanofiltration (OSN) membranes to separate molecular solutes from organic solvents is highly desired yet requires a suitable material platform and an in-depth investigation of membrane selectivity. Herein, an oriented ionic covalent organic framework membrane (oi-COM) was fabricated, which features well-ordered channels that are vertically aligned towards the membrane surface and lined with abundant sulfonate groups. Filtration experiments of multifarious organic solvents and solutes with different charges and molecular sizes were conducted. The oi-COM exhibited above 99% rejection for negatively charged dye (Evans blue), much higher than that for positively charged dye with similar molecular size, while maintaining high solvent permeance for ethanol of 63 L m−2 h−1 bar−1. These results demonstrated the significance of electrostatic repulsion effect in membrane selectivity, providing insights for the design of high-performance OSN membranes.

Incorporating graphene oxide into COF membranes enables ultrahigh proton conductivity and ultralow H2 crossover

Proton exchange membranes (PEMs) are the core components of electrochemical hydrogen energy production, storage and conversion devices. It is a great challenge to develop PEMs with a combination of high proton conductivity, minimal H2 crossover and mechanical robustness for achieving high efficiency and long-term stability in these devices. Here, a co-assembled PEM composed of ionic covalent organic framework (iCOF) nanosheets and functionalized graphene oxide (GO) nanosheets was presented. The iCOF (TpPa-SO3H) nanosheets and polydopamine-modified graphene oxide (DGO) nanosheets were co-assembled into TpPa-SO3H/DGO mixed nanosheets with ultrahigh aspect ratio, which were readily further processed into TpPa-SO3H/DGO co-assembled membranes. The abundant and uniformly distributed –SO3H groups on TpPa-SO3H nanosheets and the acid-base pairs formed between TpPa-SO3H and DGO nanosheets promoted proton conduction significantly. Additionally, the dense structured DGO nanosheets inhibited H2 crossover remarkably, and the multiple interactions between TpPa-SO3H and DGO nanosheets enhanced mechanical strength. The resultant TpPa-SO3H/DGO co-assembled membrane exhibited an ultrahigh proton conductivity of 916.4 mS cm−1 (80 °C, 100% RH), an unprecedently low H2 crossover of 9.7 barrer and a sufficient tensile stress of 87.8 MPa. The enhanced proton conduction and H2 barrier property led to enhanced performance in both electrochemical hydrogen compression and single hydrogen fuel cells.

3D covalent organic framework membrane with fast and selective ion transport

3D ionic covalent organic framework (COF) membranes, which are envisioned to be able to break the trade-off between ion conductivity and ion selectivity, are waiting for exploitation. Herein, we report the fabrication of a 3D sulfonic acid-functionalized COF membrane (3D SCOF) for efficient and selective ion transport, using dual acid-mediated interfacial polymerization strategy. The 3D SCOF membranes possess highly interconnected ion transport channels, ultramicroporous pore sizes (0.97 nm), and abundant sulfonate groups (with a high ion exchange capacity of 4.1 mmol g−1), leading to high proton conductivity of 843 mS cm−1 at 90 °C. When utilized in osmotic energy conversion, a high power density of 21.2 W m−2, and a remarkable selectivity of 0.976 and thus an exceptional energy conversion efficiency of 45.3% are simultaneously achieved. This work provides an alternative approach to 3D ionic COF membranes and promotes the applications of 3D COFs in ion transport and separation.

Achieving multi-dimensional Li+ transport nanochannels via spatial-partitioning in crystalline ionic covalent organic frameworks for highly stable lithium metal anode

The fragile solid electrolyte interphase (SEI) and anisotropic dendrite growth during Li plating/stripping have posed as intractable handicaps to the practical implementation of lithium metal batteries (LMBs). The Li+ uniform distribution and unimpeded transfer play significant roles to enable protuberance-free Li textures. Herein, the highly-crystalline TFSI− ionic-covalent organic framework (I-COF) endowed with designated mixed-dimensional channels was constructed as an artificial SEI layer via anionic post-modification. Benefiting from the desirable spatial-partitioning effect triggered by nanochannels reconfiguration, the I-COF with expanded multi-dimensional Li+ transport channels and scaled-down pore volume could effectively disperse the local concentration gradient of Li+ flux and inhibit growth of Li dendrites. Besides, the coordinated TFSI− anions with a high tLi+ of 0.76 can selectively restrict the delivery and decomposition of homogeneous ions. To understand the interfacial charge transfer mechanisms, the lithophilic properties and the energy barriers for Li+ migration were also calculated. Correspondingly, the I-COF(TI−) modified Li|Li symmetric cell showed superb durability over 5500 h at 4 mA cm−2 with extraordinary overpotential. The Li|S full cell also displayed prolonged lifespan and excellent rate performance. The comprehension of the mixed-dimensional interfacial strategy via spatial-partitioning provides new insights into the fabrication of solid–solid interfaces, which can aid in the improved design and development of advanced lithium-metal batteries (LMBs).

Guanidinium-functionalized ionic covalent organic framework for selective and efficient recovery of palladium(II) from metallurgical wastewater

Efficient and selective recovery of palladium from acidic metallurgical wastewater is of great economic and environmental importance but remains challenging. Here, two novel ionic covalent organic frameworks (iCOFs), Tp-DGCl and BT-DGCl, were synthesized by reaction of 1,3-diaminoguanidine hydrochloride with 1,3,5-triformyphloroglucinol and benzene-1,3,5-triscarbaldehyde, respectively, and then applied to the recovery of Pd(II) from metallurgical wastewater. The maximum adsorption capacities of Tp-DGCl and BT-DGCl at pH 2.0 and 298.15 K were 342.1 mg g−1 and 231.1 mg g−1, which are higher than the majority of similar reported adsorbents. The adsorption isotherms of Pd(II) on iCOFs were highly consistent with the Langmuir isotherm model. Furthermore, the kinetics of the adsorptions by Tp-DGCl and BT-DGCl conformed to the quasi-second-order kinetic model, indicating that the controlling step of adsorption is chemical adsorption. Thermodynamic studies revealed that elevated temperatures are beneficial for the recovery of Pd(II). At the same time, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential, and density functional theory computational analysis confirmed that electrostatic attraction and coordination are the main mechanisms for Pd(II) adsorption on iCOFs. This work not only highlights that the prepared iCOFs can be used as effective reusable adsorbents to selectively adsorb Pd(II) but also opens the door for the practical application of iCOFs in recovering palladium from complex metallurgical wastewater.

An ultrastable cationic covalent organic framework for selective capture of silver from aqueous solution

Recovery of silver from wastewater is a promising alternative from the economic and environmental perspective. Herein, we present an ultrastable ionic covalent organic framework (COF) as a recyclable adsorbent for Ag(I) recovery. The COF exhibits a large surface area, regular pores, and extremely high chemical stability combined with the confined ionic interface, which makes it an excellent material for silver adsorption with fast adsorption kinetics, excellent selectivity, and high saturated adsorption capacity (up to 349.6 mg/g). The superb uptake performance of the cationic COF is attributed to the in-situ precipitation of AgBr and adsorption as well as the coordination of O atoms on the framework to silver.

Europium chelate-anionic exchange functionalized covalent organic frameworks for the sensing of aristolochic acid a in humans and sulfamethoxazole/trimethoprim in surface water

The application of covalent organic frameworks (COFs) in fluorescence detection is of great interest. Herein, we have synthesized the ionic covalent organic framework TGH+·PD: Eu(TTA)4 with the characteristic emission of lanthanides by a straightforward ion-exchange method. This is the first time that aristolochic acid A (AA), a key biomarker for absorption and metabolism in the body for early diagnosis of diseases, has been detected by using COF as a fluorescent probe, which exhibits a good linear correlation with the AA concentration over a range from 5.0 to 1000 μM with a detection limit of 0.0808 μM. In addition, the selective response to sulfamethoxazole (SMZ)/trimethoprim (TMP) is achieved by varying the excitation wavelength with detection lines of 30.2 nM and 2.898 μM, respectively. It is worth mentioning that BNPP has been developed for the accurate determination of SMZ in uncertain samples. In a word, the prepared TGH+·PD: Eu(TTA)4-based sensor can be used for the quantitative detection of AA and SMZ/TMP, separately, effectively extending the application of COFs in the field of fluorescence sensing.

Water/Vapor Assisted Fabrication of Large-Area Superprotonic Conductive Covalent Organic Framework Membranes.

Fabrication of large-area ionic covalent organic framework membranes (iCOMs) remains a grand challenge. Herein, the authors report the liquid water and water vapor-assisted fabrication of large-area superprotonic conductive iCOMs. A mixed monomer solution containing 1,3,5-triformylphloroglucinol (TFP) in 1,4-dioxane and p-diaminobenzenesulfonic acid (DABA) in water is first polymerized to obtain a pristine membrane which subsequently underwent crystallization process in mixed vapors containing water vapor. During the polymerization stage, water played a role of a diluting agent, weakening the Coulombic repulsion between sulfonic acid groups. During the crystallization stage, water vapor played a role of a structure-directing agent to facilitate the formation of highly crystalline, large-area iCOMs. The resulting membranes achieved a proton conductivity value of 0.76 S cm-1 at 90 °C under 100% relative humidity, which is among the highest ever reported. Using liquid water and water vapor as versatile additives open a novel avenue to the fabrication of large-area membranes from covalent organic frameworks and other kinds of crystalline organic framework materials.

Magnetic Resonance Diagnosis of Early Triple-Negative Breast Cancer Based on the Ionic Covalent Organic Framework with High Relaxivity and Long Retention Time.

Patients with triple-negative breast cancer (TNBC) have dismal prognoses due to the lack of therapeutic targets and susceptibility to lymph node (LN) metastasis. Therefore, it is essential to develop more effective approaches to identify early TNBC tissues and LNs. In this work, a magnetic resonance imaging (MRI) contrast agent (Mn-iCOF) was constructed based on the Mn(II)-chelated ionic covalent organic framework (iCOF). Because of the porous structure and hydrophilicity, the Mn-iCOF has a high longitudinal relaxivity (r1) of 8.02 mM-1 s-1 at 3.0 T. For the tumor-bearing mice, a lower dose (0.02 mmol [Mn]/kg) of Mn-iCOF demonstrated a higher signal-to-noise ratio (SNR) value (1.8) and longer retention time (2 h) compared to a 10-fold dose of commercial Gd-DOTA (0.2 mmol [Gd]/kg). Moreover, the Mn-iCOF can provide continuous and significant MR contrast for the popliteal LNs within 24 h, allowing for accurate evaluation and dissection of LNs. These excellent MRI properties of the Mn-iCOF may open new avenues for designing more biocompatible MRI contrast agents with higher resolutions, particularly in the diagnosis of TNBC.

Leaf-like ionic covalent organic framework for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs: Adsorption performance and mechanism insights

In recent years, ionic covalent organic frameworks (iCOFs) have become popular for the removal of contaminants from water. Herein, we employed 2-hydroxybenzene-1,3,5-tricarbaldehyde (TFP) and 1,3-diaminoguanidine monohydrochloride (DgCl) to develop a novel leaf-like iCOF (TFP-DgCl) for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs (NSAIDs). The uniformly distributed adsorption sites, suitable pore sizes, and functional groups (hydroxyl groups, guanidinium groups, and aromatic groups) of the TFP-DgCl endowed it with powerful and selective adsorption capacities for NSAIDs. Remarkably, the optimal leaf-like TFP-DgCl demonstrated an excellent maximum adsorption capacity (1100.08 mg/g) for diclofenac sodium (DCF), to the best of our knowledge, the largest adsorption capacity ever achieved for DCF. Further testing under varying environmental conditions such as pH, different types of anions, and multi-component systems confirmed the practical suitability of the TFP-DgCl. Moreover, the prepared TFP-DgCl exhibited exceptional reusability and stability through six adsorption–desorption cycles. Finally, the adsorption mechanisms of NSAIDs on leaf-like TFP-DgCl were confirmed as electrostatic interactions, hydrogen bonding, and π-π interactions. This work significantly supplements to our understanding of iCOFs and provides new insights into the removal of NSAIDs from wastewater.

Ionic Dye Based Covalent Organic Frameworks for Photothermal Water Evaporation

AbstractConversion of solar energy into heat for water evaporation is of great significance to provide clean and sustainable technology for water purification by using inexhaustible sunlight. In this field, one of the challenges comes from the design of high‐performance photothermal materials powerful in light harvesting, light‐to‐heat conversion, and water activation. Herein, it is demonstrated that rationalization of the ionic covalent organic framework (iCOF) can simultaneously satisfy these multiple requirements and a new iCOF STTP is constructed through the Schiff base chemistry in a rapid microwave‐assisted solvothermal route by using a hydrophilic dye molecule safranineT as the ionic building block. The integrated dye‐related ionic moieties greatly strengthen the light absorbance (>97%) throughout the entire solar spectrum from UV–vis to the infrared region. The framework ionic moieties provide strong polarization to reduce the exciton dissociation energy for enhanced photothermal effect, and in addition, promote sufficient water activation to decrease the water evaporation enthalpy. As an outcome, the STTP driven solar water evaporator affords a fast water evaporation rate of 3.55 kg h−1 m−2 and high solar‐to‐vapor efficiency of 95.8%. This study highlights the potential of designing iCOF materials for photothermal applications.

Solid-state synthesis of intrinsically proton-conducting covalent organic framework membrane

Ionic covalent organic framework (iCOF) membranes are attractive for a myriad of applications. Here, we report a mechanochemistry-based solid-state synthesis method to fabricate iCOF membranes with simplicity, scalability and sustainability. Time-dependent experiments reveal that the iCOF membrane formation process includes the structural transformation from disorder to order and the morphology change to the dense structure formed by the restacking of nanosheet-like crystallites simultaneously. The obtained free-standing iCOF membranes demonstrate high ion exchange capacity, mechanical strength and comparable proton conductivity, benefiting from the rigid crystalline framework structure and one-dimensional channels decorated with abundant proton-conducting sites. This work paves the way for synthesis of iCOF membranes in a simple and environmentally friendly manner.

Spacer-Engineered Ionic Channels in Covalent Organic Framework Membranes toward Ultrafast Proton Transport.

Side-chain engineering of covalent organic frameworks as advanced ion conductors is a critical issue to be explored. Herein, ionic covalent organic framework membranes (iCOFMs) with spacer-engineered ionic channel are de novo designed and prepared. The ionic channels are decorated with side chains comprising spacers having different carbon chain lengths and the -SO3 H groups at the end. Attributed to the synergistic contribution from the spacers and the -SO3 H groups, the iCOFM with moderate-length spacer exhibit the highest through-plane proton conductivity of 889 mS cm-1 at 90°C.

Gold recovery from E-waste using freestanding nanopapers of cellulose and ionic covalent organic frameworks

The ever-increasing production of electronic devices generates a huge amount of electronic waste (E-waste). Therefore, there is an urgent need for advanced recycling technology for E-waste that provides both economic and environmental benefits. Herein, we describe the preparation of flexible, freestanding CF-COF nanopapers consisting of cellulose fibers (CFs) and guanidinium-based ionic covalent organic framework (COF) that can be used for recovering gold from E-waste leaching solutions via a membrane separation technique. Due to the synergetic effects of physical adsorption, ion exchange and chemical reduction, the COF has an extremely high capture capacity (up to 1,794 mg of Au per gram of COF), is highly selective and has fast kinetics for adsorbing trace amounts of [AuCl4]− in aqueous solution. The high COF loadings (∼50 wt%) and hierarchical porosity of the CF-COF nanopapers resulted in excellent performance when capturing gold species from the E-waste leaching solution. This study provides new possibilities for developing sustainable membrane materials, and highly efficient and cost-effective techniques for the recovery of precious metals from E-waste.

Rapid and selective removal of toxic and radioactive anionic pollutants using an ionic covalent organic framework (iCOF-2)

The schematic representation of iCOF-2 as an effective adsorbent for trapping of toxic and radioactive species from aqueous solutions.