Porous and flexible membrane derived from ZIF-8-decorated hyphae for outstanding adsorption of Pb2+ ion

Effective enrichment and separation of three flavonoids from Ohwia caudata (Thunberg) H. Ohashi using magnetic layered double hydroxide/ZIF-8 composites and pCEC

In this study, Fe3O4@ZnCr-layered double hydroxide/zeolitic imidazolate frameworks-8 (MLDH/ZIF-8) magnetically functionalized composites were synthesized by co-precipitation and in situ growth based on the advantages of LDHs and ZIF-8 using Fe3O4 nanoparticles as a magnetic substrate to obtain adsorbents with excellent performance. Moreover, the composite was used for the efficient enrichment of flavonoids in Chinese herbal medicines. The internal structures and surface properties were characterized by SEM, Fourier transform infrared spectroscopy, X-ray diffraction and so on. MLDH/ZIF-8 exhibited a large specific surface area and good paramagnetic properties. The MLDH/ZIF-8 magnetic composite was used as a magnetic solid-phase extraction (MSPE) adsorbent, and a MLDH/ZIF-8 MSPE-pressurized capillary electrochromatography coupling method was developed for the separation and detection of flavonoids (luteolin, kaempferol and apigenin) in a sample of the Chinese herb Ohwia caudata (Thunberg) H. Ohashi. The relevant parameters affecting the extraction efficiency were optimized to determine the ideal conditions for MSPE. 5 mg of adsorbent in sample solution at pH 6, vortex extraction for 5 min, elution with 1.5 mL of ethyl acetate for 15 min. The method showed good linearity in the concentration range of 3-50 μg mL-1 with correlation coefficients of 0.9934-0.9981, and displayed a relatively LODs of 0.07-0.09 μg mL-1. The spiked recoveries of all analytes ranged from 84.5% to 122.0% with RSDs (n=3) between 4.5% and 7.7%. This method is straightforward and efficient, with promising potential in the separation and analysis of active ingredients in various Chinese herbal medicines.

Removal of Pb(II) ions by cellulose modified-LaFeO3 sorbents from different biomasses

LaFeO3 perovskite is prepared by the cellulose-modified microwave-assisted citrate method using two different biomasses as a cellulose source; rice straw (RS) and banana peel (BP). The prepared samples are assigned as LaFeO3/cellulose-RS and as LaFeO3/cellulose-BP, respectively. Raman Spectra prove the presence of perovskite and cellulose phases, as well as biochar resulted from the thermal treatment of the cellulose. LaFeO3/cellulose-RS has a cauliflower morphology while, two phases are observed for LaFeO3/cellulose-BP, mesoporous cellulose phase and octahedral LaFeO3 nanoparticles as shown by scanning electron microscope (SEM) images. LaFeO3/cellulose-BP has higher porosity and larger BET surface area than LaFeO3/cellulose-RS. Both samples are applied for the removal of Pb(II) ions from aqueous solution by adsorption. The adsorption follows Langmuir isotherm, with maximum adsorption capacities of 524 and 730 mg/g for LaFeO3/cellulose-RS and LaFeO3/cellulose-BP, respectively. Cellulose precursors from different biomasses affect structural and morphological properties of LaFeO3/cellulose samples as well as the sorption performance for Pb(II) ions. BP is more recommended than RS, as a biomass, in the present study.

A correlation of the adsorption capacity of perovskite/biochar composite with the metal ion characteristics

LaFeO₃/biochar composite is prepared by cellulose-modified microwave-assisted method at 450 °C. The structure is identified by Raman spectrum which, consists of characteristics biochar bands and octahedral perovskite chemical shifts. The morphology is examined by scanning electron microscope (SEM); two phases are observed, rough microporous biochar and orthorhombic perovskite particles. The BET surface area of the composite is 57.63 m²/g. The prepared composite is applied as a sorbent for the removal of Pb²⁺, Cd²⁺, and Cu²⁺ ions from aqueous solutions and wastewater. The adsorption ability reaches a maximum at pH > 6 for Cd²⁺, and Cu²⁺ ions, and is pH-independent for Pb²⁺ ions adsorption. The adsorption follows pseudo 2nd order kinetic model, Langmuir isotherm for Pb²⁺ ions, and Temkin isotherms for Cd²⁺, and Cu²⁺ ions. The maximum adsorption capacities, q_m, are 606, 391, and 112 mg/g for Pb²⁺, Cd²⁺, and Cu²⁺ ions, respectively. The electrostatic interaction is responsible for the adsorption of Cd²⁺, and Cu²⁺ ions on LaFeO₃/biochar composite. In case of Pb²⁺ ions form a complex with the surface functional groups of the adsorbate. LaFeO₃/biochar composite shows high selectivity for the studied metal ions and excellent performance in real samples. The proposed sorbent can be easily regenerated and effectively reused.

Recent advances in MOF-bio-interface: a review

Metal-organic frameworks (MOFs), as a class of promising material with adjustable function and controllable structure, have been widely used in the food industry, chemical industry, biological medicine, and sensors. Biomacromolecules and living systems play a critical role in the world. However, the insufficiency in stability, recyclability, and efficiency, significantly impedes their further utilization in slightly harsh conditions. MOF-bio-interface engineering effectively address the above-mentioned shortages of biomacromolecules and living systems, and thereby attracting considerable attentions. Herein, we systematically review the achievements in the area of MOF-bio-interface. In particular, we summarize the interface between MOFs and proteins (enzymes and non-enzymatic proteins), polysaccharides, DNA, cells, microbes, and viruses. Meanwhile, we discuss the limitations of this approach and propose future research directions. We expect that this review could provide new insights and inspire new research efforts towards life science and material science.

Effective remediation of Pb2+ polluted environment by adsorption onto recyclable hydroxyl bearing covalent organic framework

The removal of heavy metal ions from wastewater has attracted considerable interest because of their toxicity. Adsorption is one of the most promising methods for the removal of heavy metal ions due to its simplicity and effectiveness. Recently, covalent organic frameworks (COFs) have become promising adsorbents for effective wastewater remediation. However, many building blocks have been developed, and the design of COFs with high adsorption efficiency remains a challenge. Here, a covalent organic framework (DHTP-TPB COF) decorated with hydroxyl groups was developed for the efficient removal of Pb²⁺ ions. The DHTP-TPB COF showed excellent performance in adsorbing Pb²⁺ from aqueous solution. More importantly, DHTP-TPB COF exhibited high selectivity for Pb²⁺ compared to other competing ions, capturing Pb²⁺ ions with a removal efficiency of over 96% at pH 4. The results show that the DHTP-TPB COF exhibits excellent adsorption capacity at pH 4 of up to 154.3 mg/g for Pb²⁺ ions; the value is comparable to many previously reported COFs. Moreover, the adsorbed Pb²⁺ ions could be easily eluted with a 0.1 M EDTA solution, and the DHTP-TPB COF can be reused for more than five adsorption-desorption cycles without significant loss of adsorption capacity. Moreover, the adsorption mechanism was revealed using XPS analysis, indicating the formation of strong coordination-bonding interactions between hydroxyl and Pb²⁺ ions. Therefore, the DHTP-TPB COF prepared herein has high potential for the treatment of Pb²⁺-contaminated wastewater and is promising for the adsorption of Pb²⁺ ions in practical applications.

[Advances in enrichment and separation of cis-diol-containing compounds by porous organic frameworks]

The design and synthesis of boronate affinity materials that show high efficiency, high selectivity, and high enrichment performance have gained significant attention. The principle of boronate affinity relies on the reversible covalent reactions, including the formation of stable five-membered or six-membered cyclic esters with cis-diol-containing compounds in alkaline aqueous media and dissociation of cyclic esters in an acidic surrounding to release cis-diol-containing compounds. Recently, various boronate affinity materials have been synthesized and utilized for selective enrichment of these compounds. Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have been widely used in chromatographic separation and sample pretreatment because of their adjustable pore size, high porosity, high specific surface area, tunable skeleton structure, and favorable chemical and thermal stability. To promote the enrichment selectivity of MOFs and COFs for cis-diol-containing compounds, boronic acid-functionalized MOFs and COFs with various structures and categories have been synthesized. This review summarizes more than 80 investigations into the categories, synthetic strategies, and applications of boronic acid-functionalized MOFs and COFs from the Science Citation Index. These synthesis methods include metal ligand-fragment co-assembly, post-synthetic modification, and bottom-up modification of boronic acid-functionalized porous materials. Although two modification strategies (post-synthetic and metal ligand-fragment co-assembly) have been introduced for the preparation of boronic acid-functionalized MOFs, the latter is more commonly adopted as it improves the enrichment selectivity and enrichment efficiency of MOFs. The common limitations of MOFs such as aggregation and aperture issues were also resolved. Boron affinity MOFs possessing favorable properties according to the characteristics of cis-diol-containing compounds, have also been synthesized. Furthermore, to facilitate enrichment and separation, many boronic acid-functionalized magnetic material MOFs have been developed for the enrichment and analysis of cis-diol-containing compounds. Additionally, the luminescent properties of Ln-MOFs have been used in combination with boronic acid affinity for the enrichment, separation, and subsequent detection of cis-diol-containing compounds. Post-synthetic modification and the bottom-up strategy are the primary methods for the preparation of boronic acid-functionalized COFs. Boronic acid-functionalized COFs are less investigated than boronic acid-functionalized MOFs, likely due to the greater complexity of COF synthesis. This work aims to summarize the research advances, synthesis ideas, and synthesis methods related to boric acid-functionalized porous organic frameworks, which will provide theoretical guidance and technical support for its applications while accelerating the commercialization of such organic frameworks.

Research progress of metal organic frameworks and their derivatives for adsorption of anions in water: A review

Anion pollution in water has become a problem that cannot be ignored. The anion concentration should be controlled below the national emission standard to meet the demand for clean water. Among the methods for removing excess anions in water, the adsorption method has a unique removal performance, and the core of the adsorption method is the adsorbent. In recent years, the emerging metal-organic frameworks (MOFs) have the advantages of adjustable porosity, high specific surface area, diverse functions, and easy modification. They are very competitive in the field of adsorption of liquid anions. This article focuses on the adsorption of fluoride, arsenate, chromate, radioactive anions (ReO₄^-, TcO₄^-, SeO₄^2-/SeO₃^2-), phosphate ion, chloride ion, and other anions by MOFs and their derivatives. The preparation methods of MOFs are introduced in turn, the application of different types of metal-based MOFs to adsorb various anions were discussed in categories with their crystal structure and functional groups. The influence on the adsorption of anions is analyzed, including the more common and special adsorption mechanisms, adsorption kinetics and thermodynamics, and regeneration performance are briefly described. Finally, the current situation of MOFs adsorption of anions is summarized, and the outlook for future development is summarized to provide my own opinions for the practical application of MOFs.

Cytotoxicity, oxidative stress, and apoptosis in human embryonic kidney (HEK293) and colon cancer (SW480) cell lines exposed to nanoscale zeolitic imidazolate framework 8 (ZIF-8)

Zinc (zeolitic) imidazolate framework 8 (ZIF-8) has been widely considered in the literature as an ideal candidate for drug delivery especially anti-cancer drugs. However, the available information on the biocompatibility and cytotoxicity of ZIF-8 nanoparticles is contradictory. Therefore, in the present study, the ZIF-8 particles were synthetized, characterized, and their potential toxicity on two eukaryotic cell lines including human embryonic kidney (HEK293) and human colon cancer (SW480) cells was investigated in vitro. The characterization of ZIF-8 particles by TEM, EDX, SEM, and DLS indicated the synthesis of the hexagonal crystals with mean diameter of 124.71±32.74 nm and the presence of the zinc element at 86.25% by weight (wt%) of the ZIF-8 structure. The results of the cytotoxicity assessment of ZIF-8 NPs showed that the viability of two different cell lines reduced significantly coincident with increasing exposure concentration from 0 to 500 μg mL^-1 (P<0.05). The 24-h half-inhibitory concentration (IC50-24 h) values of ZIF-8 NPs for HEK293 and SW480 cell lines were 116.22 and 36.23 μg mL^-1, respectively. We found that the viability of SW480 cells was significantly lower than the HEK293 cells in all exposure concentrations of ZIF-8 NPs except control. Exposure of both cells resulted in increasing of the intracellular reactive oxygen species (ROS) production and activation of apoptosis pathway. The apoptosis rate of cancer SW480 cells was higher than the normal HEK293 cells. These findings indicate that synthetized ZIF-8 NPs could be a candidate for cancer therapy, although their toxic effects on the normal cells also should be considered.

Enhanced removal of Co(II) and Ni(II) from high-salinity aqueous solution using reductive self-assembly of three-dimensional magnetic fungal hyphal/graphene oxide nanofibers

Layer-structured graphene oxide excellent carrier for modifications; however, its poor recoverability and stability preclude its application in wastewater treatment fields. Herein, three-dimensional magnetic fungal hyphal/graphene oxide nanofibers (MFHGs) were assembled by a reductive self-assembly (RSA) strategy for the efficient capture of Co(II) and Ni(II) from high-salinity aqueous solution. The RSA strategy is inexpensive, eco-friendly and easy to scale up. The obtained MFHGs enhanced the dispersity and stability of graphene oxide and exhibited excellent magnetization and large coercivity, leading to satisfactory solid-liquid separation performance and denser sediment. The results of batch removal experiments showed that the maximum removal capacity of MFHGs for Ni(II) and Co(II) was 97.44 and 104.34 mg/g, respectively, in 2 g/L Na₂SO₄ aqueous solution with a pH of 6.0 at 323 K, and the effects of initial pH and ionic strength on Co(II) and Ni(II) removal were explored. Yield residue analysis indicated that the high porosity and oxygen-containing functional groups of MFHGs remarkably improved their Co(II)- and Ni(II)-removal capacities. According to the analysis, hydroxyl groups and amine groups participated in the chemical reaction of Co(II) and Ni(II) removal, and cation-exchange chemical adsorption was dominant during the Co(II)- and Ni(II)-removal process. Based on the attributes of MFHGs, a continuous-flow recycle reactor (CFRR) was proposed for emergency aqueous solution treatment and exhibited satisfactory removal efficiency and regeneration performance. The combination of MFHGs and the proposed CFRR is a promising water treatment strategy for rapid treatment applications.