Hydrolytically stable citrate capped Fe3O4@UiO-66-NH2 MOF: A hetero-structure composite with enhanced activity towards Cr (VI) adsorption and photocatalytic H2 evolution

Construction of direct Z-scheme Co9S8/CdS with tubular heterostructure through the simultaneous immobilization and in-situ reduction strategy for enhanced photocatalytic Cr(VI) reduction under visible light

Tubular Co9S8/CdS heterostructures have been successfully synthesized by in-situ growing CdS onto Co9S8 nanotubes through a simultaneous immobilization and in-situ reduction strategy. It turned out that the so-obtained heterostructure with Co9S8/CdS molar ratio of 1/10 can display a broad light absorption edge and especially much enhanced capacity for photocatalytic reduction of Cr(VI) under visible light. The characterization analysis and experimental results suggested that an interfacial electrostatic field between Co9S8 and CdS elements in the heterostructure could be constructed due to their different Fermi levels, allowing for more quantities of highly reductive electrons to participate in the photocatalytic reaction. Therefore, the so-obtained Co9S8/CdS (1/10) heterostructures could achieve the photocatalytic reduction efficiency of 100% within 20 min, which was more than two and four times larger than that of pristine CdS and Co9S8, respectively. Moreover, the possible photocatalytic reaction mechanism for reducing Cr(VI) was investigated and found to follow the direct Z-scheme charge transfer pathway. This novel fabrication route for composite photocatalysts with tubular heterostructures could lead to the widespread implementations for the elimination of various harmful pollutants in the process of environmental governance.

Pore Characteristics and Dye Adsorption Mechanism of Functionalized UiO-66s with Various Ratios of Amino Groups

A series of UiO-66 samples with various amino functional group ratios were prepared by modulating the proportion of terephthalic acid (H2BDC) and aminoterephthalic acid (H2BDC-NH2) ligands, and the microstructure of the samples and dependence of methyl orange (MO) adsorption properties on the amino group content were investigated by X-ray diffraction, scanning electron microscopy, FTIR spectra, nitrogen adsorption, positron annihilation lifetime spectroscopy, and UV-vis spectra. The results showed that as the ratio of amino groups increased, the specific surface area and total porosity of the samples decreased, primarily due to decrement in the crystallinity as well as the bulky effect of amino groups in inherent pores. Interestingly, the amino-functionalized samples possessed considerable adsorption capacity of MO even in alkaline conditions due to the hydrogen bonding between the MO and -NH2 groups. The adsorption kinetics, isotherms, and thermodynamics revealed that MOs' adsorption process in amino-functionalized UiO-66s was exothermic, obeying a Langmuir-type adsorption dominated by chemisorption. UiO-66-NH2-0.4 (H2BDC:H2BDC-NH2 = 2:3) exhibited the best adsorption performance, with a maximum adsorption capacity of 336.7 mg/g, and the adsorption capacity was slightly decreased with increasing salt concentration in solution. UiO-66-NH2-0.4 could be easily regenerated by washing with a mixed solution of ethanol and water. The results demonstrated that although amino groups led to relatively less crystallinity and lower micropore volumes, the strong electrostatic attraction and hydrogen bonding between amino groups and MOs enhanced the adsorption capacity of MOs in amino-functionalized UiO-66s, in which MOs were adsorbed in two types of inherent pores, as shown by a significant decrement in positronium annihilation in them upon MO adsorption.

Recent advances in manipulating strategies of NH2-functionalized metallic organic frameworks-based heterojunction photocatalysts for the sustainable mitigation of various pollutants

NH2-functionalized metal-organic frameworks (NH2-functionalized MOFs) can abate organic pollutants, predominantly favored by their chemical, mechanical, and thermal stabilities. The present review stated the chemistry of identifying NH2-functionalization and its role in enhancing the properties of bare MOFs. The integration of the amine group bestows several advantages: 1.) enabling band structure modification, 2.) establishing strong metal-NH2 bonds, 3.) preserving MOF structures from reactive oxygen species, and 4.) shielding MOF structures against pH alterations. Consequently, the NH2-functionalized MOFs are promising materials for the photodegradation of organic contaminants. The following section illustrates the two approaches (pre-synthetic and post-synthetic) for NH2-functionalized MOFs. Nevertheless, specific intrinsic limitations, entailing a high recombination rate of charge carriers and inadequate optical adsorption, restrain the applicability of NH2-functionalized MOFs. Accordingly, the succeeding segment presents strategies to elevate the photocatalytic activities of NH2-functionalized MOFs via heterojunction fabrication. The importance of the NH2-functionalized MOFs-based heterojunction has been evaluated in terms of the effect on the enhancement of charge separation, optical adsorption, and redox ability of charge carriers. Subsequently, the potential application for organic pollutant degradation via NH2-functionalized MOFs-based heterojunctions has been scrutinized, wherein the organic pollutants. Eventually, the review concluded with challenges and potential opportunities in engaging and burgeoning domains of the NH2-functionalized MOFs-based heterojunctions.

Interaction characteristics and mechanism of Cr(VI)/Cr(III) with microplastics: Influence factor experiment and DFT calculation

The coexistence of highly toxic heavy metal chromium and new pollutants microplastics has been widely present, and the interaction behavior and mechanism of the two are crucial for their environmental effects in coexisting environments, which urgently need to be further explored. Firstly, the interaction characteristics of polyamide (PA) and polyethylene (PE) with Cr(VI)/Cr(III) were investigated, where PA exhibited higher adsorption capacity of both Cr(VI) and Cr(III) than PE among various environmental conditions. The higher adsorption energy of PA on Cr(VI)/Cr(III) was also achieved by DFT calculation, and the bending configuration of PA during the adsorption process may be beneficial for its interaction with Cr. Then, the combination of characterization analysis and DFT calculation showed that significant chemical bonding occurred in the interaction between CO bond of PA and Cr(III), weak chemical interactions occurred in the adsorption of PE with Cr(III) and PA with Cr(VI), while the adsorption of PE with Cr(VI) was mainly physical effects. This study provides theoretical support for pollution control of microplastics and chromium in co-existing environment.

Novel Ag@NH2-UiO-66(Zr) photocatalyst with controllable charge transfer pathways for efficient Cr(VI) remediation

Rational fabrication of core-shell photocatalysts to hamper the charge recombination is extraordinarily essential to enhance photocatalytic activity. In this work, core-shell Ag@NH2-UiO-66 (Ag@NU) Schottky heterojunctions with low Ag content (1 wt%) were constructed by a two-step solvothermal method and adopted for Cr(VI) reduction under LED light. Typically, the one with the Ag: NH2-UiO-66 mass ratio (1 : 100) led to 100% Cr(VI) removal within 1 h, superior to bare NH2-UiO-66 and Ag/NH2-UiO-66 (Ag was directly decorated on NH2-UiO-66 surface). The enhanced photocatalytic activity was related to the migration of the electrons on the CB of NH2-UiO-66 to Ag NPs through a Schottky barrier, and thus the undesired charge carriers recombination was avoided. This result was also evidenced by Density functional theory (DFT) calculations. The computational simulations indicate that the introduction of Ag effectively narrowed the band gap of NH2-UiO-66, facilitating the transfer of photo-generated electrons, expanding the light absorption area, and significantly enhancing photocatalytic efficiency. Most importantly, such a core-shell structure can inhibit the formation of •O2-, letting the direct Cr(VI) reduction by photo-excited e-. In addition, this structure can also protect Ag from being oxidized by O2. Ten cyclic tests evidenced the Ag@NU had excellent chemical and structural stability. This research offers a novel strategy for regulating the Cr(VI) reduction by establishing core-shell photocatalytic materials.

In situ synthesis of porous metal-organic frameworks NH2-UiO-66 on tea stem biochar and application in odours adsorption

Multiple odour nuisance in livestock farming is a notorious problem that has a significant impact on the living environment of surrounding communities. Adsorbents based on metal-organic framework (MOF) materials show great promise for controlling odour pollution, as they offer a high specific surface area, a controllable structure and an abundance of active sites. However, the MOF formation process is prone to problems such as pore clogging or collapse and reduced porosity, which limits its further application. In this study, a series of odour adsorbents were prepared by in situ growth of NH2-UiO-66 on tea stem biochar (TSBC) using a hydrothermal method and named UiO (Zr)-TSBCx. The physical and chemical properties and composition of UiO (Zr)-TSBCx have been systematically characterized using SEM, TEM, XRD, FT-IR, N2 adsorption-desorption and XPS. The release of odours from the pig farm effluent was monitored using in-situ continuous Proton-Transfer-Reaction Mass Spectrometry (PTR-MS), and the obtained primary compositions were tested for further adsorption. In dynamic adsorption experiments focused on butyric acid, UiO (Zr)-TSBC2 showed a high adsorption capacity of 3.99 × 105 μg/g and exceptional structural stability. UiO (Zr)-TSBC2 showed variable adsorption efficiencies for different odorous gases, with the best performance for the removal of ammonia, toluene and butyric acid. It also demonstrated the ability to rapidly mitigate instantaneous high concentrations of hydrogen sulfide (H2S), methanethiol and toluene resulting from agitation. Additionally, based on the relationship between the adsorption amount and the structural characteristics of the adsorbent as well as the nature of the odours, a possible adsorption mechanism of UiO (Zr)-TSBC2 for a variety of odours released from pig farm effluent was proposed. This work demonstrates a novel approach to promote deodorization applications in livestock and poultry farming environments by the in-situ growth of NH2-UiO-66 on biochar prepared from tea stem.

Direct Z-scheme system of UiO-66 cubes wrapped with Zn0.5Cd0.5S nanoparticles for photocatalytic hydrogen generation synchronized with organic pollutant degradation

Optimized fabrication of Z-scheme photocatalyst based on MOF materials offers sustainable energy generation and environmental improvement due to their attractive properties. The Z-scheme heterojunctions consisting of UiO-66 cubes covered with Zn0.5Cd0.5S nanoparticles were fabricated by a facile solvothermal method. Thanks to the Z-scheme carrier transport under simulated sunlight irradiation, UiO-66@Zn0.5Cd0.5S exhibited enhanced photocatalytic performance of H2 generation synchronized with organic pollutant degradation in fluoroquinolone antibiotic wastewater. Synergistically, the highest comprehensive performance was obtained in ciprofloxacin solution. The H2 yield reached 224 μmol∙ g-1∙ h-1 and simultaneously the removal efficiency was up to 83.6 %. The degradation pathways revealed that the process of piperazine ring cleavage and decarboxylation also generates H protons, further promoting the production of H2. Therefore, the effective spatial separation and transfer of the photoinduced carriers are attributed to the good band structure, large specific surface area, and cooperative reduction and oxidation reactions of UiO-66@Zn0.5Cd0.5S, resulting in significant photocatalytic activity. The toxicity assessment of antibiotics and intermediate products during the photocatalytic reaction also verifies the reduction of environmental risk. This study highlights a promising way to expand the application of the MOFs-based photocatalyst in clean energy conversion coupling with water remediation.

Efficient Cr(VI) remediation by electrospun composite porous nanofibers incorporating biomass with metal oxides and metal-organic framework

To develop a highly efficient adsorbent to remediate and remove hexavalent chromium ions (Cr(VI)) from polluted water, cellulose acetate (CA) and chitosan (CS), along with metal oxides (titanium dioxide (TiO2) and ferroferric oxide (Fe3O4)), and a zirconium-based metal-organic framework (UiO-66) were used to fabricate the composite porous nanofiber membranes through electrospinning. The adsorption performance, influencing factors, adsorption kinetics and isotherms of composite nanofiber membranes were comprehensively investigated. The multi-layer membrane with interpenetrating nanofibers and surface functional groups enhanced the natural physical adsorption and provided potential chemical sites. The thermal stability was improved by introducing TiO2 and UiO-66. CA/CS/UiO-66 exhibited the highest adsorption capacity (118.81 mg g-1) and removal rate (60.76%), which were twice higher than those of the control. The correlation coefficients (R2) of all the composite nanofibers regressed by the Langmuir model were significantly higher than those by the Freundlich model. The pseudo-first-order kinetic curve of CA/CS composite nanofibers showed the highest R2 (0.973), demonstrating that the whole adsorption process involved a combination of strong physical adsorption and weak chemical adsorption by the amino groups of CS. However, the R2 values of the pseudo-second-order kinetic model increased after incorporating TiO2, Fe3O4, and UiO-66 into the CA/CS composite nanofiber membranes since an enhanced chemical reaction with Cr (VI) occured during the adsorption.

Twinned crystal Cd0.9Zn0.1S/MoO3 nanorod S-scheme heterojunctions as promising photocatalysts for efficient hydrogen evolution

Leveraging solar energy through photocatalytic hydrogen production from water stands out as one of the most promising approaches to address the energy and environmental challenges. The choice of catalyst profoundly influences the outcomes of photocatalytic reactions, and constructing heterojunctions has emerged as a widely applied strategy to overcome the limitations associated with single-phase photocatalysts. MoO3, renowned for its high chemical stability, encounters issues such as low photocatalytic efficiency and fast recombination of photogenerated electrons and holes. To tackle these challenges, the morphology of MoO3 has been controlled to form nanorods, simultaneously suppressing the aggregation of the catalyst and increasing the number of surface-active sites. Moreover, to facilitate the separation of photogenerated charge carriers, Cd0.9Zn0.1S nanoparticles with a twin crystal structure are deposited on the surface of MoO3, establishing an S-scheme heterojunction. Experimental findings demonstrate that the synergistic effects arising from the well-defined morphology and interface interactions extend the absorption range to visible light response, improve charge transfer activity, and prolong the lifetime of charge carriers. Consequently, Cd0.9Zn0.1S/MoO3 S-scheme heterojunctions exhibit outstanding photocatalytic hydrogen production performance (3909.79 μmol g-1 h-1) under visible light irradiation, surpassing that of MoO3 by nearly nine fold.

Metal-Organic Frameworks-Derived Nanocarbon Materials and Nanometal Oxides for Photocatalytic Applications

Harnessing low-density solar energy and converting it into high-density chemical energy through photocatalysis has emerged as a promising avenue for the production of chemicals and remediation of environmental pollution, which contributes to alleviating the overreliance on fossil fuels. In recent years, metal-organic frameworks (MOFs) have gained widespread application in the field of photocatalysis due to their photostability, tunable structures, and responsiveness in the visible light range. However, most MOFs exhibit relatively low response to light, limiting their practical applications. MOFs-derived nanomaterials not only retain the inherent advantages of pristine MOFs but also show enhanced light adsorption and responsiveness. This review categorizes and summarizes MOFs-derived nanomaterials, including nanocarbons and nanometal oxides, providing representative examples for the synthetic strategies of each category. Subsequently, the recent research progress on MOFs-derived materials in photocatalytic applications are systematically introduced, specifically in the areas of photocatalytic water splitting to H2, photocatalytic CO2 reduction, and photocatalytic water treatment. The corresponding mechanisms involved in each photocatalytic reaction are elaborated in detail. Finally, the review discusses the challenges and further directions faced by MOFs-derived nanomaterials in the field of photocatalysis, highlighting their potential role in advancing sustainable energy production and environmental remediation.

Construction of SU-102 for adsorption and photocatalytic synergistic removal of tetracycline

Tetracycline (TC) is a significant group of broad-spectrum antibiotics that are frequently employed in medical health and animal husbandry. However, the problem of TC residues has been increasing globally with the large-scale production and widespread use, posing a serious threat to the human health and ecological environment. In this paper, a green plant-based MOF SU-102 was prepared, and the adsorption characteristics of SU-102 on TC were investigated. SU-102 was columnar crystal with considerable specific surface area and pore structure, and it could adsorb TC quickly and effectively. And compared to SU-102-a, the adsorption rate of TC by SU-102-b has increased by nearly four times. The adsorption reaction was a spontaneous, entropy-gaining, heat-absorbing process. The adsorption mechanisms between SU-102 and TC were π-π interaction and hydrogen bonding. In addition, SU-102 also had considerable photocatalytic properties, and its application in adsorbent desorption treatment effectively solved the problem of secondary pollution.

An Updated Overview of Magnetic Composites for Water Decontamination

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

A Visible Light-Driven α-MnO2/UiO-66-NH2 S-Scheme Photocatalyst toward Ameliorated Oxy-TCH Degradation and H2 Evolution

Photocatalytic hydrogen production and pollutant degradation using a heterogeneous photocatalyst remains an alternative route for mitigating the impending pollution and energy crisis. Hence, the development of cost-effective and environmentally friendly semiconducting materials with high solar light captivation nature is imperative. To overcome this challenge, α-MnO2 nanorod (NR)-modified MOF UiO-66-NH2 (UNH) was prepared via a facile solvothermal method, which is efficient toward H2 evolution and oxy-tetracycline hydrochloride (O-TCH) degradation. The field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM) results of the α-MnO2@UNH (MnU) hybrid reveals its nanorod embedded in MOF matrix, and the X-ray photoelectron spectroscopy (XPS) result confirms the interaction of UNH moiety with α-MnO2 NRs. Additionally, the outstanding separation of photogenerated excitons and the charge-transfer efficacy are further validated by photoluminescence (PL), time-resolved photoluminescence (TRPL), electrochemical impedance spectroscopy (EIS), and transient photocurrent analysis, which are the key causes for photoactivity augmentation in the MnU composites. The MnU-2 composite shows a superior O-TCH degradation efficiency of 93.23% and an excellent H2 production rate of about 410.6 μmol h-1 upon light irradiation. This study provides significant evidence in favor of the suggested mediator-free S-scheme-adapted charge migration path, and it effectively explains the enhanced exciton separation leading to extraordinary catalytic efficiency of the proposed composite.

Electron-deficient Fe3O4@AC-NH2@Cu-MOF nanoparticles for enhanced degradation of electron-rich benzene derivatives via synergistic adsorption and catalytic oxidation

Benzene derivatives in wastewater have negative impacts on ecosystems and human health, making their removal prior to discharge imperative. In this study, Fe3O4@AC-NH2@Cu-opa (AC-NH2 = aminoclay, Cu-opa = [Cu(opa)(bipy)0.5(H2O)]n (H2opa = 3-(4-oxypyridinium-1-yl) phthalic acid)) nanoparticles (NPs) were synthesized as adsorbent and catalyst for phenolic compound removal from wastewater. Fe3O4@AC-NH2@Cu-opa NPs demonstrated outstanding performance in the adsorption of phenol, exhibiting a remarkable adsorption capacity of up to 166.39 mg g-1 according to the Langmuir model. The composite also exhibited higher Fenton activity toward the degradation of electron-rich organic phenolic pollutants, with a rate approximately 3.4 times higher than that of Fe3O4 alone. The high catalytic activity of the composite was attributed to the large surface area and abundant active sites of the 2D charge-separated Cu-MOF. Meanwhile, the superparamagnetism of the Fe3O4 core enabled magnetic recollection and reuse without any significant loss of activity. Therefore, use of Fe3O4@AC-NH2@Cu-opa/H2O2 shows potential in an efficient method for the removal of phenolic compounds from wastewater.

Augmented photocatalysis induced by 1T-MoS2 bridged 2D/2D MgIn2S4@1T/2H-MoS2 Z-scheme heterojunction: mechanistic insights into H2O2 and H2 evolution

In the realm of composite photocatalysts, the fusion of the co-catalyst effect with interfacial engineering is recognized as a potent strategy for facilitating the segregation and migration of photo-induced charge carriers. Herein, an innovative mediator-based Z-scheme hybrid, i.e. MIS@1T/2H-MoS2, has been well designed by pairing MIS with 1T/2H-MoS2via a facile hydrothermal strategy as a competent photocatalyst for H2O2 and H2 generation. The co-catalyst, i.e. metallic 1T-phase bridging between semiconducting 2H-MoS2 and MIS, serves as a solid state electron mediator in the heterostructure. Morphological findings revealed the growth of 1T/2H-MoS2 nanoflowers over MIS microflowers, verifying the close interaction between MIS and 1T/2H-MoS2. By virtue of accelerated e-/h+ pair separation and migration efficiency along with a proliferated density of active sites, the MMoS2-30 photocatalyst yields an optimum H2O2 of 35 μmol h-1 and H2 of 370 μmol h-1 (ACE of 5.9%), which is 3 and 2.7 fold higher than pristine MIS. This obvious enhancement can be attributed to photoluminescence and electrochemical aspects that substantiate the diminished charge transfer resistance along with improved charge carrier separation, representing a good example of a noble metal-free photocatalyst. The proposed Z-scheme charge transfer mechanism is aided by time-resolved photoluminescence (TRPL), XPS, radical trapping experiments, and EPR analysis. Overall, this endeavour provides advanced insights into the architecture of noble metal-free Z-scheme heterostructures, offering promising prospects in photocatalytic applications.

Synthesis of cellulose cotton-based UiO-66 MOFs for the removal of rhodamine B and Pb(II) metal ions from contaminated wastewater

The presence of pollutants in drinking water has become a significant concern recently. Various substances, including activated carbon, membranes, biochar, etc., are used to remove these pollutants. In the present study, a new composite comprising cotton fabric and a mixture of Metal-Organic Frameworks (MOFs) was synthesized and used as an adsorbent for eliminating pollutants from wastewater. At first, the UiO-66 MOFs were prepared by a simple method of reacting Zirconium (IV) chloride (ZrCl4) and p-Phthalic acid (PTA) after successful preparation of UiO-66 then modified its surface with amino functional groups by reacting with APTES to obtain UiO-66-NH2. Moreover, the cellulose cotton fabric (CF) surface was modified with Polydopamine (PDA) and obtained CF@PDA. Further, with the help of EDC-HCl and NHS, the UiO-66-NH2 grafted on the surface of the CF@PDA and finally obtained CF@PDA/UiO-66-NH2. In addition, the adsorption study was performed toward RhB dye and Pb(II) metal ion pollutants. The maximum adsorption toward RhB dye was 68.5 mg/g, while toward Pb(II) metal ions was 65 mg/g. In addition, the kinetic study was also conducted and the result favoured the Pseudo-second order kinetic study. The adsorption isotherm was also studied and the Langmuir model was more fitted as compared with the Freundlich model. Moreover, the material has excellent regeneration and recycling ability after ten cycles. The significant adsorption ability, the novel combination of cotton and MOFs, and the recycling feature make our material CF@PDA/UiO-66-NH2 a promising potential absorbent material for wastewater treatment and even in other important areas of water research.

Study on adsorption of salicylic acid and sulfosalicylic acid by MOF-sodium alginate gel beads obtained in a green way

A composite (ZS-UiO-66-NH2) zirconium crosslinked sodium alginate gel beads (ZS)-metal-organic skeleton (UiO-66-NH2) were prepared in this study through in-situ growth under simple, green and mild conditions for removal of the salicylic acid (SA) and sulfosalicylic acid (SSA) from water. The physicochemical properties of ZS-UiO-66-NH2 were characterized using various analytical methods. The influencing factors in the adsorption process including pH of solution, amount of adsorbent, coexisting ions, adsorption time, reaction temperature and equilibrium concentration of SA/SSA were performed in batch adsorption. The experimental results indicated that ZS-UiO-66-NH2 had high stability and could achieve efficient adsorption of SA/SSA in broad pH range (2-9) and salinity (0-0.2 mol·L-1). SA and SSA adsorbed on the composite at 293 K reached high values of 193 and 167 mg·g-1 from Langmuir model, respectively. Kinetic and isotherm studies demonstrated that the adsorption processes were mainly multilayer heterogeneous chemisorption. Thermodynamic data manifested that the two processes were exothermic and spontaneous with increasing entropy. ZS-UiO-66-NH2 can effectively remove SA/SSA from simulated wastewater under different pH and can be reused after elution with a NaHCO3 solution (5 mmol·L-1). The ZS-UiO-66-NH2 composite has great potential for removing SA/SSA from actual water bodies.

UiO-66 octahedrons for adsorptive removal of direct blue-6: process optimization, interaction mechanism, and phytotoxicity assessment

The materials for water treatment have been evolving in multitude of dimensions, indicating the importance of water reuse and increasing level of water pollution around the globe. Among the various materials that are utilized in wastewater treatment, the material that has attracted the research community for the past decades is the metal organic framework (MOF). In this work one of the water stable and microporous MOF, UiO-66, and its aminated version has been employed to adsorb an anionic azo dye, direct blue-6 (DB-6), from the aqueous matrix. Performance of both the MOFs was compared to know the efficiency under varying solution conditions. The optimized parameters for DB-6 adsorption by UiO-66 was performed using response surface methodology. This numerical optimization was further extended with canonical and ridge analysis. Under optimal conditions, the materials were exhibiting a good adsorption capacity of 754.4 mg/g. The materials were analyzed in terms of morphology, crystallinity, thermal stability, and surface area using instruments like X-ray diffraction, electron microscopy, thermogravimetric analysis, and BET surface area analysis. The mechanism of interaction between UiO-66 and DB-6 molecule was elucidated with the help of XPS analysis which helps to know the main interacting group of UiO-66. This study was concluded with a phytotoxicity analysis of DB-6 and the antioxidant system of Vigna radiata assessed using pre and post adsorbed water.

MgIn2S4/UiO-66-NH2 MOF-Based Heterostructure: Visible-Light-Responsive Z-Scheme-Mediated Synergistically Enhanced Photocatalytic Performance toward Hydrogen and Oxygen Evolution

Hydrogen and oxygen evolution via photocatalytic water splitting remains the quintessential alternative to fossil fuels. Photocatalysts must be sufficiently robust, competent, and productive toward harnessing sunlight in order to utilize the solar spectrum for maximal photocatalytic output. Herein, we have fabricated the MgIn₂S₄/UiO-66-NH₂ composite via a facile solvothermal route and have determined its efficacy toward light-induced H₂ and O₂ generation reactions through water splitting with the aid of different sacrificial agents. Initially, the formation of pristine and composite materials was ascertained by PXRD, FTIR, etc. Moreover, with the aid of sophisticated morphological characterization techniques (FESEM and HRTEM), the intricate interaction between MgIn₂S₄ and UiO-66-NH₂ was revealed. Additionally, the XPS studies suggested the effective interaction between the individual components with binding energy shifting suggesting the transfer of electrons from Zr-MOF to MgIn₂S₄. The PL and electrochemical aspects supported the effective photogenerated charge segregation in the prepared composite leading to superior photocatalytic outputs. Amidst the prepared composites of (3, 5, and 7 wt %) MgIn₂S₄/UiO-66-NH₂, the 5 wt % or UM-2 composite displays optimal H₂ and O₂ evolution performances of 493.8 and 258.6 μmol h^-1 (4-fold greater than for pristine MgIn₂S₄ and UiO-66-NH₂), respectively. The nanocomposite's enhanced performance is indeed a consequence of the coadjuvant interaction among pristine UiO-66-NH₂ and MgIn₂S₄ components that transpires via the Z-scheme-mediated charge transfer by enabling facile exciton segregation and channelization. Moreover, the composite inherited the remarkable framework stability of parent Zr-MOF, and the MgIn₂S₄ insertion had a negligible impact on the framework integrity. This work will offer a valuable model for developing robust Zr-MOF-based nanocomposite photocatalysts and evaluating their superior performance toward photocatalytic water redox reactions.

Effective adsorptive removal of sulfamethoxazole (SMX) from aqueous solution by ZIF-8 derived adsorbent ZC-0.5

Efficient removal of antibiotics from the aquatic environment is urgently needed due to their obstinate accumulation and non-biodegradability. In this study, a mesoporous carbon material (ZC-0.5) was successfully synthesized for the adsorption of sulfamethoxazole (SMX), one of the major antibiotics for the treatment of human and animal infections. ZIF-8 as the precursor of ZC-0.5, specifically, using cetyl trimethyl ammonium bromide (CTAB) and sodium laurate (SL) as dual templates and carbonizing at 800 ℃. This novel adsorbent exhibited a high proportion of mesopore (75.64%) and a large specific surface area (1459.73 m²·g^-1). The adsorption experiment examined the reusability of ZC-0.5 and that it could retain superior maximum adsorption capacities (167.45 mg∙L^-1) after five cycles of adsorption and desorption. The adsorption process satisfied the pseudo-second-order kinetic (PSO) and mixed first- and second-order kinetic (MOE). It also satisfied the Freundlich and Sips isotherm models. Moreover, thermodynamic calculation indicated the adsorption process was spontaneous, endothermal, and entropy-increasing. Furthermore, plausible adsorption mechanisms were explained through van der Waals force, electrostatic interaction, hydrophobic force, π-π interaction, and hydrogen bond. This work offers a new efficient adsorbent for antibiotic elimination.

Highly efficient removal of Se(IV) using reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO): selenium removal mechanism

Se(IV) removal using nanoscale zero-valent iron (nZVI) has been extensively studied. Still, the synergistic removal of Se(IV) by reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) has not been reported. In this study, nZVI/rGO was successfully synthesized for Se(IV) removal from wastewater. The effects of different environmental conditions (load ratio, dosage, initial pH) on Se(IV) removal by nZVI/rGO were investigated. When the load ratio is 10%, the dosage is 0.3 g/L, the initial pH is 3, and the removal rate is 99%. The adsorption isotherm and kinetics accorded with the Langmuir isotherm and first-order kinetics models (R² > 0.99). The fitted maximum adsorption capacity reached up to 173.53 mg/g. NZVI/rGo and Se(IV) is a spontaneous endothermic reaction (△G < 0, △H > 0) and is characterized by EDS, XRD, and XPS before and after the reaction, to further clarify the reaction mechanism. The XPS narrow spectrum analysis suggested that Se(IV) was reduced to elemental selenium (Se(0)), while the intermediate Fe(II) was oxidized to form hydroxide precipitation. Therefore, nZVI/rGO was favored for Se-contaminated wastewater remediation.

Introducing anthracene and amino groups into Ln-OFs for the photoreduction of Cr(vi) without additional photosensitizers or cocatalysts

The stable LCUH-100 was designed and synthesized, by incorporating chromophores into lanthanide MOFs, as a high-efficiency photocatalyst, which can rapidly and efficiently reduce Cr(vi) under visible-light irradiation and has good cycle stability.

Hydrolytically stable mixed ditopic linker based zirconium metal organic framework as a robust photocatalyst towards Tetracycline Hydrochloride degradation and hydrogen evolution

In the existing eco-crisis, designing and engineering an efficient as well as water stable photocatalyst for energy conversion and pollutant abatement remains crucial. In this regard, a mixed linker type zirconium metal organic framework (Zr-MOF) with terepthalic acid based ditopic linkers were utilized to design a single component photocatalyst through single step solvothermal method to utilize photons from visible light illumination towards hydrogen energy (H2) production and Tetracycline Hydrochloride (TCH) degradation. The one pot synthesized mixed linker based Zr-MOF displays visible light absorption through band gap tuning, superior exciton segregation and oxygen vacancy that cumulatively supports the enhancement in the photocatalytic output with respect to their pristine counterparts. Additionally, the X-ray photoelectron spectroscopy, optical and electrochemical studies strongly reinforces the above claims. The prepared mixed linker Zr-MOF showed superior photocatalytic H2 evolution performance of 247.88 µmol h-1 (apparent conversion efficiency; ACE = 1.9%) that is twice than its pristine Zr-MOFs. Moreover, in TCH degradation, the mixed linker MOF displays an enhanced efficacy of 91.8 % and adopts pseudo-first order type kinetics with a rate constant value of 0.032. Typically, the active species participating for the TCH photo-degradation follows the order of hydroxyl (OH.) < superoxide (O2.-) radicals. Consequently, the mixed linker Zr-MOF could be effectively used as a robust photocatalyst exhibiting boosted TCH degradation and H2 production.

Hierarchical S-Scheme Heterostructure of CdIn2S4@UiO-66-NH2 toward Synchronously Boosting Photocatalytic Removal of Cr(VI) and Tetracycline

Developing highly efficient photocatalysts toward synchronously removing heavy metals and organic pollutants is still a serious challenge. Herein, we depict hierarchical S-scheme heterostructured photocatalysts prepared via in situ anchoring UiO-66-NH₂ nanoparticles onto the CdIn₂S₄ porous microsphere structures assembled with numerous nanosheets. In the mixed system of Cr(VI) and tetracycline (TC), the optimal photocatalyst (CIS@U66N-30) shows remarkable photocatalytic activities toward the synchronous removal of Cr(VI) (97.26%) and TC (close to 100% of) under visible-light irradiation for 60 min, being the best removal rates among those of the reported photocatalysts, and sustains the outstanding stability and reusability. Its reaction rate constants of Cr(VI) reduction and TC degradation are about 2.06 and 1.58 folds that in the single Cr(VI) and TC systems, respectively. The enhanced photocatalytic activities of CIS@U66N-30 mainly result from the following synergism: (1) its hierarchical structure offers abundant active sites, and the S-scheme migration mechanism of charge carriers in the heterostructure accelerates the separation and migration of the useful photoinduced electrons and holes with the high redox capability; (2) Cr(VI) and TC can serve as the electron scavenger for TC oxidation degradation and the hole and ^•OH scavenger for Cr(VI) reduction, respectively, further enhancing the separation and utilization efficiency of photoinduced electrons and holes. Besides, the possible TC degradation pathway and plausible S-scheme photocatalytic mechanism over CIS@U66N-30 for the concurrent elimination of Cr(VI) and TC are proposed.

Efficient Removal of Inorganic and Organic Pollutants over a NiCo2O4@MOF-801@MIL88A Photocatalyst: The Significance of Ternary Heterojunction Engineering

Energy problems are a substantial concern in a global society that can be solved by replacing with sustainable energies. In recent years, designing nanomaterials as photocatalysts that can produce chemical energy with the utilization of infinite visible light energy became a new solution for water treatment. In the present study, NiCo₂O₄@MOF-801 has been synthesized with multiple properties, and then, a novel three-layer NiCo₂O₄@MOF-801@MIL88A photocatalyst has been successfully synthesized to improve meropenem degradation and Cr(VI) reduction. The prepared photocatalyst was characterized by XRD, IR, XPS, TEM, SEM, TGA, BET, EIS, PL, and UV-vis. According to the structural and optical analysis performed, the interaction between the components formed a heterojunction structure that prevented the recombination of charge carriers and increased the photocatalytic performance. Photocatalytic simulation tests also proved the reduction of chromium and degradation of antibiotics to find the optimal heterogeneous performance. As a result, the NiCo₂O₄@MOF-801@MIL88A composite can completely reduce Cr(VI) in 45 min, which is strongly preferable to any pure component's performance. Overall, this work offers a low-cost but high-efficiency material that can remove organic and inorganic contaminants from water.

Multi-Functionalization Integration into the Electrospun Nanofibers Exhibiting Effective Iodine Capture from Water

Efficient capture of radioiodine from aqueous solutions is of importance for sustainable development of nuclear energy and protection of the environment. However, current adsorbents under exploration suffer from limited adsorption capacity and powder form that are unfavorable for practical applications. Herein, we applied a "multi-functionalization integration" idea to construct novel electrospun fiber adsorbents (N-MOF-PAN fibers) containing cationic quaternary ammonium groups, uncharged amine groups, and porous MOF material (UiO-66-NH₂), which in synergy adsorb iodine effectively from both saturated I₂ aqueous solution and I₃^- aqueous solution. Iodine species (94.6%) could be removed from saturated I₂ solution within 180 min, and 98.7% of iodine species were captured from I₃^- solution within 240 min. Additionally, the N-MOF-PAN fibers exhibited high iodine uptake capacities of 3.56 g g^-1 from a concentrated KI/I₂ aqueous solution and 3.61 g g^-1 from the Langmuir isotherm model, surpassing many reported iodine adsorbents in the aqueous medium. Characterization and mechanism analysis indicated that multiple active sites simultaneously attribute to the high binding affinity toward iodine species through physical adsorption and chemical adsorption. Furthermore, benefiting from their macroscopic architecture, N-MOF-PAN fibers were used as the adsorption column for dynamic iodine capture with a bed volume of 1490 mL, which is much higher than commercially activated carbons. Overall, this work provides guidance for the development of novel fiber adsorbents for related applications.

Recent Progress of Metal-Organic Frameworks and Metal-Organic Frameworks-Based Heterostructures as Photocatalysts

In the field of photocatalysis, metal-organic frameworks (MOFs) have drawn a lot of attention. MOFs have a number of advantages over conventional semiconductors, including high specific surface area, large number of active sites, and an easily tunable porous structure. In this perspective review, different synthesis methods used to prepare MOFs and MOFs-based heterostructures have been discussed. Apart from this, the application of MOFs and MOFs-based heterostructures as photocatalysts for photocatalytic degradation of different types of pollutants have been compiled. This paper also highlights the different strategies that have been developed to modify and regulate pristine MOFs for improved photocatalytic performance. The MOFs modifications may result in better visible light absorption, effective photo-generated charge carriers (e-/h+), separation and transfer as well as improved recyclability. Despite that, there are still many obstacles and challenges that need to be addressed. In order to meet the requirements of using MOFs and MOFs-based heterostructures in photocatalysis for low-cost practical applications, future development and prospects have also been discussed.

Synthesis of ferroferric oxide@silicon dioxide/cobalt-based zeolitic imidazole frameworks for the removal of doxorubicin hydrochloride from wastewater

Due to its low-cost, eco-friendliness and easy mode of separation biosynthesized magnetic ferroferric oxide (Fe₃O₄) can be successfully used for the removal of organic contaminants from wastewater. However, there are some challenges that to date have limited this compound's practical removal efficiency. Thus, in this study, a cobalt-based zeolitic imidazole frameworks (ZIF-67) coated biosynthesized ferroferric oxide@silicon dioxide (Fe₃O₄@SiO₂) magnetic composite (Fe₃O₄@SiO₂/ZIF-67) was prepared to address these issues and subsequently used to remove doxorubicin hydrochloride (DOX). Characterization results showed that the fabricated composite exhibited significant magnetic properties (16.1 emu·g^-1) with a size ranging between 50 and 250 nm. The amount of DOX adsorbed by the composite (90.7 mg·g^-1) was much higher than either of the component parts, which were only 35.7 and 82.5 mg·g^-1 for Fe₃O₄@SiO₂ and ZIF-67 respectively. This indicated enhanced DOX adsorption by Fe₃O₄@SiO₂/ZIF-67. The DOX adsorption best fit a pseudo-second order kinetic and Langmuir adsorption model. These studies suggested that the DOX adsorption mechanism involved a combination of electrostatic interactions, π-π stacking, hydrogen bonding and pore filling. Regeneration and application studies, exposing Fe₃O₄@SiO₂/ZIF-67 to real water samples, practically demonstrated that Fe₃O₄@SiO₂/ZIF-67 with propensity for magnetic separation and recycle is a promising nanomaterial for DOX removal.

Preparation of Highly Stable DUT-52 Materials and Adsorption of Dichromate Ions in Aqueous Solution

Highly stable DUT-52 materials were synthesized by the hydrothermal method and well-characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). In order to systematically study the adsorption of dichromate ions in aqueous solution by the DUT-52 materials, a single factor experiment, kinetic experiment, thermodynamic experiment, competition ion experiment, and material regeneration experiment were designed. Based on the H-bond interaction between the dichromate ions and the H atoms of a NDC^2- ligand, the DUT-52 materials showed a maximum removal rate of 96.4% and a maximum adsorption capacity of 120.68 mg·g^-1 with excellent selective adsorption and material regeneration. In addition, the process of adsorption of dichromate ions by the DUT-52 materials is in accordance with the pseudo second-order kinetics and Langmuir models, and the adsorption mechanism and the important role of the H-bond interaction were reasonably explained using the XPS pattern and theoretical calculation. Accordingly, DUT-52 can be regarded as a multifunctional material for efficiently removing dichromate ions from the wastewater.

Metal organic framework-based Janus nanomaterials: rational design, strategic fabrication and emerging applications

Janus nanoparticles (JNPs) with dual segments comprising chemically distinct compositions have garnered the attention of researchers in the past few years. The combination of different materials with diversified morphology, topology, and distinct physico-chemical characteristics into the single Janus nanocrystal has yielded multifarious capabilities for a myriad of emerging applications involving catalysis, gas separation, electro-catalysis, adsorption and energy storage. However, the traditional Janus entities significantly lack the need for populous active sites and high surface area. To overcome the textural hurdles and improve the functionalities of JNPs, porous MOFs were eventually introduced into Janus particles. MOFs are well endowed with varied pore apertures, structures, large surface areas and tailored characteristics, making them potentially invaluable for Janus fabrication. Depending upon the usage, MOFs can be explored to design Metal@MOF, polymetalic@MOF, MOF@MOF and MOF-derived JNPs. In this regard, we have represented a holistic summarization of the design, synthesis and emerging applications of a rising class of multi-functionalized MOF-based Janus nanomaterials. Moreover, this article will significantly aid researchers with a vision of creating dual-composition porous nanomaterials as the MOF-based Janus nanoparticles is at infancy.

Mixed-Valence Bimetallic Ce/Zr MOF-Based Nanoarchitecture: A Visible-Light-Active Photocatalyst for Ciprofloxacin Degradation and Hydrogen Evolution

A mixed-valency bimetallic Ce/Zr MOF with Ce³⁺/Ce⁴⁺ ions incorporated and an oxygen vacancy-rich single-component photocatalyst have been designed through the one-step solvothermal route to harness photons from the visible-light spectrum for green energy (H₂) generation and ciprofloxacin (CIP) degradation. The one-pot-engineered bimetallic Ce/Zr MOF shows visible-light-active characteristics accompanied by a narrower band gap, along with enhanced exciton separation and superior ligand-to-metal charge transfer (LMCT), due to the presence of an interconvertible Ce³⁺/Ce⁴⁺ ions pair in comparison to its pristine MOF counterpart. The Ce ion insertion led to increase in electron density around the Zr⁴⁺ ion, along with generation of some oxygen vacancies (OV), which cumulatively led to the rise in the photo-reaction output. The synthesized UNH (Ce/Zr 1:1) MOF displayed a boosted photocatalytic H₂ production rate of 468.30 μmol h^-1 (ACE = 3.51%), which is around fourfolds higher than that of pristine MOFs. Moreover, for CIP photodegradation, the UNH (Ce/Zr 1:1) shows an enhanced efficiency of 90.8% and follows pseudo-first-order kinetics with a rate constant of 0.0363. Typically, the active species involved in the photo-redox reaction of the CIP photodegradation follows the order hydroxyl radical (OH^•) < superoxide radical (O₂^•-), as confirmed by the TA and NBT tests. Consequently, the bimetallic Ce/Zr MOF can be readily employed as a robust photocatalyst with enhanced tendencies towards CIP degradation and H₂ evolution.

Facile One-Pot Synthesis of Zn/Mg-MOF-74 with Unsaturated Coordination Metal Centers for Efficient CO2 Adsorption and Conversion to Cyclic Carbonates

Bimetallic metal-organic frameworks (MOFs) containing two different inorganic metal nodes exhibited enhanced properties in CO₂ adsorption and catalytic conversion compared with the corresponding monometallic MOFs. In this work, the novel bimetallic Zn/Mg-MOF-74 with different ratios of Zn/Mg was synthesized successfully by a facile one-pot method. Powder X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy/transmission electron microscopy, N₂/CO₂ adsorption/desorption, and CO₂/NH₃-temperature-programmed desorption techniques thoroughly characterized the structure, morphology, and physicochemical properties of Zn/Mg-MOF-74. Besides the excellent CO₂ adsorption capacity (128.3 cm³/g at 273 K and 1 bar), Zn_0.75Mg_0.25-MOF-74 also showed efficient catalytic activity for the cycloaddition reaction of CO₂ and epoxides to cyclic carbonates with outstanding yield and selectivity all over 99% under solvent-free and mild conditions (60 °C, 0.8 MPa), outperforming the mechanical combination of Zn-MOF-74 and Mg-MOF-74 with the same metal contents, indicating the synergistic effect of two adjacent metals in bimetallic MOF-74. In addition, the Zn_0.75Mg_0.25-MOF-74 catalyst could be recycled for at least five runs and possess good versatility to various substrates. Finally, a feasible mechanism of the catalytic reaction was proposed. Thanks to the high surface area, affinity toward CO₂, and accessibility of multiple active sites of the unsaturated metal centers as active Lewis acid sites and O atoms from Zn-O and Mg-O as Lewis basic sites, efficient chemical fixation of CO₂ to cyclic carbonates was obtained over the Zn_0.75Mg_0.25-MOF-74 catalyst. The present facile synthesis and application of a robust bimetallic MOF catalyst offered a competitive avenue for the integration of CO₂ adsorption and CO₂ catalytic conversion.