A type-II interband alignment heterojunction architecture of cobalt titanate integrated UiO-66-NH2: A visible light mediated photocatalytic approach directed towards Norfloxacin degradation and green energy (Hydrogen) evolution

Ferrocenyl Lawesson's reagent-based porous organic polymers for efficient adsorption-assisted photocatalysis degradation of organic dyes

The adsorption process followed by photodegradation, adsorption-assisted photocatalysis, is an efficient way to achieve an enhanced overall removal of pollutants from wastewater. This aim can be achieved by a new type of metallocene-based porous organic polymers, denoted as Ferrocenyl Lawesson's reagent-metal-organic porous polymers (FcLR-MOPPs), including FcLR-P1 and FcLR-P2, synthesized through 1) synthesis of ferrocene-MOPPs (ferrocene-P1 and ferrocene-P2) through a Friedel-Crafts reaction between dimethoxymethane and ferrocene at two different ratios of 3:1 and 5:1 and 2) reaction of the ferrocene-MOPPs with phosphonium pentasulfide (P2S5). The photodegradation efficiencies of methylene blue (MB) and methyl orange (MO) toward FcLR-MOPPs were higher than those of the ferrocene-MOPPs. In contrast, the adsorption efficiencies of the dyes declined after the reaction of ferrocene-MOPPs with P2S5. In both cases, a higher photocatalytic activity and adsorption affinity were observed towards MB dye. When combined degradation/adsorption of dyes was investigated, a boosted dye elimination was observed for both the MOPP-based catalysts. FcLR-P1, as the optimal catalyst with the MB degradation/adsorption efficiency of 87.0 % ± 3.0, indicated a pseudo-first-order kinetic model for degradation of MB with a degradation rate constant of 0.074 min-1, a pseudo-second-order kinetic model and Langmuir isotherm for adsorption of MB, and high reusing after three cycles of use. A band gap energy (Eg) value of +2.3 eV was determined for FcLR-P1 via Tauc plots, consistent with the Eg value obtained from the cyclic voltammetry curves (+1.98 eV). Mott-Schottky plots consistent with radical trapping experiments indicated •OH species as the critical species in the MB photodegradation.

Inexpensive Carbon Based Co-Catalyst Modified Zr-MOF Towards Photocatalytic H2O2 and H2 Production

The photocatalytic H2O2 and H2 production are the utmost encouraging paths to overcome the imminent energy crisis. For accomplishing these goals the photocatalysts needs to be stable, trap photons and superior exciton separation, yet these properties are scanty for aqueous stable UiO-66-NH2. Hence, UiO-66-NH2 is armed with inexpensive Carbon nanoparticles that were incorporated through facile solvothermal procedure are employed towards photocatalytic H2 and H2O2 production. The UC-2 composite exhibits improved photocatalytic activity, which was ascribed to the composites capacity to suppress exciton re-combination, enhanced photon capture and to facilitate quicker charge transfer that was observed from UV-Vis DRS, EIS, PL, TRPL and transient photocurrent analysis. Composite UC-2 exhibits an H2O2 generation rate of 33.2 μmol h-1 in an O2 saturated conditions with isopropyl alcohol and water underneath visible light irradiation. This H2O2 generation rate was nearly three folds higher than the pristine UiO-66-NH2 MOF. Moreover, the produced materials were subjected to a photocatalytic H2 evolution research, and similar results were obtained, indicating that UC-2 has the maximum H2 evolution capacity at 298.1 μmol h-1. Typically, the light trapping tendency, remarkable electron transfer capacity and electron capture capacity of the carbon NPs based co-catalyst aids to improve the overall photo-reaction performance thereby producing superior photocatalytic H2O2 and H2 as a sustainable energy alternative.

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.

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.

Machine-Learning-Assisted Aggregation-Induced Emissive Nanosilicon-Based Sensor Array for Point-of-Care Identification of Multiple Foodborne Pathogens

How timely identification and determination of pathogen species in pathogen-contaminated foods are responsible for rapid and accurate treatments for food safety accidents. Herein, we synthesize four aggregation-induced emissive nanosilicons with different surface potentials and hydrophobicities by encapsulating four tetraphenylethylene derivatives differing in functional groups. The prepared nanosilicons are utilized as receptors to develop a nanosensor array according to their distinctive interactions with pathogens for the rapid and simultaneous discrimination of pathogens. By coupling with machine-learning algorithms, the proposed nanosensor array achieves high performance in identifying eight pathogens within 1 h with high overall accuracy (93.75-100%). Meanwhile, Cronobacter sakazakii and Listeria monocytogenes are taken as model bacteria for the quantitative evaluation of the developed nanosensor array, which can successfully distinguish the concentration of C. sakazakii and L. monocytogenes at more than 103 and 102 CFU mL-1, respectively, and their mixed samples at 105 CFU mL-1 through the artificial neural network. Moreover, eight pathogens at 1 × 104 CFU mL-1 in milk can be successfully identified by the developed nanosensor array, indicating its feasibility in monitoring food hazards.

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.

Ag2O@UiO-66 new thin film as p-n heterojunction: permanent photoreduction of hexavalent Cr

The new nanosphere Ag2O@UiO-66 thin-film was synthesized on a stainless steel mesh surface via an electrophoretic deposition method, and is used as an effective and low-cost photocatalyst using visible light. The synthesized nanocomposite was used to perform photo-reduction of Cr(vi) ions under white light irradiation. The best removal rate (72% after 15 minutes) was obtained by the film with 0.034 grams of deposited composite having relative percentages of Ag2O : UiO-66 of 70 : 30. The interesting obtained results confirm that the p-n heterojunction of the composite is the main cause of the desired charge separation and the photoreduction speed increase. In the following, the resulting compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmittance electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy diffraction X-ray spectroscopy (EDAX) and the Brunauer, Emmett, and Teller (BET) method. Scavenging studies performed in the presence of familiar scavengers confirmed that superoxide radicals (˙O2-) and dissolved oxygen gas have a significant role in the photocatalytic reduction process.

Nanotechnology-assisted treatment of pharmaceuticals contaminated water

The presence of pharmaceutical compounds in wastewater due to an increase in industrialization and urbanization is a serious health concern. The demand for diverse types of pharmaceutical compounds is expected to grow as there is continuous improvement in the global human health standards. Discharge of domestic pharmaceutical personal care products and hospital waste has aggravated the burden on wastewater management. Further, the pharmaceutical water is toxic not only to the aquatic organism but also to terrestrial animals coming in contact directly or indirectly. The pharmaceutical wastes can be removed by adsorption and/or degradation approach. Nanoparticles (NPs), such as 2D layers materials, metal-organic frameworks (MOFs), and carbonaceous nanomaterials are proven to be more efficient for adsorption and/or degradation of pharmaceutical waste. In addition, inclusion of NPs to form various composites leads to improvement in the waste treatment efficacy to a greater extent. Overall, carbonaceous nanocomposites have advantage in the form of being produced from renewable resources and the nanocomposite material is biodegradable either completely or to a great extent. A comprehensive literature survey on the recent advancement of pharmaceutical wastewater is the focus of the present article.

Tailoring Interfacial Physicochemical Properties in Cu2O-TiO2@rGO Heterojunction: Insights from EXAFS and Electron Trap Distribution Analysis

In this study, a solution-based synthesis technique was utilized to produce Cu2O nanoparticles (NPs) on TiO2 nanofibers (TNF), which were then subsequently coated with reduced graphene oxide (rGO) nanosheets. In the absence of any cocatalyst, CTNF@rGO-3% composite displayed an ideal photocatalytic H2 evolution rate of 96 μmol g-1 h-1 under visible light irradiation, this was 10 times higher than that of pure TNF. At 420 nm, the apparent quantum efficiency of this composite reached a maximum of 7.18%. Kelvin probe force microscopy demonstrated the formation of an interfacial electric field that was oriented from CTNF to rGO and served as the driving force for interfacial electron transfer. The successful establishment of an intimate interface between CTNF@rGO facilitated the efficient transfer of charges and suppressed the rate of recombination of photogenerated electron-hole pairs, leading to a substantial enhancement in photocatalytic performance. X-ray photoelectron spectroscopy, photoluminescence spectra, and electrochemical characterization provide further confirmation that formation of a heterojunction between CTNF@rGO leads to an extension in the lifetimes of the photogenerated charge carriers. The experimental evidence suggests that a p-n heterojunction is the mechanism responsible for the significant photocatalytic activity observed in the CTNF@rGO composite during H2 evolution.

Rational design of MOF@COF composites with multi-site functional groups for enhanced elimination of U(VI) from aqueous solution

Both environment and human beings were menaced by the widespread application of radioactive uranium, high-performance and effective elimination of uranium from wastewater is of important meaning for development of environmental sustainability in the future. In this study, the water-stable MOF material and the highly crystalline COF were compounded by a mild hydrothermal strategy, which achieved efficient removal of U(VI) through the synergistic effect. The composites showed the characteristics of both COFs and MOFs, which will possess higher stability, larger surface area and faster adsorption efficiency that cannot be carried out by a single component. Batch experiments and characterizations (SEM, TEM, XRD, FT-IR, BET, XPS, etc.) indicated that UiO-66-NH2@LZU1 had more stable and multi-layer pore structure and rich active functional groups. The Langmuir model and the pseudo-second-order kinetics fitting was more suitable for the U(VI) elimination process. The greatest uranium adsorbing capacity of UiO-66-NH2@LZU1 (180.4 mg g-1) was observed to exceed the UiO-66-NH2 (108.8 mg g-1) and COF-LZU1 (65.8 mg g-1), which reached the excellent hybrid effects. Furthermore, FT-IR and XPS analyses confirmed that the most nitrogen-containing group from COF-LZU1 and oxygen-containing group of UiO-66-NH2 could be combined with U(VI). In addition, electrostatic interaction was also a mechanism during the removal process. This work displayed that UiO-66-NH2@LZU1 was a prospective hybrid material for radioactive waste remediation. The compound method and application mentioned in this work had provided a theoretical basis for designing and developing multi-functional composite adsorbents, which contributed to the development of new materials for radioactive wastewater treatment technologies.

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.

In-situ construction of Zr-based metal-organic framework core-shell heterostructure for photocatalytic degradation of organic pollutants

Photocatalysis is an eco-friendly promising approach to the degradation of textile dyes. The majority of reported studies involved remediation of dyes with an initial concentration ≤50 mg/L, which was away from the existing values in textile wastewater. Herein, a simple solvothermal route was utilized to synthesize CoFe2O4@UiO-66 core-shell heterojunction photocatalyst for the first time. The photocatalytic performance of the as-synthesized catalysts was assessed through the photodegradation of methylene blue (MB) and methyl orange (MO) dyes at an initial concentration (100 mg/L). Under simulated solar irradiation, improved photocatalytic performance was accomplished by as-obtained CoFe2O4@UiO-66 heterojunction compared to bare UiO-66 and CoFe2O4. The overall removal efficiency of dyes (100 mg/L) over CoFe2O4@UiO-66 (50 mg/L) reached >60% within 180 min. The optical and photoelectrochemical measurements showed an enhanced visible light absorption capacity as well as effective interfacial charge separation and transfer over CoFe2O4@UiO-66, emphasizing the successful construction of heterojunction. The degradation mechanism was further explored, which revealed the contribution of holes (h+), superoxide (•O2 -), and hydroxyl (•OH) radicals in the degradation process, however, h+ were the predominant reactive species. This work might open up new insights for designing MOF-based core-shell heterostructured photocatalysts for the remediation of industrial organic pollutants.

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.

Metal-Organic Framework-Based Photocatalysis for Solar Fuel Production

Metal-organic frameworks (MOFs) represent a novel class of crystalline inorganic-organic hybrid materials with tunable semiconducting behavior. MOFs have potential for application in photocatalysis to produce sustainable solar fuels, owing to their unique structural advantages (such as clarity and modifiability) that can facilitate a deeper understanding of the structure-activity relationship in photocatalysis. This review takes the photocatalytic active sites as a particular perspective, summarizing the progress of MOF-based photocatalysis for solar fuel production; mainly including three categories of solar-chemical conversions, photocatalytic water splitting to hydrogen fuel, photocatalytic carbon dioxide reduction to hydrocarbon fuels, and photocatalytic nitrogen fixation to high-energy fuel carriers such as ammonia. This review focuses on the types of active sites in MOF-based photocatalysts and discusses their enhanced activity based on the well-defined structure of MOFs, offering deep insights into MOF-based photocatalysis.

High performance visible light response of a Z-type Bi2WO6/BiOBr/RGO heterojunction photocatalyst for the degradation of norfloxacin

A Bi₂WO₆/BiOBr/RGO (BWO/BOB/RGO) composite photocatalyst with a Z-type heterojunction was prepared by a simple one-pot hydrothermal method, and the micro-morphology and physicochemical properties of the prepared samples were characterized. After reacting under visible light for 120 min, the degradation rate of 20 mg L^-1 norfloxacin (NOR) by BWO/BOB/RGO was 95.12%, and the kinetic constant of the reaction was 6.42 times higher than that of pure BiOBr. Furthermore, BWO/BOB/RGO also shows good recycling stability and universality. The characterization results show that the improvement of the photocatalytic performance of the catalyst is mainly due to the heterojunction formed between Bi₂WO₆, RGO and BiOBr, which enhances the visible light absorption ability, accelerates the photogenerated electron migration and improves the electron-hole pair separation efficiency. The introduction of Bi₂WO₆ and RGO into the catalyst also increased its specific surface area and made it have more surface-active sites. The results of radical capture experiments showed that ˙O₂^- and h⁺ played an important role in the BWO/BOB/RGO reaction system, and the intermediate products and possible degradation pathways of the system were detected and analyzed. Furthermore, the electron transfer mechanism of the Z-type heterojunction using RGO as an electron transport medium and the mechanism of photocatalytic degradation of norfloxacin were proposed.

Recent Advances in Semiconductor Heterojunctions and Z-Schemes for Photocatalytic Hydrogen Generation

The formation of semiconductor heterojunctions and Z-schemes is still a very prominent and efficient strategy of materials chemists to extend the absorption range of semiconductor combinations. Moreover, the spatial separation of photoexcited charge carriers and thereby the reduction of their recombination ultimately lead to increased photocatalytic activities. The present article reviews recent trends in semiconductor heterojunctions and Z-schemes with a focus on hydrogen generation and water splitting, exhibiting specific needs for charge carrier separation. We also included recent material trends, i.e. 2D/2D combinations, direct Z-schemes, MOFs and COFs, and combinations with upconversion materials.

Direct Z-scheme mediated SmVO4/UiO-66-NH2 heterojunction nanocomposite for the degradation of antibiotic tetracycline hydrochloride molecules under sunlight

The use of tetracycline hydrochloride (TCH) for veterinary, human therapy, and agriculture has risen in the past few decades, making it to become one of the most exploited antibiotics. However, TCH residue in the environment is causing issues related to the evolution of antibiotic-resistant bacteria. To address such a problem, photodegradation offers a potential solution to decompose these pollutants in wastewater and thereby mitigates negative environmental impacts. In this context, the research focuses on the use of the rare-earth metal oxide samarium orthovanadate (SmVO₄) with nanorod structure, coupled with UiO-66-NH₂ for the photocatalytic degradation. Their photocatalytic activity to degrade antibiotic TCH molecules is explored under simulated solar light irradiation. The integration of UiO-66-NH₂ with SmVO₄ enhanced the light absorption, recombination resistance, carrier lifetime (from 0.382 to 0.411 ns) and specific surface area (from 67.17 to 246 m²/g) of the composite system as confirmed from multiple analyses. The obtained results further indicated that SmVO₄/UiO-66-NH₂ nanocomposites could form a direct Z-scheme based heterojunction. Such mechanism of charge transfer leads to the effective degradation of TCH molecules up to 50% in 90 min under solar light, while it is degraded only 30% in the case of bare-SmVO₄ nanorods. In this work, the incorporation of UiO-66-NH₂ positively influences photoelectrochemical properties and improves the overall photoredox properties of SmVO₄ for the degradation of complex compounds like antibiotic TCH molecules. Therefore, UiO-66-NH₂ can be proposed as an effective material to sensitize the rare-earth based photocatalytic material.

Metal-Thiolate Framework for Electrochemical and Photoelectrochemical Hydrogen Generation

Hydrogen has evolved as the cleanest and most sustainable fuel, produced directly from naturally abundant water resources. Generation of hydrogen by electrochemical or photoelectrochemical splitting of water has been conceived as the most effective method for hydrogen production. Herein, a robust solid metal-thiolate framework (MTF-1) was obtained by hydrothermal crystallization of the reaction mixture consisting of 1,3,5-triazine-2,4,6-trithioltrisodium salt and Cu^II under mild synthesis conditions. The material was thoroughly characterized and explored as efficient catalyst for electrochemical and photoelectrochemical hydrogen evolution reaction (HER) via water splitting reactions. MTF-1 showed onset potential 0.045 V_RHE and overpotential η(@10 mA cm^-2 ) at 0.096 V_RHE . The electrochemical surface area of MTF-1 was found to be 509 m²  g^-1 . The photo current density at pH 5.0 was found to be 0.487 mA cm^-2 at 0.6 V_RHE . The feasibility of the reaction pathway was correlated from the density function theory study, which suggested the complete downhill energetics indicating spontaneous electrochemical hydrogen generation in the acidic medium.

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.

Design of noble metal-free CoTiO3/Zn0.5Cd0.5S heterostructure photocatalyst for selective synthesis offurfuraldehyde combined withH2production

The development of photocatalytic systems composed of earth-abundant metal-based catalysts for efficient production of clean fuel, H₂ as well as value-added chemicals is of significant importance towards sustainable generation of energy resources. Consequently, herein we report rational construction of Z-scheme CoTiO₃/xZn_0.5Cd_0.5S (x = 5 (S1), 10 (S2), 15 (S3) and 20 wt% (S4)) heterostructures featuring suitable band structure for efficient photocatalytic reduction of protons of water to H₂ combined with selective oxidation of furfuryl alcohol (biomass derivative) to a value-added product, furfuraldehyde. Electron microscopy analysis of heterostructure S2 revealed that Zn_0.5Cd_0.5S nanoparticles are decorated over the surface of CoTiO₃ microrods. The photocatalytic studies showed higher catalytic performance by S2, for selective oxidation of furfuryl alcohol to furfuraldehyde with 95% yield coupled with a H₂ generation rate of 1929 μmol g^-1h^-1 which is about 4-fold higher than that of pristine Zn_0.5Cd_0.5S. The enhanced catalytic performance of heterostructure S2 has been ascribed to synergistic interaction aided by the Z-scheme heterojunction formation between CoTiO₃ and Zn_0.5Cd_0.5S. Overall, this work demonstrates the application of noble metal-free photocatalyst for simultaneous production of H₂ and value-added chemical under mild and environment-friendly conditions.

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.

Pollutant degradation with mediator Z-scheme heterojunction photocatalyst in water: A review

The Z-scheme heterojunction is a photocatalyst with narrow band gap and sufficiently high oxidization and reduction powers for degradation of pollutants in waters. This review firstly summarizes the fundamentals of photocatalysis, and explains the need to develop Z-scheme heterojunctions to harvest energy from sunlight effectively. Secondly, contemporary reports of degradation wastewater pollutants, including organic dyes, antibiotics, and other chemicals are reviewed and discussed. A challenge in the selection of an appropriate Z-scheme for removing a specific pollutant is the lack of available energy levels that are offered by the catalyst and the lack of redox energy levels that are required to break down essential chemical bonds of the pollutants. With reference to the redox energy levels offered by the active photocatalytic species, the redox energy levels of specific pollutants studied in literature are estimated. Challenges and prospects concerning the use of the Z-scheme to degrade recalcitrant pollutants under irradiation by sunlight are outlined at the end of this review.

Black titania an emerging photocatalyst: review highlighting the synthesis techniques and photocatalytic activity for hydrogen generation

The TiO₂ semiconductor photocatalyst is in the limelight of sustainable energy research in recent years because of its beneficial properties. However, its wide band-gap and rapid exciton recombination rate makes it a lame horse, and reduces its photocatalytic efficiency. Recently, researchers have developed facile methods for lowering the band-gap, so that it captures a wide range of solar spectrum, but the efficiency is still way behind the target value. After the discovery of black titania (B-TiO₂), the associated drawbacks of white TiO₂ and its modified forms were addressed to a large extent because it not only absorbs photons in a broad spectral range (UV to IR region), but also modifies the structural and morphological features, along with the electronic properties of the material, significantly boosting the catalytic performance. Hence, B-TiO₂ effectively converts solar energy into renewable chemical energy i.e. green fuel H₂ that can ultimately satisfy the energy crisis and environmental pollution. However, the synthesis techniques involved are quite tedious and challenging. Hence, this review summarizes various preparation methods of B-TiO₂ and the involved characterization techniques. It also discusses the different modification strategies adopted to improve the H₂ evolution activity, and hopes that this review acts as a guiding tool for researchers working in this field.

MOFs-Derived Fusiform In2 O3 Mesoporous Nanorods Anchored with Ultrafine CdZnS Nanoparticles for Boosting Visible-Light Photocatalytic Hydrogen Evolution

The development of efficient visible-light-driven photocatalysts is one of the critically important issues for solar hydrogen production. Herein, high-efficiency visible-light-driven In₂ O₃ /CdZnS hybrid photocatalysts are explored by a facile oil-bath method, in which ultrafine CdZnS nanoparticles are anchored on NH₂ -MIL-68-derived fusiform In₂ O₃ mesoporous nanorods. It is disclosed that the as-prepared In₂ O₃ /CdZnS hybrid photocatalysts exhibit enhanced visible-light harvesting, improves charges transfer and separation as well as abundant active sites. Correspondingly, their visible-light-driven H₂ production rate is significantly enhanced for more than 185 times to that of pristine In₂ O₃ nanorods, and superior to most of In₂ O₃ -based photocatalysts ever reported, representing their promising applications in advanced photocatalysts.

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

Design and facile fabrication of a magnetically separable hetero-structure photocatalyst as well as an adsorbent having dual green benefits towards energy conversion and pollutant remediation are quite indispensable in the current scenario. In this regard, a composite of citrate capped Fe₃O₄ and UiO-66-NH₂ has been designed to remediate Cr (VI) by adsorption and harvest photons from visible light for clean energy (H₂) conversion. The material was prepared by the union of citrate capped Fe₃O₄ (CCM) and versatile aqueous stable Zr-based MOF (UiO-66-NH₂) through in-situ solvothermal method. The composite of CCM with MOF (MU-2) was studied through sophisticated analysis techniques; PXRD, FT-IR, BET, UV-Visible DRS, PL, TG, HRTEM and XPS etc. to reveal the inherent characteristics of the material. BET surface analysis revealed high specific surface area (572.13 m² g^-1) of MU-2 in comparison to its pristine MOF. Furthermore, the dual function composite MU-2's VSM studies showed that its magnetic saturation is 3.07 emu g^-1 that is suitable for magnetic separation after desired reaction from aqueous media. The Cr (VI) sorption studies revealed that the composite adsorbent (MU-2) showed maximum monolayer adsorption capacity (Q_m) of 743 mg g^-1 which followed pseudo second order kinetics. Moreover, the sorption thermodynamics revealed that the process was spontaneous and endothermic in nature. In addition to it, the synthesized composite material displayed enhanced activity towards photocatalytic H₂ evolution with a maximum evolution rate of 417 µmole h^-1 with an apparent conversion efficiency (ACE) of 3.12 %. Typically, MU-2 displays high adsorptions of Cr (VI) as well as some extent of Cr (VI) reduction owning to its populous active sites and free carboxylate groups respectively. Moreover, the synergistic effect of CCM and UNH in the composite resulted in Z scheme mediated charge transfer mechanism that showed enhanced H₂ photo-evolution rates. Hence, MU-2 can be readily utilized as magnetically retrievable dual function composite for Cr (VI) adsorption and photocatalytic H₂ evolution.

Fabrication of size-controlled hierarchical ZnS@ZnIn2S4 heterostructured cages for enhanced gas-phase CO2 photoreduction

Designing and constructing advanced heterojunction architectures are desirable for boosting CO₂ photoreduction performance of semiconductor photocatalysts. Herein, we have prepared hierarchical ZnS@ZnIn₂S₄ core-shell cages with controlled particle sizes using sequential synthesis of Zeolitic imidazolate (ZIF-8) polyhedrons, ZnS cages, and ZnIn₂S₄ nanosheets on the ZnS polyhedron cages. ZIF-8 polyhedrons are firstly synthesized by a liquid-phase approach. The subsequent sulfidation of the ZIF-8 polyhedrons results in the formation of ZnS polyhedron cages, which act as substrates for fabricating ZnS@ZnIn₂S₄ core-shell cages by growing ZnIn₂S₄ nanosheets. The size of ZnS cages can be tuned to optimize CO₂ photoreduction performance of hierarchical ZnS@ZnIn₂S₄ core-shell cages. The synergy of the unique hierarchical core-shell cage-like structure and heterojunction composition endows the hybrid catalyst high incident light utilization, abundant active sites, and effective separation of photoexcited charge carriers. Benefiting from these advantages, the optimized hierarchical ZnS@ZnIn₂S₄ core-shell cages exhibit enhanced performance for CO₂ photoreduction with the CO yield of 87.43 μmol h^-1g^-1 and 84.3% selectivity, which are much superior to those of single ZnIn₂S₄ or ZnS. Upon Au decoration, the CO₂ photoreduction performance of ZnS@ZnIn₂S₄ core-shell cages is further enhanced because of the Schottky junctions and surface plasmon resonance effect.

A review of metal organic framework (MOFs)-based materials for antibiotics removal via adsorption and photocatalysis

Antibiotic abuse has led to serious water pollution and severe harm to human health; therefore, there is an urgent need for antibiotic removal from water sources. Adsorption and photodegradation are two ideal water treatment methods because they are cheap, simple to operate, and reusable. Metal organic frameworks (MOFs) are excellent adsorbents and photocatalysts because of their high porosity, adaptability, and good crystal form. The aim of this study is to suggest ways to overcome the limitations of adsorption and photocatalysis treatment methods by reviewing previous applications of MOFs to antibiotic adsorption and photocatalysis. The different factors influencing these processes are also discussed, as well as the various adsorption and photocatalysis mechanisms. This study provides a valuable resource for researchers intending to use MOFs to remove antibiotics from water bodies.

Rational design of built-in stannic oxide-copper manganate microrods p-n heterojunction for photoelectrochemical sensing of tetracycline

Tetracycline (TC), a popularly found drug pollutant, can be contaminated in food and aquatic regions and causes a severe impact on human health. In this research, a visible light active p-stannic oxide/n-copper manganate (p-SnO₂/n-CuMnO₂) heterojunction was synthesized and has been applied for a signal on photoelectrochemical sensing of antibiotic TC. Firstly, the n-SnO₂ microrods were synthesized via a simple and efficient homogeneous precipitation method and the p-CuMnO₂ nanoparticles were synthesized by a facile ultrasound-assisted hydrothermal method. The SnO₂/CuMnO₂ microrods p-n heterojunction was prepared through a simple impregnation method and physicochemical properties of the microrods are characterized by using X-ray diffraction (XRD), Raman, Brunauer-Emmett-Teller (BET), Fourier-transform infrared (FTIR), UV-Vis diffuse reflectance spectroscopy (UVDRS), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Mott-Schottky analyses. The photoelectrochemical sensing performance of SnO₂/CuMnO₂ microrods was 2.7 times higher than that of as-synthesized pure SnO₂ microrods is due to the more visible light absorption ability and p-n heterojunction (synergy). The designed SnO₂/CuMnO₂/ITO sensor gives photocurrent signals for the detection of TC in the range of 0.01-1000 μM with the detection limit (LOD) of 5.6 nM. The practical applicability of the sensor was monitored in cow milk and the Taipei River water sample.

Ni2P QDs decorated in the multi-shelled CaTiO3 cube for creating inter-shelled channel active sites to boost photocatalytic performance

Control and insight into the abundance of inter-shelled channel active sites and charge transport mechanism are the long-term challenges for enhancing photocatalytic activity. Herein, the Ni₂P quantum dots (QDs) are decorated in the multi-shelled CaTiO₃ cube for creating the abundance of inter-shelled channel active sites, which greatly improve the photocatalytic performances for generating H₂ and degrading tetracycline (TC) relative to pure CaTiO₃ and Ni₂P. Moreover, the Z-scheme mechanism and the quantum effect of the Ni₂P in multi-shelled CaTiO₃ cube play a crucial role for enhancing photocatalytic performance. Furthermore, the photoelectric researches demonstrate that the Ni₂P/CaTiO₃ heterostructure possesses more abundant active sites, smaller interface transmission resistance and faster photo-generated charge transfer efficiency. This work provides a meaningful model to research other materials with creating the abundance of inter-shelled channel active sites for the photo-electrocatalytic field.

Highlights of the characterization techniques on inorganic, organic (COF) and hybrid (MOF) photocatalytic semiconductors

This review is dedicated to the brave COVID warriors fighting against the COVID-2019 pandemic.

Syntheses, design strategies, and photocatalytic charge dynamics of metal–organic frameworks (MOFs): a catalyzed photo-degradation approach towards organic dyes

The presented review focuses on design strategies to develop tailor-made MOFs/CPs of main group, transition and inner-transition elements and their photocatalytic properties to decompose dyes in wastewater discharge and their photocatalytic mechanism.

Metal oxide integrated metal organic frameworks (MO@MOF): rational design, fabrication strategy, characterization and emerging photocatalytic applications

This review focuses on the possible synthesis route, characterization techniques, and mechanistic pathways involved in the photocatalytic applications of MO@MOFs.