Recent advances in core-shell organic framework-based photocatalysts for energy conversion and environmental remediation

Direct conversion of solar energy into chemical energy in an environmentally friendly manner is one of the most promising strategies to deal with the environmental pollution and energy crisis.Among a variety of materials developed as photocatalysts,the core-shell metal/covalent-organic framework(MOF or COF)photocatalysts have garnered significant attention due to their highly porous structure and the adjustability in both structure and functionality.The existing reviews on core-shell organic framework photocatalytic materials have mainly focused on core-shell MOF materials.However,there is still a lack of indepth reviews specifically addressing the photocatalytic performance of core-shell COFs and MOFs@COFs.Simultaneously,there is an urgent need for a comprehensive review encompassing these three types of core-shell structures.Based on this,this review aims to provide a comprehensive understanding and useful guidelines for the exploration of suitable core-shell organic framework photocatalysts towards appropriate photocatalytic energy conversion and environmental governance.Firstly,the classification,synthesis,formation mechanisms,and reasonable regulation of core-shell organic framework were summarized.Then,the photocatalytic applications of these three kinds of core-shell structures in different areas,such as H_(2)evolution,CO_(2)reduction,and pollutants degradation are emphasized.Finally,the main challenges and development prospects of core-shell organic framework photocatalysts were introduced.This review aims to provide insights into the development of a novel generation of efficient and stable core-shell organic framework materials for energy conversion and environmental remediation.

A review on heterogeneous photocatalysis for environmental remediation:From semiconductors to modification strategies

Heterogeneous photocatalysis,an advanced oxidation process,has garnered extensive attention in the field of environmental remediation because it involves the direct utilization of solar energy for the removal of numerous pollutants.However,the application of heterogeneous photocatalysis in environmental remediation has not achieved the expected consequences due to enormous challenges such as low photocatalytic efficiencies and high costs of heterogeneous photocatalysts in large-scale practical applications.Furthermore,pollutants in the natural environment,including water,air,and solid phases,are diverse and complex.Therefore,extensive efforts should be made to better understand and apply heterogeneous photocatalysis for environmental remediation.Herein,the fundamentals of heterogeneous photocatalysis for environmental remediation are introduced.Then,potential semiconductors and their modification strategies for environmental photocatalysis are systematically presented.Finally,conclusions and prospects are briefly summarized,and the direction for the future development of environmental photocatalysis is explored.This review may provide reference directions toward understanding,researching,and designing photocatalytic remediation systems for various environmental pollutants.

Bio/hydrochar Sorbents for Environmental Remediation

A rising global population and aspirational higher living standards has driven a step change in resource utilization and concomitant anthropogenic pollution across the biosphere.Low-cost and scalable technologies for environmental remediation are therefore urgently sought,with an emphasis on trash-to-treasure strategies that exploit abundant but underutilized waste by-products of existing sectors.Biochars are carbon-rich,porous solids produced by biomass pyrolysis under anaerobic or oxygen-scarce conditions at high temperature(350–700°C),while hydrochars are produced by hydrothermal biomass carbonization at lower temperature(130–250°C)and high autogenous pressures(0.3–4.0 MPa).Bio/hydrochars possess unique physicochemical properties,notably high surface areas(100–1500 m2 g-1)and porosity(0.25–2.5 cm^(3)g^(-1))and rich surface chemistry featuring carboxylic,phenolic,hydroxyl,and carbonyl functions,amenable to chemical,physical,or biochemical modification,rendering them ideal sorbents for pollutants such as heavy metals(e.g.As and Cr),and toxic organic(e.g.,dyes and xenobiotics)and inorganic(e.g.,SO_(2))molecules.Bio/hydrochars are attractive for environmental remediation of pollutant mixtures by surface complexation,redox chemistry,electrostatic interactions/ion exchange,or coprecipitation.This review discusses recent opportunities and challenges in creating bio/hydrochar sorbents and their nanocomposites through grafting,doping,and chemical/physical activation,for the depollution of aquatic and atmospheric environments.

Electrospun Semiconductor-Based Nano-Heterostructures for Photocatalytic Energy Conversion and Environmental Remediation:Opportunities and Challenges

Harvesting solar energy to drive the semiconductor photocatalysis offers a promising tactic to address ever-growing challenges of both energy shortage and environmental pollution.Design and synthesis of nano-heterostructure photocatalysts with controllable components and morphologies are the key factors for achieving highly efficient photocatalytic processes.Onedimensional(1D)semiconductor nanofibers produced by electrospinning possess a large ratio of length to diameter,high ratio of surface to volume,small grain sizes,and high porosity,which are ideally suited for photocatalytic reactions from the viewpoint of structure advantage.After the secondary treatment of these nanofibers through the solvothermal,gas reduction,in situ doping,or assembly methods,the multi-component nanofibers with hierarchical nano-heterostructures can be obtained to further enhance their light absorption and charge carrier separation during the photocatalytic processes.In recent years,the electrospun semiconductorbased nano-heterostructures have become a“hot topic”in the fields of photocatalytic energy conversion and environmental remediation.This review article summarizes the recent progress in electrospinning synthesis of various kinds of high-performance semiconductor-based nano-heterostructure photocatalysts for H2 production,CO_(2) reduction,and decomposition of pollutants.The future perspectives of these materials are also discussed.

Bio-capped and green synthesis of ZnO/g-C_(3)N_(4) nanocomposites and its improved antibiotic and photocatalytic activities: An exceptional approach towards environmental remediation

In this research study, we have synthesized the bio-capped ZnO/g-C_(3)N_(4) nanocomposites by employing lemon juice(Citrus limon) as a stabilizer and mediator. Fruitfully, lemon juice which contains various acidic functional groups and citric acid has the capability to block the surface of g-C_(3)N_(4) from chemical reactivity and activated the surface of g-C_(3)N_(4) for various reactions. Consequently, the agglomeration behavior and controlled shape of g-C_(3)N_(4) has also been achieved. Our experimental results i.e. XRD,TEM, HRTEM, PL, FS, XPS, and PEC have confirmed that the lemon juice mediated and green g-C_(3)N_(4)(L-CN) have good performances and remarkable visible light photocatalytic activities as compared to the chemically synthesized g-C_(3)N_(4)(CN). Furthermore, the small surface area and low charge separation of g-C_(3)N_(4) is upgraded by coupling with Zn O nanoparticles. It is proved that the coupling of Zn O worked as a facilitator and photoelectron modulator to enhance the charge separation of g-C_(3)N_(4). Compared to pristine lemon-mediated green g-C_(3)N_(4)(L-CN), the most active sample 5Zn O/L-CN showed ~ 5-fold improvement in activities for ciprofloxacin(CIP) and methylene blue(MB) degradation. More specifically,the mineralization process and degradation pathways, and the mineralization process of ciprofloxacin(CIP) and methylene blue(MB) are suggested. Finally, our present novel research work will provide new access to synthesize the eco-friendly and bio-caped green g-C_(3)N_(4)nanomaterials and their employment for pollutants degradation and environmental purification.

Current Research and Strategy on the Biosurfactants Used in the Remediation of Petrochemical Polluted Environment

Biosurfactants are biologically active metabolites, and the efficiency of direct screening of new biosurfactants from nature using traditional methods is low, which should be enhanced in the following studies by adopting advanced biotechnologies. Rapid development and wide application of microbial culture independent methods, such as metagenomics, metatranscriptomics, metaproteomics and metabonomics, etc., contributes to quickly and precisely screening of novel biological surfactants. We mainly represented the current status of research and applications of biosurfactants in the remediation of petrochemical polluted environment, and also prospected avenues for future research.

Integrated bioremediation techniques in a shrimp farming environment under controlled conditions

This study investigated the integrated bioremediation techniques for a shrimp culture system to reduce unconsumed feed and the contents of suspended solids（SS）, nutrients and organic pollutants using barracuda,clamworm, scallop, large algae and a biofilter. A multi-pool internal circulation system was designed to test the effectiveness of the techniques in the laboratory. The experimental result has shown that Argopecten irradians,Gracilaria lemaneiformis and the biofilter efficiently reduced the contents of SS, dissolved inorganic carbon（DIC）and dissolved organic carbon（DOC） in the breeding wastewater. The amount of unconsumed feed was significantly reduced by barracuda and clamworm, but there was an increase in the contents of SS, DIC and DOC in the water due to disturbance by the barracuda and clamworm. The capacity of macroalgae to extract inorganic nitrogen was insufficient. However, the balance of the nitrogen fixation rate of macroalgae and the biological exhaust nitrogen rate within the system should be fully considered. The use of the biofilter alone was not optimal for the remediation of organic matter in shrimp effluent so that auxiliary foam separation technology is needed to improve the ability of the system to remove macromolecules. This study provides a basis for the further development of remediation techniques to reduce the environmental impact of shrimp aquaculture.

Research on the Progress of Environmental Remediation Methodologies under the Conditions of Oil and Heavy Metal Pollution

In this paper, we conduct research on the progress of environmental remediation methodologies under the conditions of oil and heavy metal pollution. The main repair contaminated soil measures include chemical, physical and chemical measures, biological repair measures and agricultural ecological measures, engineering measures, etc. Selection principle is to adjust measures to local conditions, at the same time, take the technical, economic and effects of factors such as accessibility. After comparing the mentioned techniques, we conclude that the bioremediation method holds the best effectiveness for us to make contribution to the environmental protection. In final part, we give the conclusion and sct up the prospect.

3D-Printed MOF Monoliths:Fabrication Strategies and Environmental Applications

Metal-organic frameworks(MOFs)have been extensively considered as one of the most promising types of porous and crystalline organic-inorganic materials,thanks to their large specific surface area,high porosity,tailorable structures and compositions,diverse functionalities,and well-controlled pore/size distribution.However,most developed MOFs are in powder forms,which still have some technical challenges,including abrasion,dustiness,low packing densities,clogging,mass/heat transfer limitation,environmental pollution,and mechanical instability during the packing process,that restrict their applicability in industrial applications.Therefore,in recent years,attention has focused on techniques to convert MOF powders into macroscopic materials like beads,membranes,monoliths,gel/sponges,and nanofibers to overcome these challenges.Three-dimensional(3D)printing technology has achieved much interest because it can produce many high-resolution macroscopic frameworks with complex shapes and geometries from digital models.Therefore,this review summarizes the combination of different 3D printing strategies with MOFs and MOF-based materials for fabricating 3D-printed MOF monoliths and their environmental applications,emphasizing water treatment and gas adsorption/separation applications.Herein,the various strategies for the fabrication of 3D-printed MOF monoliths,such as direct ink writing,seed-assisted in-situ growth,coordination replication from solid precursors,matrix incorporation,selective laser sintering,and digital light processing,are described with the relevant examples.Finally,future directions and challenges of 3D-printed MOF monoliths are also presented to better plan future trajectories in the shaping of MOF materials with improved control over the structure,composition,and textural properties of 3D-printed MOF monoliths.

Micro-nano-fabrication of green functional materials by multiphase microfluidics for environmental and energy applications

Multiphase microfluidic has emerged as a powerful platform to produce novel materials with tailor-designed functionalities,as microfluidic fabrication provides precise controls over the size,component,and structure of resultant materials.Recently,functional materials with well-defined micro-/nanostructures fabricated by microfluidics find important applications as environmental and energy materials.This review first illustrated in detail how different structures or shapes of droplet and jet templates are formed by typical configurations of microfluidic channel networks and multiphase flow systems.Subsequently,recent progresses on several representative energy and environmental applications,such as water purification,water collecting and energy storage,were overviewed.Finally,it is envisioned that integrating microfluidics and other novel materials will play increasing important role in contributing environmental remediation and energy storage in near future.

Recent advances in bismuth-based photocatalysts:Environment and energy applications

Photocatalysis is an effective way to solve the problems of environmental pollution and energy shortage.Numerous photocatalysts have been developed and various strategies have been proposed to improve the photocatalytic performance.Among them,Bi-based photocatalysts have become one of the most popular research topics due to their suitable band gaps,unique layered structures,and physicochemical properties.In this review,Bi-based photocatalysts(BiOX,BiVO_(4),Bi_(2)S_(3),Bi_(2)MoO_(6),and other Bi-based photocatalysts)have been summarized in the field of photocatalysis,including their applications of the removal of organic pollutants,hydrogen production,oxygen production etc.The preparation strategies on how to improve the photocatalytic performance and the possible photocatalytic mechanism are also summarized,which could supply new insights for fabricating high-efficient Bi-based photocatalysts.Finally,we summarize the current challenges and make a reasonable outlook on the future development direction of Bi-based photocatalysts.

Photoelectrocatalytic principles for meaningfully studying photocatalyst properties and photocatalysis processes:From fundamental theory to environmental applications

Photocatalysis is critically important for environmental remediation and renewable energy technologies.The ability to objectively characterize photocatalyst properties and photocatalysis processes is paramount for meaningful performance evaluation and fundamental studies to guide the design and development of high-performance photocatalysts and photocatalysis systems.Photocatalysis is essentially an electron transfer process,and photoelectrocatalysis(PEC)principles can be used to directly quantify transferred electrons to determine the intrinsic properties of photocatalysts and photocatalysis processes in isolation,without interference from counter reactions due to physically separated oxidation and reduction half-reactions.In this review,we discuss emphatically the PEC-based principles for characterizing intrinsic properties of photocatalysts and important processes of photocatalysis,with a particular focus on their environmental applications in the degradation of pollutants,disinfection,and detection of chemical oxygen demand(COD).An outlook towards the potential applications of PEC technique is given.

A Review of Metal–Organic Framework-Based Compounds for Environmental Applications

Metal–organic framework-based compounds have recently gained great attention because of their unique porous structure,ordered porosity,and high specific surface area.Benefiting from these superior properties,metal–organic framework-based compounds have been proven to be one of the most potential candidates for environmental governance and remediation.In this review,the different types of metal–organic framework-based compounds are first summarized.Further,the various environmental applications of metal–organic framework-based compounds including organic pollutant removal,toxic and hazardous gas capture,heavy metal ion detection,gas separation,water harvesting,air purification,and carbon dioxide reduction reactions are discussed in detail.In the end,the opportunities and challenges for the future development of metal–organic framework-based compounds for environmental applications are highlighted.

Advancements in S-scheme heterojunction materials for photocatalytic environmental remediation

Recently,S-scheme heterojunctions have gained considerable attention in the field of photocatalytic environmental remediation as their potential to achieve efficient spatial charge separation coupled with strong redox capacities.Herein,this review provides an overview of the current state-of-the-art in the development of S-scheme-based photocatalysts for the purification of environmental contaminants.The review first covers the fundamentals of heterogeneous photocatalysis for environmental purification.Subsequently,an introduction to the background,mechanism,design principles,and characterization techniques of S-scheme heterojunctions is presented.Then,the review presents a comparison and summary of using various S-scheme photocatalysts for the removal of several target pollutants,such as bacteria,heavy metals,nitrogen oxides,antibiotics,and phenols.Additionally,the modification strategies of S-scheme heterojunction photocatalysts are also provided.Finally,a brief discussion of the challenges and prospects associated with S-scheme photocatalytic systems is demonstrated.

A review on Bi_(2)WO_(6)-based photocatalysts synthesis, modification, and applications in environmental remediation, life medical, and clean energy

Photocatalysis has emerged a promising strategy to remedy the current energy and environmental crisis due to its ability to directiy convert clean solar energy into chemical energy.Bismuth tungstate(Bi_(2)WO_(6))has been shown to be an excellent visible light response,a well-defined perovskite crystal structure,and an abundance of oxygen atoms(providing efficient channels for photogenerated carrier transfer)due to their suitable band gap,effective electron migration and separation,making them ideal photocatalysts.It has been extensively applied as photocatalyst in aspects including pollutant removal,carbon dioxide reduction,solar hydrogen production,ammonia synthesis by nitrogen photocatalytic reduction,and cancer therapy.In this review,the fabrication and application of Bi_(2)WO_(6) in photocatalysis were comprehensively discussed.The photocatalytic properties of BizwO-based materials were significantly enhanced by carbon modification,the construction of heterojunctions,and the atom doping to improve the photogenerated carrier migration rate,the number of surface active sites,and the photoexcitation ability of the composites.In addition,the potential development directions and the existing challenges to improve the photocatalytic performance of Bi_(2)WO_(6)-based materials were discussed.

Rare earth element-modified MOF materials:synthesis and photocatalytic applications in environmental remediation

Metal-organic framework-like materials(MOFs)have been developed in the fields of photocatalysis for their excellent optical properties and physicochemical properties,including environmental remediation,CO_(2)photoreduction,water splitting,and so on.With their important roles in various fields,rare earth elements have received growing interests from scientists.Modifying MOFs with rare earth elements for modification allows broadening the absorption spectrum,while the active electrons on their empty 4f orbitals can act as traps to capture photoexcited carriers to inhibit the recombination of electron-hole pairs,thus promoting photocatalytic activity.Therefore,rare earth elements modified MOFs provide an attractive way to achieve their high value utilization.In this mini-review,the synthesis of rare earth element-modified MOFs photocatalysts and corresponding applications in the removal of antibiotics,CO_(2)reduction,and hydrogen production are constructively summarized and discussed.Finally,the latest advancements and current difficulties of these materials as well as the application prospects are also provided.

Application of clay minerals as adsorbents for removing heavy metals from the environment

The harmful effects of heavy metals on the environment have attracted considerable attention.Adsorption is an effective method for removing heavy metals from water and soil.Clay minerals are abundant in the environment and have the advantages of a wide range of sources,low cost,and renewability.Clay minerals can be used as adsorbents to achieve the effective removal of heavy metals.In this review,clay minerals are systematically classified based on crystal interlayer structure,molecular structure,and corresponding physical and chemical properties.Then,the adsorption effects of clay minerals as adsorbents on common heavy metals in the environment are summarized,and the adsorption performance of modified clay minerals on heavy metals is improved.Finally,the experimental studies using clay minerals as adsorbents for soil groundwater remediation are summarized.In addition,clay minerals are not only used in the field of heavy metal adsorption and removal but also act as ideal catalysts and catalyst carrier materials.This review provides some references for the further applications of clay minerals in the field of environmental remediation and actual industry.

Transparent Coating with TiO2 Nanorods for High-performance Photocatalytic Self-cleaning and Environmental Remediation

High-performance self-cleaning coatings are highly desired by the industry and market.Herein,we synthesized two kinds of ultrafine TiO2 nanocrystals,one is anatase dots with a diameter of 5 nm,and the other is rutile rods with 1.5 nm in width and 7 nm in length.The prepared TiO:nanocrystal is highly dispersed and stable in water over a month.The coating can be fabricated via a simple spraving method,displaying excellent optical properties and photocatalytic performance on self-cleaning and surrounding environment remediation.The transmittance of glass remains 80%-90%for visible and near-infrared light after 30 cycles of spray.RhB solution(50 mg/L)was applied to the coating surface and form a solid RhB layer was formed,which can be completely removed in 30 min's light irradiation.RhB aqueous solution(100 mL,5 mg/L)was purified after 180 min by a 10 cm×10 cmglass,on which the coating was sprayed 30 times.The concentrations of formaldehyde and PM2.5 in surrounding air displayed a significant decrease along 50 min's monitoring.This high-performance coating shows great potential for constructing functional coating on various substrates for industrial applications.

Leaching behaviors of calcium and magnesium in ion-adsorption rare earth tailings with magnesium sulfate

The leaching behaviors of calcium and magnesium in the rare earth tailings leached with magnesium sulfate using deionized water,CaCl2 solution and lime water were investigated.Experimental data indicated that magnesium in the tailings was easy to be leached out since most of the magnesium was in the form of water-soluble phase.Most of calcium in the lime water was electrostatically adsorbed on the clay mineral of the tailings,and the water-soluble magnesium was also gradually converted into exchangeable phase because of back-adsorption of Mg2+on the clay mineral with increasing the pH values.When the liquid-to-solid ratio was 0.80,the contents of readily-available magnesium and calcium were 104.4−207.6 and 201.7−1426.3 mg/kg,respectively,which could meet the requirements for plants.These results suggest a promising route for the environmental remediation of ion-adsorption rare earth ore after in-situ leaching.

Palladium nanoparticles assembled on titanium nitride for enhanced electrochemical hydrodechlorination of 2,4-dichlorophenol in water

We report a one‐pot surfactant‐free wet‐chemical reduction approach to the synthesis of palladium/titanium nitride(Pd/TiN)and Pd/carbon(Pd/C)composites,in which^5 nm Pd NPs were uniformly dispersed on TiN or C.In terms of catalytic performance,Pd/TiN showed enhanced efficiency and stability compared with those of Pd/C and bare TiN in the electrocatalytic hydrodechlorination(EHDC)reaction of 2,4‐dichlorophenol(2,4‐DCP)in aqueous solution.The superior performance of Pd/TiN arises from the promotion effect of TiN.Strong metal‐support interactions modified the electronic structure of Pd,which optimized generation of H*ads and 2,4‐DCP adsorption/activation.The cathode potential plays a vital role in controlling the EHDC efficiency and the product distribution.A working potential of?0.80 V was shown to be optimal for achieving the highest EHDC efficiency and maximizing conversion of 2,4‐DCP to phenol(P).Our studies of the reaction pathway show that EHDC of 2,4‐DCP on Pd/TiN proceeded by 2,4‐DCP→p‐chlorophenol(p‐CP),o‐chlorophenol(o‐CP)→P;however,Pd/TiN presented little selectivity for cleavage of p‐C‐Cl vs o‐C‐Cl.This work presents a new approach to enhancing Pd performance towards EHDC through the effects of a support.The strategy demonstrated here could also be extended to design highly efficient catalysts for other hydrogenation reactions.