Efficient photocatalytic nitrogen fixation via oxygen vacancies in Zr-MOFs at ambient conditions

Photocatalytic nitrogen fixation is seen to be a potential technology for nitrogen reduction due to its eco-friendliness, low energy consumption, and environmental protection. In this study, photocatalysts with abundant oxygen vacancies (Zr-naphthalene dicarboxylic acid (Zr-NDC) and Zr-phthalic acid (Zr-BDC)) were designed using 1,4-naphthalene dicarboxylic acid (H2NDC) and 1,4-phthalic acid (H2BDC) as ligands. Since the structure of H2NDC includes one extra benzene ring than H2BDC, the charge density differential of the organic ligand is probably altered. The hypothesis is proved by density function theory (DFT) calculation. The abundant oxygen vacancies of the catalyst offer numerous active sites for nitrogen fixation. Concurrently, the process of ligand-metal charge transfer facilitates photo-electron transfer, creating an active center for nitrogen reduction. Additionally, the functionalization of ligand amplifies another pathway for charge transfer, broadening the light absorption range of Metal-organic framework (MOF) and increasing its capacity for nitrogen reduction. In contrast to H2BDC, the benzene ring added in H2NDC structure acts as an electron energy storage tank with a stronger electron density difference favorable for photogenerated electron-hole separation resulting in higher photocatalytic activity in Zr-NDC. The experimental results show that the nitrogen fixation efficiency of Zr-NDC is 163.7 µmol g-1h-1, which is significantly better than that of Zr-BDC (29.3 µmol g-1h-1). This work utilizes cost-effective and non-toxic ingredients to design highly efficient photocatalysts, thereby significantly contributing to the practical implementation of green chemistry principles.

Comprehensive spectroscopy and photocatalytic activity analysis of TiO2-Pt systems under LED irradiation

This study presents a thorough spectroscopic analysis of TiO2-Pt systems under LED irradiation, with a focus on elucidating the photodeposition process of Pt nanoparticles onto TiO2 surfaces. The methodology leverages an innovative LED photoreactor tailored to a specific spectral range, enabling precise characterization of the excitation spectrum of TiO2-Pt composites. Through the identification of Pt precursor species and their excitation under LED-UV light, a photodeposition mechanism is proposed involving concurrent excitation of both the TiO2 semiconductor and the H2PtCl6 precursor. The LED photoreactors are employed to scrutinize the excitation profile of TiO2-Pt materials, revealing that the incorporation of Pt nanoparticles does not expand TiO2's absorption spectrum. Furthermore, UV-A exposure in the absence of Pt did not induce the formation of surface defects, underscoring the lack of visible light activity in TiO2-Pt systems. Spectroscopic analyses, complemented by naproxen photooxidation experiments, indicate the absence of a significant plasmonic effect in Pt nanoparticles within the experimental framework. Mass spectroscopy results corroborate the presence of distinct naproxen degradation pathways, suggesting minimal influence from photocatalyst properties. This research provides a detailed spectroscopic insight into TiO2-Pt photocatalysis, enriching the knowledge of photocatalytic materials in LED lighting.

Magnetic cobalt metal organic framework for photocatalytic water splitting hydrogen evolution

Using water as a renewable and safe energy source for hydrogen generation has reduced the need to use toxic fossil fuels. Photocatalytic approaches provide a worthy solution to avoid the high expenditure on complicated electrochemical pathways to promote Hydrogen Evolution Reactions. However, several types of photocatalysts including noble metal-based catalysts have already been in use for this purpose, which are generally considered high-cost as well. The present study aims to use the benefits of metal-organic frameworks (MOFs) with semiconductor-like characteristics, highly porous structures and high design flexibility. These properties of MOFs allow more efficient and effective mass transport as well as exposure to light.in this paper, using MOF technology and benefiting from the characteristics of Fe3O4 nanoparticles as catalyst support for more efficient separation of catalyst, we have synthesized a novel composite. Our proposed photocatalyst demonstrates efficient harvest of light in all wavelengths from UV to visible to generate electron/hole pairs suitable for water splitting with a turnover frequency of 0.222 h-1 at ambient conditions without requiring any additives.

Bimetallic Porphyrin-Based Metal-Organic Framework as a Superior Photocatalyst for Enhanced Photocatalytic Hydrogen Production

The meaningful and rational engineering of porphyrin-based catalysts with multimetallic active sites is very attractive toward photocatalytic hydrogen generation from water decomposition. Herein, three metal organic frameworks (MOFs) based on meso-tetrakis(4-carboxylphenyl)porphyrin (TCPP) were successfully constructed under solvothermal conditions. As a novel architectured photocatalyst (triclinic, C48H29N4O10PdYb), Pd/Yb-PMOF manifested diverse metal active sites, suitable bandgap positions, prominent visible light-collecting capacity, excellent carrier transfer efficiency, and obvious synergistic effect between ytterbium and palladium ions. Consequently, such a bimetallic MOF exhibited strengthened photocatalytic hydrogen evolution performance. Concretely, its hydrogen generation efficiency was up to 3196.42 μmol g-1 h-1 with 2 wt % Pt as a cocatalyst under visible light illumination. Our work demonstrates a promising strategy for highly efficient visible-light catalysts based on bimetallic-trimmed porphyrin MOFs.

Eosin Y-Based Metal-Organic Framework Synergistic with Cobalt(II) Complex for Hydrogen Evolution through Photoinduced Intermolecular Electron Transfer

Photocatalytic hydrogen evolution reaction (HER) is a promising approach for producing clean energy and has the potential to play an important role in the transition toward a more sustainable and environmentally friendly energy system. Optimizing the photoinduced electron transfer (PET) process and increasing visible-light utilization play a central role in photocatalysis. Herein, we built a novel Eosin Y-based metal-organic framework (Zn-EYTP) by synergizing a cobalt(II) complex for boosting the H2 evolution efficiency through photoinduced intermolecular electron transfer. Under optimized conditions, the maximum H2 evolution efficiency for Zn-EYTP was determined to be a turnover number (TON) value of 11,100 under green LED irradiation. And the synthesized Zn-EYTP photocatalysts could be easily recycled to restore the initial photocatalytic activity even after 3 cycles. Detailed studies reveal that the significantly enhanced HER activity in Zn-EYTP could be ascribed to the effective separation of photogenerated charges and the synergistic intermolecular interaction between Zn-EYTP and [Co(bpy)3]Cl2. The present work enables a deeper understanding of the importance of the PET process for enhanced HER photocatalytic activities, which will provide a viable strategy for the development of highly efficient photocatalysts.

A ratiometric fluorescent paper sensor based on dye-embedded MOF for high-sensitive detection of arginine

Ratiometric fluorescent sensors can suppress the interference of factors unrelated to analysis due to their built-in self-calibration characteristics, which exhibit higher sensitivity and more obvious visual detection in the process of qualitative and quantitative analysis. Herein, we constructed a ratiometric fluorescence probe based on fluorescent/colorimetric dual-mode method for the determination of arginine by encapsulating rhodamine B in-situ into UiO-66-NH2 MOFs (UiO-66-NH2@RhB). The as-prepared probe showed dual-emission characteristics under a single excitation wavelength. The fluorescence intensity of UiO-66-NH2 was increased significantly by arginine, while the emission peak intensity of rhodamine B remained stable, resulting in a single-signal response with fixed reference. Furthermore, the practicality of the presented sensor was successfully validated by quantitative detection of arginine in human serum. More significantly, paper-based sensors for arginine detection were devised by using carboxymethyl cellulose modified filter papers. Under the irradiation of ultraviolet light, the paper-based sensors would produce obvious color variation from lightpink to bluish violet. This work provided a convenient and efficient method for on-site detection of arginine.

A heterostructural MoS2QDs@UiO-66 nanocomposite for the highly efficient photocatalytic degradation of methylene blue under visible light and simulated sunlight

The development of recyclable photocatalysts with high activity and stability has piqued the interest of researchers in the field of wastewater treatment. In this study, an ultrasonic probe approach was used to immerse a sequence of heterojunctions formed by metal-organic frameworks (UiO-66) and different amounts of molybdenum disulfide quantum dots (MoS2QDs), resulting in a highly recyclable MoS2QDs@UiO-66 photocatalyst. Multiple advanced techniques, such as XPS, XRD, TEM, XRF, and UV-vis spectrophotometry, were used to characterize and confirm the successful preparation of UIO-66 impregnated with MoS2QDs. The results indicated that the best heterostructure catalyst exhibited superior efficiency in the photocatalytic degradation of methylene blue (MB) in water, achieving approximately 99% removal within 30 minutes under simulated sunlight, while approximately 97% removal under visible light. The outstanding photocatalytic performance is predominantly attributed to the photoinduced separation of carriers in this heterostructure system. This study proposes a unique, simple, and low-cost method for improving the degradation performance of organic contaminants in water.

Modulating Photoinduced Electron Transfer between Photosensitive MOF and Co(II) Proton Reduction Sites for Boosting Photocatalytic Hydrogen Production

Photocatalytic hydrogen production via water splitting is the subject of intense research. Photoinduced electron transfer (PET) between a photosensitizer (PS) and a proton reduction catalyst is a prerequisite step and crucial to affecting hydrogen production efficiency. Herein, three photoactive metal-organic framework (MOF) systems having two different PET processes where PS and Co(II) centers are either covalently bonded or coexisting to drive photocatalytic H2 production are built. Compared to these two intramolecular PET systems including CoII -Zn-PDTP prepared from the post-synthetic metalation toward uncoordinated pyridine N sites of Zn-PDTP and sole cobalt-based MOF Co-PDTP, the CoII (bpy)3 @Zn-PDTP system impregnated by molecular cocatalyst possessing intermolecular PET process achieves the highest H2 evolution rate of 116.8 mmol g-1 h-1 over a period of 10 h, about 7.5 and 9.3 times compared to CoII -Zn-PDTP and Co-PDTP in visible-light-driven H2 evolution, respectively. Further studies reveal that the enhanced photoactivity in CoII (bpy)3 @Zn-PDTP can be ascribed to the high charge-separation efficiency of Zn-PDTP and the synergistic intermolecular interaction between Zn-PDTP and cobalt complexes. The present work demonstrates that the rational design of PET process between MOFs and catalytic metal sites can be a viable strategy for the development of highly efficient photocatalysts with enhanced photocatalytic activities.

Photo-Induced Active Lewis Acid-Base Pairs in a Metal-Organic Framework for H2 Activation

The establishment of active sites as the frustrated Lewis pair (FLP) has recently attracted much attention ranging from homogeneous to heterogeneous systems in the field of catalysis. Their unquenched reactivity of Lewis acid and base pairs in close proximity that are unable to form stable adducts has been shown to activate small molecules such as dihydrogen heterolytically. Herein, we show that grafted Ru metal-organic framework-based catalysts prepared via N-containing linkers are rather catalytically inactive for H2 activation despite the application of elevated temperatures. However, upon light illumination, charge polarization of the anchored Ru bipyridine complex can form a transient Lewis acid-base pair, Ru+-N- via metal-to-ligand charge transfer, as confirmed by time-dependent density functional theory (TDDFT) calculations to carry out effective H2-D2 exchange. FTIR and 2-D NMR endorse the formation of such reactive intermediate(s) upon light irradiation.

Tunable Photocatalytic Singlet Oxygen Generation by Metal-Organic Frameworks via Functionalization of Pyrene-Containing Linkers

Metal-organic frameworks (MOFs) are highly versatile materials that have shown great promise in chemical warfare agent (CWA) adsorption and decontamination. Sulfur mustard has been one of the most prominently used CWAs over the last century; therefore, the development of effective detoxification strategies is of utmost importance. However, typical routes of detoxification are slow and/or result in the production of harmful byproducts. NU-1000 has previously shown promise as a "soft" oxidizer that can readily detoxify sulfur mustard and its simulant 2-chloroethyl ethyl sulfide (2-CEES) through the generation of singlet oxygen in the presence of either UV (396 nm) or blue (465 nm) light. Several variants of NU-1000 were synthesized (MOF-R, R = -Cl, -NO2, -CH3) with functional groups positioned either ortho or meta to the carboxylic acid on the linker. NU-1000-o-(Cl)4 and NU-1000-m-(Cl)4 showed significant enhancement of photooxidation of 2-CEES due to spin-orbit coupling, enhancing the intersystem crossing into the MOF triplet (T1) state. Furthermore, substitution of MOF linkers led to pyrene-phenyl rotation. Linkers with substituents in the ortho-position were shown to have smaller pyrene-phenyl torsion angles, leading to enhanced conjugation between the rings and a subsequent red shift in the absorption spectra. This red shift leads to enhanced reactivity of NU-1000-o-(Cl)4 under blue light conditions and gives perspective on making materials with enhanced reactivity utilizing visible light.

Confinement of Organic Dyes in UiO-66-Type Metal-Organic Frameworks for the Enhanced Synthesis of [1,2,5]Thiadiazole[3,4-g]benzoimidazoles

Organic dyes as non-noble metal photosensitizers have attracted increasing attention due to their environmental friendliness and sustainability but suffer from fast deactivation and low stability. Here, we reported a fruitful strategy by the confinement and stabilization of visible light-active signal unit organic dyes within the metal-organic frameworks (MOFs) and developed a series of heterogeneous photocatalysts dye@UiO-66s [dye = fluorescein (FL)/rhodamine B (RhB)/eosin Y (EY), UiO-66s = UiO-66, and Bim-UiO-66]. It has been demonstrated that the encapsulated dyes can effectively sensitize MOF hosts and dominate the band structures and photocatalytic activities of dye@UiO-66s regardless of the ligand functionalization of MOFs. Photocatalytic experiments showed that these dye@UiO-66s exhibit enhanced activities relative to free dyes and among them, FL@Bim-UiO-66 displays excellent efficiencies toward the green synthesis of new carbon-bridged annulations, [1,2,5]thiadiazole[3,4-g]benzoimidazoles in the yield of up to 98% at room temperature with outstanding stability and reusability. Furthermore, the intramolecular cyclization intermediate was captured and characterized by the single-crystal X-ray diffraction analysis.

Defined metal atom aggregates precisely incorporated into metal-organic frameworks

Nanosized metal aggregates (MAs), including metal nanoparticles (NPs) and nanoclusters (NCs), are often the active species in numerous applications. In order to maintain the active form of MAs in "use", they need to be anchored and stabilised, preventing agglomeration. In this context, metal-organic frameworks (MOFs), which exhibit a unique combination of properties, are of particular interest as a tunable and porous matrix to host MAs. A high degree of control in the synthesis towards atom-efficient and application-oriented MA@MOF composites is required to derive specific structure-property relationships and in turn to enable design of functions on the molecular level. Due to the versatility of MA@MOF (derived) materials, their applications are not limited to the obvious field of catalysis, but increasingly include 'out of the box' applications, for example medical diagnostics and theranostics, as well as specialised (bio-)sensoring techniques. This review focuses on recent advances in the controlled synthesis of MA@MOF materials en route to atom-precise MAs. The main synthetic strategies, namely 'ship-in-bottle', 'bottle-around-ship', and approaches to achieve novel hierarchical MA@MOF structures are highlighted and discussed while identifying their potential as well as their limitations. Hereby, an overview of standard characterisation methods that enable a systematic analysis procedure and state-of-art techniques that localise MA within MOF cavities are provided. While the perspectives of MA@MOF materials in general have been reviewed various times in the recent past, few atom-precise MAs inside MOFs have been reported so far, opening opportunities for future investigation.

Metal-Organic Frameworks as Photocatalysts for Solar-Driven Overall Water Splitting

Metal-organic frameworks (MOFs) have been frequently used as photocatalysts for the hydrogen evolution reaction (HER) using sacrificial agents with UV-vis or visible light irradiation. The aim of the present review is to summarize the use of MOFs as solar-driven photocatalysts targeting to overcome the current efficiency limitations in overall water splitting (OWS). Initially, the fundamentals of the photocatalytic OWS under solar irradiation are presented. Then, the different strategies that can be implemented on MOFs to adapt them for solar photocatalysis for OWS are discussed in detail. Later, the most active MOFs reported until now for the solar-driven HER and/or oxygen evolution reaction (OER) are critically commented. These studies are taken as precedents for the discussion of the existing studies on the use of MOFs as photocatalysts for the OWS under visible or sunlight irradiation. The requirements to be met to use MOFs at large scale for the solar-driven OWS are also discussed. The last section of this review provides a summary of the current state of the field and comments on future prospects that could bring MOFs closer to commercial application.

Phosphate removal and recovery by lanthanum-based adsorbents: A review for current advances

Controlling eutrophication and recovering phosphate from water bodies are hot issues in the 21st century. Adsorption is considered to be the best method for phosphate removal because of its high adsorption efficiency and fast removal rate. Among the many adsorbents, lanthanum (La)-based adsorbents have been paid more and more attention due to their strong affinity to phosphorus. This paper reviews research of phosphate adsorption on La-based adsorbents in different La forms, including lanthanum oxide/hydroxide, lanthanum mixed metal oxide/hydroxide, lanthanum carbonate, La³⁺, La-based metal-organic framework (La-MOF) and La-MOF derivatives. The La-based adsorbents can be loaded on many carriers, such as carbon material, clay minerals, porous silica, polymers, industrial wastes, and others. We find that lanthanum oxide/hydroxide and La³⁺ adsorbents are mostly studied, while those in the forms of lanthanum carbonate, La-MOF, and La-MOF derivatives are relatively few. The kinetic process of most phosphate adsorption is pseudo-second-order and the isotherm process is in accordance with the Langmuir model. The cost of La-based and other traditional adsorbents was compared. The adsorption mechanisms are categorized as electrostatic attraction, ligand exchange, Lewis acid-base interaction, ion exchange and surface precipitation. Besides, regeneration methods of La-based adsorbents are mainly acid, alkali, and salt-alkali. In addition, the La-based adsorbents after absorbing phosphate can be directly used as a slow-release fertilizer. This review provides a basis for the research on phosphate adsorption by La-based adsorbents. It should be carried out to further develop La-based materials with high adsorption capacity and good regeneration ability. Meanwhile, studies have been conducted on the reuse of phosphate after desorption, which needs more attention in future research.

Stable Zinc-Based Metal-Organic Framework Photocatalyst for Effective Visible-Light-Driven Hydrogen Production

Herein, a new Zn-MOF material, [Zn(L1)(L2)], 1, was built successfully through a one-pot solvothermal method. The 3D MOF structure was determined by Single X-ray diffraction analysis, IR, and elemental analysis. A series of PXRD tests of 1 after being immersed in different solvents and pH solutions demonstrated the good stability of 1. Interestingly, this material displayed high catalytic activity for the visible-light-driven hydrogen generation under the illumination of white LED in pure water or a mixture of DMF and H₂O without additional photosensitizers and cocatalysts. Besides, the studies also showed that the catalytic activity changed constantly as well as the solvent ratio adjustment of DMF and H₂O from 4:6 to 2:8. Additionally, the catalytic activity reached the best value (743 μmol g^-1 h^-1) when the solvent ratio was 4:6. The heterogeneous nature and recyclability of the MOF catalyst, as well as several factors that affect the catalytic activity, were investigated and described in detail. Moreover, the photocatalytic mechanism for the hydrogen generation of 1 was also proposed based on the fluorescence spectra and UV-vis absorption.

Hollow MoS2-supported MAPbI3 composites for effective photocatalytic hydrogen evolution

A facile and effective electrostatic adsorption method was developed to fabricate H-MoS2/MAPbI3 composites, which improved hydrogen evolution activity and stability.

Upcycling of Hazardous Metals and PET Waste derived Metal-Organic Frameworks: A Review in Recent Progress and Prospects

An intense increase in non-biodegradable plastics and waste metals is an immediate threat to the world and needs to be addressed urgently. There are several strategies deployed to control, eliminate,...

Robust visible-light photocatalytic H2 evolution on 2D RGO/Cd0.15Zn0.85In2S4–Ni2P hierarchitectures

Unique 2D ternary hierarchitectures constructed from reduced graphene oxide nanosheets grown with ultrathin Cd0.15Zn0.85In2S4 nanosheets and Ni2P nanoparticles exhibited an outstanding capability for visible-light photocatalytic H2 production.

Atomically dispersed Pt inside MOFs for highly efficient photocatalytic hydrogen evolution

Pt is carried into the channels of UiO-66 with supercritical carbon dioxide to achieve high activity for hydrogen production by photolysis.

Amorphous NiCoB-coupled MAPbI3 for efficient photocatalytic hydrogen evolution

It was thought that the organic-inorganic hybrid perovskite MAPbI₃ could be used to collect visible light for the photocatalytic hydrogen evolution reaction (HER). However, its ability to generate H₂ is limited. Herein, we synthesized amorphous NiCoB through a redox method and coupled it with MAPbI₃ to form the NiCoB/MAPbI₃ composite photocatalyst by electrostatic self-assembly. 30% NiCoB/MAPbI₃ exhibited the maximum H₂ generation yield of 2625.57 μmol g^-1 h^-1, which was approximately 114 fold that of pristine MAPbI₃ and much better than that of Pt/MAPbI₃. In addition to the excellent photocatalytic HER capability, NiCoB/MAPbI₃ maintained good stability in the 24 h cycling hydrogen evolution experiment. The photoelectric analysis showed that NiCoB as a cocatalyst could realize rapid charge separation. This work can offer a reference for the construction of efficient photocatalysts based on lead halide perovskites.

[Ru(bpy)3]2+@Ce-UiO-66/Mn:Bi2S3 Heterojunction and Its Exceptional Photoelectrochemical Aptasensing Properties for Ofloxacin Detection

A photoelectrochemical (PEC) aptasensor on basis of [Ru(bpy)₃]²⁺@Ce-UiO-66/Mn:Bi₂S₃ composites was constructed for detecting ofloxacin (OFL). First, Ce-UiO-66, prepared by a solvothermal method, had Zr⁴⁺-Zr³⁺ and Ce⁴⁺-Ce³⁺ intervalence cycles to increase the charge separation efficiency. Subsequently, Ce-UiO-66 was further modified by [Ru(bpy)₃]²⁺ and Mn:Bi₂S₃ cosensitization to improve the photoelectric activity. [Ru(bpy)₃]²⁺ not only broadened the range of light absorbed but also reacted with an electron donor to maintain the photoelectric conversion process. Among the [Ru(bpy)₃]²⁺@Ce-UiO-66/Mn:Bi₂S₃ heterojunction, Mn:Bi₂S₃ was a photosensitizer, which maximized the efficiency of the electron-hole separation and significantly improved photocurrent. Then, an aptamer was used as a biorecognition unit for OFL-specific detection. Under the best conditions, the PEC aptasensor realized the sensitive detection of OFL, with a detection range of 0.01-100 nmol/L and a detection limit of 6 pmol/L. In addition, the constructed PEC OFL sensor showed good reproducibility, stability, and specificity.

Molecular Dye-Sensitized Photocatalysis with Metal-Organic Framework and Metal Oxide Colloids for Fuel Production

Colloidal dye-sensitized photocatalysis is a promising route toward efficient solar fuel production by merging properties of catalysis, support, light absorption, and electron mediation in one. Metal-organic frameworks (MOFs) are host materials with modular building principles allowing scaffold property tailoring. Herein, we combine these two fields and compare porous Zr-based MOFs UiO-66-NH2(Zr) and UiO-66(Zr) to monoclinic ZrO2 as model colloid hosts with co-immobilized molecular carbon dioxide reduction photocatalyst fac-ReBr(CO)3(4,4′-dcbpy) (dcbpy = dicarboxy-2,2′-bipyridine) and photosensitizer Ru(bpy)2(5,5′-dcbpy)Cl2 (bpy = 2,2′-bipyridine). These host-guest systems demonstrate selective CO2-to-CO reduction in acetonitrile in presence of an electron donor under visible light irradiation, with turnover numbers (TONs) increasing from ZrO2, to UiO-66, and to UiO-66-NH2 in turn. This is attributed to MOF hosts facilitating electron hopping and enhanced CO2 uptake due to their innate porosity. Both of these phenomena are pronounced for UiO-66-NH2(Zr), yielding TONs of 450 which are 2.5 times higher than under MOF-free homogeneous conditions, highlighting synergistic effects between supramolecular photosystem components in dye-sensitized MOFs.

Efficient Schottky Junction Construction in Metal-Organic Frameworks for Boosting H2 Production Activity

Manipulation of the co-catalyst plays a vital role in charge separation and reactant activation to enhance the activity of metal-organic framework-based photocatalysts. However, clarifying and controlling co-catalyst related charge transfer process and parameters are still challenging. Herein, three parameters are proposed, V transfer (the electron transfer rate from MOF to co-catalyst), D transfer (the electron transfer distance from MOF to co-catalyst), and V consume (the electron consume rate from co-catalyst to the reactant), related to Pt on UiO-66-NH2 in a photocatalytic process. These parameters can be controlled by rational manipulation of the co-catalyst via three steps: i) Compositional design by partial substitution of Pt with Pd to form PtPd alloy, ii) location control by encapsulating the PtPd alloy into UiO-66-NH2 crystals, and iii) facet selection by exposing the encapsulated PtPd alloy (100) facets. As revealed by ultrafast transient absorption spectroscopy and first-principles simulations, the new Schottky junction (PtPd (100)@UiO-66-NH2) with higher V transfer and V consume exhibits enhanced electron-hole separation and H2O activation than the traditional Pt/UiO-66-NH2 junction, thereby leading to a significant enhancement in the photoactivity.

Zeolitic imidazolate frameworks as intrinsic light harvesting and charge separation materials for photocatalysis

Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal organic frameworks that have attracted considerable attention in the past years and have found many applications including heterogeneous catalysis due to their highly ordered porous structure, large surface area, and structural flexibility. However, ZIFs are largely utilized as simple hosts or passive media for dispersing other catalytically active species, resembling the roles of zeolites in catalysis. In contrast, our recent findings show that ZIFs not only have broad absorption across the UV-visible and near IR spectral region but also have an exceptionally long-lived excited charge separated state, suggesting that ZIFs may be used as intrinsic light harvesting and photocatalytic materials rather than as inert hosts. This Perspective will focus on the recent progress on the fundamental studies of the intrinsic light absorption, charge separation, and photocatalytic properties of ZIFs and will discuss the outlook for future development.

A dual-signal self-checking photoelectrochemical immunosensor based on the sole composite of MIL-101(Cr) and CdSe quantum dots for the detection of α-fetoprotein

Designing a photoelectrochemical (PEC) immunosensor that can produce dual photocurrent signals which can refer to each other is a great importance but a big challenge. In this manuscript, a novel dual photocurrent signals immunosensor was constructed for the detection of α-fetoprotein (AFP). Unlike the usual method of using two composite materials to provide cathode and anode photocurrent respectively, this work applies only one compound of MIL-101 (Cr) and CdSe quantum dots (QDs). Thereinto, we found that the photocurrent polarity of MIL-101(Cr) would switch by adjusting applied voltage. And then CdSe QDs was introduced by simple ultrasound mixing to boost the dual photocurrent signals. Furthermore, in the composite of M&C, the electron transfer path between MIL-101(Cr) and CdSe QDs may switch between "Z-type" and "Ⅱ-type" by adjusting voltage. Benefiting by the dual signals, the proposed sensor can not only perform sensitively quantitative detection of α-fetoprotein (AFP), but also can intuitively estimate the accuracy and reliability of the test result by determining whether the corresponding relationship of "cathode photocurrent-analyte concentration-anode photocurrent" is established. The linear ranges of the sensing electrodes as cathode and anode are the same, both from 0.1 to 300 ng mL^-1. The limit of detection (LOD) is 0.082 ng mL^-1 (S/N = 3) when it used as an anode, and the LOD is 0.054 ng mL^-1 (S/N = 3) when it served as cathode. Furthermore, this sensor showed acceptable stability, reproducibility, specificity, and feasibility of detecting AFP in human serum, which has broad development prospects in the early clinical diagnosis.

In-situ development of metal organic frameworks assisted ZnMgAl layered triple hydroxide 2D/2D hybrid as an efficient photocatalyst for organic dye degradation

Metal organic framework (MOF) supported layered triple hydroxide (LTH) 2D/2D hybrid material was prepared by a simple hydrothermal method. The photophysical properties of the prepared samples were investigated through a set of analytical methods such as X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscope, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and mapping. The photocatalytic degradation activity of as prepared 2D/2D MOF-5/LTH hybrid sample was investigated against methylene blue (MB) dye under the UV-visible light irradiation. The degradation efficiency of the MOF-5/LTH hybrid sample was twice a time greater than that of pristine MOF-5, particularly degradation efficiency of the MOF-5, LTH and MOF-5/LTH hybrid samples are 43.3, 57.7 and 98.1% respectively. The Pseudo first order rate and the reusing investigation was further used to study the catalytic activity and stability of the as-synthesized 2D/2D photocatalyst. The observed improvement in the photocatalytic activity of the hybrid samples were owed to enhance visible light absorption, efficient separation and transportation of photoinduced electrons and holes.

Enhanced Visible-Light-Driven Hydrogen Production through MOF/MOF Heterojunctions

A strategy for enhancing the photocatalytic performance of MOF-based systems (MOF: metal-organic framework) is developed through the construction of MOF/MOF heterojunctions. The combination of MIL-167 with MIL-125-NH₂ leads to the formation of MIL-167/MIL-125-NH₂ heterojunctions with improved optoelectronic properties and efficient charge separation. MIL-167/MIL-125-NH₂ outperforms its single components MIL-167 and MIL-125-NH₂, in terms of photocatalytic H₂ production (455 versus 0.8 and 51.2 μmol h^-1 g^-1, respectively), under visible-light irradiation, without the use of any cocatalysts. This is attributed to the appropriate band alignment of these MOFs, the enhanced visible-light absorption, and long charge separation within MIL-167/MIL-125-NH₂. Our findings contribute to the discovery of novel MOF-based photocatalytic systems that can harvest solar energy and exhibit high catalytic activities in the absence of cocatalysts.

Preparation of a hybrids APT@MIL by one-step solvent-thermal method for effectively degrading organics

The attapulgite (APT), a typical nano-rod structured clay was introduced to MIL-101(Fe), a typical eco-friendly iron-based Metal-Organic Framework material (MOF), during the preparation by a one-step solvothermal method, which afforded a novel APT and MOF hybrid (APT@MIL). Based on the characterization of SEM, FT-IR and XRD, it was found that the rod-like crystals of APT determined the size of MIL-101(Fe) while maintaining its regular octahedral crystal form, and the crystal size of MIL-101(Fe) in APT@MIL enlarged 4 times. It was also discovered that the rod-like APT were evenly distributed in MIL-101(Fe) crystals. Using APT@MIL as the photocatalyst, some organic dyes were photodegraded in simulated sunlight. The analysis indicated that APT@MIL has high adsorption and photodegradation activity, the removal rate of methylene blue was up to 99.5%. Finally, the photocatalytic activity of APT@MIL was verified by UV-Vis DRS, photoluminescence spectra. The thermodynamic adsorption, kinetic characteristics adsorption, and removal mechanism of APT@MIL are also discussed. In summary, a novel hybrid material APT@MIL was successfully prepared with good adsorption and photocatalytic performance. It is expected to be used in photocatalytic degradation of dye wastewater.

Photocatalytic hydrogen evolution activity over Pt-assisted metal-organic frameworks dominated by transition metal ions and local coordination environments

Three isostructural pillared-layer frameworks with M-BDC-X layers supported by ditopic HL connectors, [M(HL)(BDC)_0.5X] _n (HL = 4'-(4-hydroxyphenyl)-4,2':6',4″-terpyridine, BDC = terephthalate, M = Cd, X = Cl for (1), M = Cd, X = formate for (2), and M = Co, X = formate for (3)), were solvothermally synthesized, and used as photocatalysts for Pt-assisted visible-light-initiated hydrogen evolution from water splitting. These water-durable frameworks exhibit varied hydrogen production rates of 361.2, 271.3, and 327.5 μmol · g^-1 · h^-1 in 12 h due to their slightly different donor environments of the octahedral Cd^II and Co^II ions. Further experimental and theoretical investigations reveal that the metal ions and the local coordination surroundings have essentially dominated the conduction band minimum and electric resistance of the charge transport, which play highly important roles for the improved catalytic hydrogen evolution ability. These findings demonstrate the electronic effect of the slightly ligand field modifications on the boosting hydrogen generation activity in the noble metal-assisted MOF photocatalytic systems.