Metal doping in cerium metal-organic frameworks for visible-response water splitting photocatalysts

Delocalized Orbitals over Metal Clusters and Organic Linkers Enable Boosted Charge Transfer in Metal-Organic Framework for Overall CO2 Photoreduction

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi-electron transfer process. Herein, taking metal-organic framework (MOF, PFC-98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC-6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge-separated (ICS) state, prolonging the excited state lifetime and further inhibiting the electron-hole recombination. The presence of ICS state prolongs the excited state lifetime and further inhibits the electron-hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi-electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

Optimization of cerium-based metal-organic framework synthesis for maximal sonophotocatalytic tetracycline degradation

Wastewater treatment is inevitably required to alleviate the pollution of water resources by various contaminants such as antibiotics. MOFs are novel materials with photocatalytic activities. In this study, sonophotocatalytic degradation of tetracycline (TC) by the Cerium-based MOF (Ce-MOF) is optimized by modification of its synthesis route. Ce-MOF synthesis by room temperature (RT), hydrothermal (HT), and sonochemical synthesis (SC) are studied. TC degradation experiments revealed the superiority of SC synthesis. The interplay of main synthesis parameters, namely, initial ligand concentration, ultrasound (US) power and time on sonophotocatalytic activity of Ce-MOF, were investigated by response surface methodology model (RSM) utilizing the central composite experimental design (CCD). The optimum SC synthesis conditions are an initial ligand concentration of 8.4 mmol/L, a sonication power of 50 amplitude, and a US time of 60 min. The optimally synthesized Ce-MOF was characterized by infrared spectroscopy, FTIR, XRD, FE-SEM, TEM, zeta potential analysis, diffuse reflectance spectroscopy, particle size analysis, Mott-Schottky analysis, photocurrent analysis, electrochemical impedance spectra, and photoluminescence spectroscopy. The findings indicate that the removal efficiency of TC can reach up to 81.75% within 120 min in an aqueous solution containing an initial TC concentration of 120 ppm and 1 g/L Ce-MOF at pH of 7. Mineralization efficiency of the process is 71% according to COD measurements. The Ce-MOF catalyst retained its chemical stability and remained active upon TC degradation which makes it a promising candidate for wastewater treatment.

CoNiFe alloy nanoparticles encapsulated into nitrogen-doped carbon nanotubes toward superior electrocatalytic overall water splitting in alkaline freshwater/seawater under large-current density

Developing bifunctional catalysts for overall water splitting with high activity and durability at high current density remains a challenge. In an attempt to overcome this bottleneck, in this work, unique CoNiFe-layered double hydroxide nanoflowers are in situ grown on nickel-iron (NiFe) foam through a corrosive approach and following a chemical vapor deposition process to generate nitrogen-doped carbon nanotubes at the presence of melamine (CoNiFe@NCNTs). The coupling effects between various metal species act a key role in accelerating the reaction kinetics. Moreover, the in situ formed NCNTs also favor promoting electrocatalytic activity and stability. For oxygen evolution reaction it requires low overpotentials of 330 and 341 mV in 1M KOH and 1M KOH + seawater to drive 500 mA cm-2. Moreover, water electrolysis can be operated with CoNiFe@NCNTs as both anode and cathode with small voltages of 1.95 and 1.93 V to achieve 500 mA cm-2 in 1M KOH and 1M KOH + seawater, respectively.

Substituted Ti(IV) in Ce-UiO-66-NH2 Metal-Organic Frameworks Increases H2 and O2 Evolution under Visible Light

Metal-organic frameworks (MOFs) as photocatalysts have received increasing attention. In this work, a dual metal-substituted UiO-66-NH₂ (Ti/Ce-MOF) containing different Ti/Ce mole ratios (x = 0-2.46) has been prepared via post-synthetic exchange between Ce-UiO-66 and TiCl₄, followed by amination. The solid had a high surface area (828-937 m²/g) and a large pore volume (0.451-0.507 m³/g). Under visible light, Ti/Ce-MOF showed x-dependent activity for H₂O reduction and oxidation on a film electrode, respectively. However, such a change for H₂ evolution in a Na₂S/Na₂SO₃ aqueous solution was observed only after CdS loading. In combination with the photoluminescence and band parameters, we propose that the photoactivity of Ti/Ce-MOF for redox reaction is determined by its ability for electron transfer. Furthermore, there is an interfacial electron transfer from Ti/Ce-MOF to CdS and a hole transfer from CdS to Ti/Ce-MOF, respectively, significantly improving the efficiency of charge separation for redox reactions. This work offers a new insight that Ti substitution benefits the performance of Ce-based MOF.

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.

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.

Bioinspired Metalation of the Metal-Organic Framework MIL-125-NH2 for Photocatalytic NADH Regeneration and Gas-Liquid-Solid Three-Phase Enzymatic CO2 Reduction

Coenzyme NADH regeneration is crucial for sustained photoenzymatic catalysis of CO₂ reduction. However, light-driven NADH regeneration still suffers from the low regeneration efficiency and requires the use of a homogeneous Rh complex. Herein, a Rh complex-based electron transfer unit was chemically attached onto the linker of the MIL-125-NH₂ . The coupling between the light-harvesting iminopyridine unit and electron-transferring Rh-complex facilitated the photo-induced electron transfer for the NADH regeneration with the yield of 66.4 % in 60 mins for 5 cycles. The formate dehydrogenase was further deposited onto the hydrophobic layer of the membrane by a reverse filtering technique, which forms the gas-liquid-solid reaction interface around the enzyme site. It gave an enhanced formic acid yield of 9.5 mM in 24 hours coupled with the in situ regenerated NADH. The work could shed light on the construction of integrated inorganic-enzyme hybrid systems for artificial photosynthesis.

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.

A Novel Cerium(IV)-Based Metal-Organic Framework for CO2 Chemical Fixation and Photocatalytic Overall Water Splitting

Cerium (IV)-based metal-organic frameworks (MOFs) are highly desirable due to their unique potential in fields such as redox catalysis and photocatalysis. However, due to the high reduction potential of Ce^IV species in solution, it is still a great challenge to synthesize Ce^IV -MOFs with novel structures, which are extremely dominated by the hexanuclear Ce-O cluster inorganic building units (IBUs). Herein, a Ce-O IBU chain containing Ce^IV -MOF, CSUST-3 (CSUST: Changsha University of Science and Technology), was successfully prepared using the kinetic stabilization study of UiO-66(Ce)-NDC (H₂ NDC=2,6-naphthalenedicarboxylic acid). Furthermore, owing to the superior redox activity, Lewis acidity and semiconductor-like behavior owing to Ce⁴⁺ , activated CSUST-3 was demonstrated to be an excellent catalyst for CO₂ chemical fixation. One-pot synthesis of styrene carbonate from styrene and CO₂ was achieved under mild conditions (1 atm CO₂ , 80 °C, and solvent free). Moreover, activated CSUST-3 was shown to be a remarkable co-catalyst-free photocatalyst for overall water splitting (OWS), rendering 59 μmol g^-1  h^-1 of H₂ and 22 μmol g^-1  h^-1 of O₂ under simulated sunlight irradiation (Na₂ S-Na₂ SO₃ as sacrificial agent).

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

A defining characteristic of nearly all catalytically functional MOFs is uniform, molecular-scale porosity. MOF pores, linkers and nodes that define them, help regulate reactant and product transport, catalyst siting, catalyst accessibility, catalyst stability, catalyst activity, co-catalyst proximity, composition of the chemical environment at and beyond the catalytic active site, chemical intermediate and transition-state conformations, thermodynamic affinity of molecular guests for MOF interior sites, framework charge and density of charge-compensating ions, pore hydrophobicity/hydrophilicity, pore and channel rigidity vs. flexibility, and other features and properties. Collectively and individually, these properties help define overall catalyst functional behaviour. This review focuses on how porous, catalyst-containing MOFs capitalize on molecular-scale confinement, containment, isolation, environment modulation, energy delivery, and mobility to accomplish desired chemical transformations with potentially superior selectivity or other efficacy, especially in comparison to catalysts in homogeneous solution environments.

Metal-Organic Frameworks: Molecules or Semiconductors in Photocatalysis?

In the realm of solids, metal-organic frameworks (MOFs) offer unique possibilities for the rational engineering of tailored physical properties. These derive from the modular, molecular make-up of MOFs, which allows for the selection and modification of the organic and inorganic building units that construct them. The adaptable properties make MOFs interesting materials for photocatalysis, an area of increasing significance. But the molecular and porous nature of MOFs leaves the field, in some areas, juxtapositioned between semiconductor physics and homogeneous photocatalysis. While descriptors from both fields are applied in tandem, the gap between theory and experiment has widened in some areas, and arguably needs fixing. Here we review where MOFs have been shown to be similar to conventional semiconductors in photocatalysis, and where they have been shown to be more like infinite molecules in solution. We do this from the perspective of band theory, which in the context of photocatalysis, covers both the molecular and nonmolecular principles of relevance.

Optimal Pore Chemistry in an Ultramicroporous Metal-Organic Framework for Benchmark Inverse CO2 /C2 H2 Separation

Isolation of CO₂ from acetylene (C₂ H₂ ) via CO₂ -selective sorbents is an energy-efficient technology for C₂ H₂ purification, but a strategic challenge due to their similar physicochemical properties. There is still no specific methodology for constructing sorbents that preferentially trap CO₂ over C₂ H₂ . We report an effective strategy to construct optimal pore chemistry in a Ce^IV -based ultramicroporous metal-organic framework Ce^IV -MIL-140-4F, based on charge-transfer effects, for efficient inverse CO₂ /C₂ H₂ separation. The ligand-to-metal cluster charge transfer is facilitated by Ce^IV with low-lying unoccupied 4f orbitals and electron-withdrawing F atoms functionalized tetrafluoroterephthalate, affording a perfect pore environment to match CO₂ . The exceptional CO₂ uptake (151.7 cm³  cm^-3 ) along with remarkable separation selectivities (above 40) set a new benchmark for inverse CO₂ /C₂ H₂ separation, which is verified via simulated and experimental breakthrough experiments. The unique CO₂ recognition mechanism is further unveiled by in situ powder X-ray diffraction experiments, Fourier-transform infrared spectroscopy measurements, and molecular calculations.

Rare-Earth-Based Metal-Organic Frameworks as Multifunctional Platforms for Catalytic Conversion

The development of catalytic conversion is very important for human society. In the catalytic process, metal-organic frameworks (MOFs) can be utilized to obtain effective catalysts for their porous structures and adjustable properties. In addition, the introduction of rare-earth (RE) elements with unique properties for catalysts can realize good catalytic performances. Thus, the RE-MOF related catalysts for catalytic conversion are summarized. Due to the cooperation of RE elements and porous MOF structures, the RE-based MOFs can be used as promising catalysts or precursors/supports for other catalysts in the areas of energy conversion, environmental governance, and organic synthesis. These aggregated studies highlight the RE-MOFs as promising candidates for catalytic conversion.

Spin-Orbit Coupling Changes the Identity of the Hyper-Open-Shell Ground State of Ce+, and the Bond Dissociation Energy of CeH+ Proves to Be Challenging for Theory

Cerium (Ce) plays important roles in catalysis. Its position in the sixth period of the periodic table leads to spin-orbit coupling (SOC) and other open-shell effects that make the quantum mechanical calculation of cerium compounds challenging. In this work, we investigated the low-lying spin states of Ce⁺ and the bond energy of CeH⁺, both by multiconfigurational methods, in particular, SA-CASSCF, MC-PDFT, CASPT2, XMS-PDFT, and XMS-CASPT2, and by single-configurational methods, namely, Hartree-Fock theory and unrestricted Kohn-Sham density functional theory with 34 choices of the exchange-correlation functional. We found that only CASPT2, XMS-CASPT2, and SA-CASSCF (among the five multiconfigurational methods) and GAM, HCTH, SOGGA11, and OreLYP (among the 35 single-configuration methods) successfully predict that the SOC-free ground spin state of Ce⁺ is a doublet state, and CASPT2 and GAM give the most accurate multireference and single-reference calculations, respectively, of the excitation energy of the first SOC-free excited state for Ce⁺. We calculated that the ground doublet state of Ce⁺ is an intra-atomic hyper-open-shell state. We calculated the spin-orbit energy (E^SO) of Ce⁺ by the five multiconfigurational methods and found that E^SO calculated by CASPT2 is the closest to the experimental value. Taking advantage of the availability of an experimental D₀ for CeH⁺ as a way to provide a unique test of theory, we showed that all the multiconfigurational methods overestimate D₀ by at least 246 meV (5.7 kcal/mol), and only three functionals, namely, SOGGA, MN15, and GAM, have an error of D₀ that is less than 200 meV (5 kcal/mol).

Electronic Structure Modeling of Metal-Organic Frameworks

Owing to their molecular building blocks, yet highly crystalline nature, metal-organic frameworks (MOFs) sit at the interface between molecule and material. Their diverse structures and compositions enable them to be useful materials as catalysts in heterogeneous reactions, electrical conductors in energy storage and transfer applications, chromophores in photoenabled chemical transformations, and beyond. In all cases, density functional theory (DFT) and higher-level methods for electronic structure determination provide valuable quantitative information about the electronic properties that underpin the functions of these frameworks. However, there are only two general modeling approaches in conventional electronic structure software packages: those that treat materials as extended, periodic solids, and those that treat materials as discrete molecules. Each approach has features and benefits; both have been widely employed to understand the emergent chemistry that arises from the formation of the metal-organic interface. This Review canvases these approaches to date, with emphasis placed on the application of electronic structure theory to explore reactivity and electron transfer using periodic, molecular, and embedded models. This includes (i) computational chemistry considerations such as how functional, k-grid, and other model variables are selected to enable insights into MOF properties, (ii) extended solid models that treat MOFs as materials rather than molecules, (iii) the mechanics of cluster extraction and subsequent chemistry enabled by these molecular models, (iv) catalytic studies using both solids and clusters thereof, and (v) embedded, mixed-method approaches, which simulate a fraction of the material using one level of theory and the remainder of the material using another dissimilar theoretical implementation.

Boosting Interfacial Charge-Transfer Kinetics for Efficient Overall CO2 Photoreduction via Rational Design of Coordination Spheres on Metal-Organic Frameworks

The recombination of electron-hole pairs severely detracts from the efficiency of photocatalysts. This issue could be addressed in metal-organic frameworks (MOFs) through optimization of the charge-transfer kinetics via rational design of structures at atomic level. Herein, a pyrazolyl porphyrinic Ni-MOF (PCN-601), integrating light harvesters, active catalytic sites, and high surface areas, has been demonstrated as a superior and durable photocatalyst for visible-light-driven overall CO₂ reduction with H₂O vapor at room temperature. Kinetic studies reveal that the robust coordination spheres of pyrazolyl groups and Ni-oxo clusters endow PCN-601 with proper energy band alignment and ultrafast ligand-to-node electron transfer. Consequently, the CO₂-to-CH₄ production rate of PCN-601 far exceeds those of the analogous MOFs based on carboxylate porphyrin and the classic Pt/CdS photocatalyst by more than 3- and 20-fold, respectively. The reaction avoids the use of hole scavengers and proceeds in a gaseous phase which can take full advantage of the high gas uptake of MOFs. This work demonstrates that the rational design of coordination spheres in MOF structures not only reconciles the contradiction between reactivity and stability but also greatly promotes the interfacial charge transfer to achieve optimized kinetics, providing guidance for the design of highly efficient MOF photocatalysts.

Band Alignment as the Method for Modifying Electronic Structure of Metal-Organic Frameworks

Electronic-level ordering in metal-organic frameworks (MOFs) is a route to modulate their electronic properties such as optical absorption, band alignment, work function, charge separation, charge carrier lifetimes, and ground- or excited-state conductivity. A systematic application of this approach requires the knowledge on how a MOF chemical composition affects its electronic structure. In this work, the fundamental principles for selecting MOF components to achieve targeted level alignment are considered. Correlations between the electronic parameters of building blocks and MOF band structure are analyzed. The factors affecting the energy position of constituents are discussed. In particular, the impact of the chemical composition of ligands, including the structure of its scaffold and side groups, on their energy positions in MOFs is addressed. Besides, the effect of the choice of reference potential and surface termination on the band alignment is investigated. The performance of several density functionals in the computation of absolute band positions is assessed. Finally, general principles for the modification of the MOF electronic structure are formulated and the routes to achieve an appropriate band alignment with carrier-transporting materials, co-catalysts, and redox reaction potentials are suggested.

The chemistry of Ce-based metal-organic frameworks

Metal-organic frameworks (MOFs) have gained widespread attention due to their modular construction that allows the tuning of their properties. Within this vast class of compounds, metal carboxylates containing tri- and tetravalent metal ions have been in the focus of many studies due to their often high thermal and chemical stabilities. Cerium has a rich chemistry, which depends strongly on its oxidation state. Ce(iii) exhibits properties typically observed for rare earth elements, while Ce(iv) is mostly known for its oxidation behaviour. In MOF chemistry this is reflected in their unique optical and catalytic properties. The synthetic parameters for Ce(iii)- and Ce(iv)-MOFs also differ substantially and conditions must be chosen to prevent reduction of Ce(iv) for the formation of the latter. Ce(iii)-MOFs are usually reported in comprehensive studies together with those constructed with other RE elements and normally they are isostructural. They exhibit a greater structural diversity, which is reflected in the larger variety of inorganic building units. In contrast, the synthesis conditions of Ce(iv)-MOFs were only recently (2015) established. These lead selectively to hexanuclear Ce-O clusters that are well-known for Zr-MOFs and therefore very similar structural and isoreticluar chemistry is found. Hence Ce(iv)-MOFs exhibit often high porosity, while only a few porous Ce(iii)-MOFs have been described. Some of these show structural flexibility which makes them interesting for separation processes. For Ce(iv)-MOFs the redox properties are most relevant. Thus, they are intensively discussed for catalytic, photocatalytic and sensing applications. In this perspective, the synthesis, structural chemistry and properties of Ce-MOFs are summarized.

Multilink F* Method for Combined Quantum Mechanical and Molecular Mechanical Calculations of Complex Systems

Combined quantum mechanical and molecular mechanical (QM/MM) studies on catalysis in metal-organic frameworks (MOFs) are relatively undeveloped in contrast to the wide use of QM/MM for enzyme catalysis. One reason is that the currently available methods for treating QM-MM boundaries are not fully compatible with the combination of features in MOFs, namely, their high connectivity, their polar bonds (e.g., metal-oxygen bonds), and their potential boundary atoms with high partial atomic charges. The treatment of polar bonds can be improved by using tuned link atoms, but both the widely used H link atom method and the F* link atom method provide limited options in placing the QM-MM boundary in MOFs and other covalently bonded solids, which seriously reduces the efficiency of QM/MM calculations. Here, we propose a generalized version of the F* link atom method with greater flexibility for the placement of the QM-MM boundary in MOFs and with a practical scheme for tuning. The new method, called the multilink F* method, allows a large part of an inorganic node of a MOF to be partitioned into the MM subsystem to increase the efficiency. Our validation calculations on dimerization of ethylene to 1-butene by a nickel catalyst supported on a MOF show that the overall performance of QM/MM calculations with the multilink F* method is excellent for energies, geometries, and partial atomic charges.

Special Topic on Interfacial Electrochemistry and Photo(electro)catalysis

Interfacial electrochemistry and photo(electro)catalysis are key processes that convert the energy of photons or electrons to chemical bonds in many energy conversion and storage technologies. Achieving a molecular level understanding of the fundamental interfacial structure, energetics, dynamics, and reaction mechanisms that govern these processes represents a broad frontier for chemical physics and physical chemistry. This Special Topic contains a collection of articles that range from the development of new experimental and computational techniques to the novel application of those techniques for mechanistic studies, as the principal investigators seek a fundamental molecular understanding of both electrode/electrolyte interfaces and the relevant electrocatalytic, photocatalytic, and photoelectrochemical reactions taking place thereabout. Altogether, this collection of articles captures the current state of this very active, frontier research field and highlights the current and remaining key scientific challenges and opportunities.

Mixed-metal metal–organic frameworks

Mixed-metal MOFs contain at least 2 different metal ions presenting promising potential in heterogeneous catalysis, gas sorption/separation, luminescence and sensing.

Cerium-based UiO-66 metal–organic frameworks explored as efficient redox catalysts: titanium incorporation and generation of abundant oxygen vacancies

For the first time, UiO-66(Ce) was endowed with greatly improved redox photocatalytic activity via Ti incorporation, based on the formation of oxygen vacancies.