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CO2valorization relies on the catalytic power of O-vacancies. Yet, these defects are elusive. Operando combination of various spectroscopic techniques sheds light about structure–function relationships to improve catalysis design.

Covalent organic frameworks (COFs), an emerging class of crystalline porous materials, have garnered significant interest due to their low density, tunable chemical and physical properties, porous structure, and high surface area. COFs typically exhibit microporosity, i.e., pores below 2 nm influenced by their specific linkers and binding patterns. In addition, some COFs are reported to exhibit small mesopores, especially when extended linkers are used. In applications such as catalysis, where rapid mass transport is a crucial factor, hierarchical pore structures of catalysts are beneficial. This involves the presence of small micropores to generate a large surface area and additional macropores to facilitate the transport of reactants to catalytic sites and to promote product diffusion. This study describes the application of such a hierarchical porous COF (macro-TpBpy) for photocatalysis. The macro-TpBpy architecture seamlessly integrates intrinsic microporosity with additional macropores, thereby yielding a substantial increase in the surface area. The hierarchical porous material demonstrates a promising performance in photocatalytic hydrogen evolution reaction, exhibiting a rate of 4.88 mmol g–1h–1. Notably, this is a fourfold improvement compared to the COF analogue featuring micropores only. Furthermore, the introduction of macropores proved to be beneficial for the photocatalytic production of hydrogen peroxide (H2O2). Specifically, macro-TpBpy exhibited a production rate of 2716 μmol g–1h–1, in water without sacrificial hole scavengers, whereas pristine TpBpy had a rate of 2134 μmol g–1h–1. This work thus contributes to the further development of COFs in photocatalysis and shows that, in addition to suitable band structure and surface functionality, the pore size and substrate transport influenced by it must also be considered as important factors.

Metal–organic frameworks (MOFs) have garnered substantial attention for their unique properties, such as high porosity and tunable structures, making them versatile for various applications. This paper constructs photoactive titanium–organic frameworks by combining Ti(IV) clusters and a bipyridine linker. The MOF is synthesized in situthrough imine condensation, resulting in NU-2300. Subsequent ex situnickel salt complexation results in NU-2300-Ni, which is then used for light-mediated carbon–heteroatom cross-couplings. The photophysical properties of the metallaphotocatalyst were investigated by UV–vis and EPR analyses, and both the Ti cluster and the bipyridine linker were found to contribute to successful catalysis, making it a tandem catalyst. The heterogeneous material retained its performance through five cycles of thioetherification. This work contributes not only to MOF synthetic strategies but also to expanding MOF applications as recyclable, tandem metallaphotocatalysts.

Multicomponent reactions (MCRs) can be used to introduce different functionalities into highly stable covalent organic frameworks (COFs). In this work, the irreversible three-component Doebner reaction is utilized to synthesize four chemically stable quinoline-4-carboxylic acid DMCR-COFs (DMCR-1–3and DMCR-1NH) equipped with an acid–base bifunctionality. These DMCR-COFs show superior photocatalytic H2O2evolution (one of the most important industrial oxidants) compared to the imine COF analogue (Imine-1). This is achieved with sacrificial oxidants but also in pure water and under an oxygen or air atmosphere. Furthermore, the DMCR-COFs show high photostability, durability, and recyclability. MCR-COFs thus provide a viable materials’ platform for solar to chemical energy conversion.

The metathesis of ethylene with 2-butene to propene is currently applied for large-scale on-purpose production of this building block of the chemical industry. MoOx-based supported catalysts are promising alternatives to the industrially applied WOx-containing systems. The activity of such catalysts depends on the amount of active Mo–carbene (MoCHR) sites formed in situupon reaction of supported MoOxspecies with olefins. Herein, we demonstrate a way to control the ability of such species on the surface of AlSiOxto be transformed into Mo–carbenes by promoting the support with tiny amounts of alkali or alkaline earth metal (Li, Sr, Ca, Mg, Na, K, Ba, Rb, or Cs) oxides. The electrophilic properties of these additives were established to be relevant for in situtransformation of supported MoOxspecies into Mo–carbenes. The additive electronegativity (Pauling scale) affects olefin adsorption and therefore the formation of carbenes.

Isotope labelling, particularly deuteration, is an important tool for the development of new drugs, specifically for identification and quantification of metabolites. For this purpose, many efficient methodologies have been developed that allow for the small-scale synthesis of selectively deuterated compounds. Due to the development of deuterated compounds as active drug ingredients, there is a growing interest in scalable methods for deuteration. The development of methodologies for large-scale deuterium labelling in industrial settings requires technologies that are reliable, robust and scalable. Here we show that a nanostructured iron catalyst, prepared by combining cellulose with abundant iron salts, permits the selective deuteration of (hetero)arenes including anilines, phenols, indoles and other heterocycles, using inexpensive D2O under hydrogen pressure. This methodology represents an easily scalable deuteration (demonstrated by the synthesis of deuterium-containing products on the kilogram scale) and the air- and water-stable catalyst enables efficient labelling in a straightforward manner with high quality control.

Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical1,2. The commercial PDH technologies utilizing Cr-containing (refs. 3,4) or Pt-containing (refs. 5–8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnOxspecies are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnOxspecies. For benchmarking purposes, the developed ZnO–silicalite-1 and an analogue of commercial K–CrOx/Al2O3were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity.

A series of hybrid porous polymers (HPPs) based on polyhedral oligomeric silsesquioxane (POSS) were synthesized, characterized, and successfully used as metal-free heterogeneous photocatalysts for cross-dehydrogenative coupling reactions (CDC), for which the aza-Henry coupling of tetrahydroisoquinolines and nitroalkanes was studied as the model reaction. The reactions run smoothly at room temperature under visible (blue) light irradiation using gaseous oxygen as an oxidant under atmospheric pressure. These novel metal-free heterogeneous photocatalysts can be readily recovered and reused without a significant loss of reactivity. Mechanistic investigations revealed the intermediacy of 1O2, obtained from 3O2sensitization (energy transfer) by the photoexcited catalyst.

Manganese (Mn)-doped ZnS nanocrystals (NCs) have been extensively explored for optical applications with the advantages of low toxicity, large Stokes shifts, and enhanced thermal and environmental stability. Although numerous studies on Mn-doped ZnS dots, rods, and wires have been reported, the literature related to Mn-doped ZnS nanoplatelets (ZnS:Mn NPLs) is scarce. Here, we present the first example of direct doping of Mn2+ions into ZnS NPLs via the nucleation-doping strategy. The resulting ZnS:Mn NPLs exhibit Mn luminescence, indicative for successful doping of the host ZnS NPLs with Mn2+ions. The energy transfer from the ZnS NPLs to the Mn2+ions was observed by employing spectroscopic methods. Furthermore, the impact of the Mn concentration on the optical properties of ZnS:Mn NPLs was systematically investigated. As a result of Mn–Mn interaction, tunable Mn emission and shortened photoluminescence (PL) lifetime decay were observed and rationalized by means of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). Finally, we show that the initially low dopant PL quantum yield (QY) of ZnS:Mn NPLs can be dramatically enhanced by passivating the surface trap states of the samples. The presented synthetic strategy of ZnS:Mn NPLs opens a new way to synthesize further doped systems of two-dimensional (2D) NPLs.

The impact of formaldehyde (HCHO, formed in vehicle exhaust gases by incomplete combustion of fuel) on the performance of a commercial V2O5-WO3/TiO2catalyst in NH3-SCR of NOxunder dry conditions has been analyzed in detail by catalytic tests, in situ FTIR and transient studies using temporal analysis of products (TAP). HCHO reacts preferentially with NH3to a formamide (HCONH2) surface intermediate. This deprives NH3partly from its desired role as a reducing agent in the SCR and diminishes NO conversion and N2selectivity. Between 250 and 400 °C, HCONH2decomposes by dehydration (major pathway) and decarbonylation (minor pathway) to liberate toxic HCN and CO, respectively. HCN was proven to be oxidized by lattice oxygen of the catalyst to CO2and NO, which enters the NH3-SCR reaction.

Photocatalytic ozonation (light/O3/photocatalyst), an independent advanced oxidation process (AOP) proposed in 1996, has demonstrated over the past two decades its robust oxidation capacity and potential for practical wastewater treatment using sunlight and air (source of ozone). However, its development is restricted by two main issues: (i) a lack of breakthrough catalysts working under visible light (42–43% of sunlight in energy) as well as ambiguous property–activity relationships and (ii) unclear fundamental reasons underlying its high yield of hydroxyl radicals (•OH). In this Account, we summarize our substantial contributions to solving these issues, including (i) new-generation graphitic carbon nitride (g-C3N4) catalysts with excellent performance for photocatalytic ozonation under visible light, (ii) mechanisms of charge carrier transfer and reactive oxygen species (ROS) evolution, (iii) property–activity relationships, and (iv) chemical and working stabilities of g-C3N4catalysts. On this basis, the principles/directions for future catalyst design/optimization are discussed, and a new concept of integrating solar photocatalytic ozonation with catalytic ozonation in one plant for continuous treatment of wastewater regardless of sunlight availability is proposed.

A family of six structurally related heteroleptic copper(i) complexes of the form of [Cu(N^N)(P^P)]+bearing a 2,9-dimethyl-1,10-phenanthroline diimine (N^N) ligand and a series of electronically tunable xantphos (P^P) ligands have been synthesized and their optoelectronic properties characterized. The reactivity of these complexes in the copper-photocatalyzed aza-Henry reaction of N-phenyltetrahydroisoquinoline was evaluated, while the related excited state kinetics were comprehensively studied. By subtlety changing the electron-donating properties of the P^P ligands with negligible structural differences, we could tailor the photoredox properties and relate them to the reactivity. Moreover, depending on the exited-state redox potential of the catalysts, the preferred mechanism can shift between reductive quenching, energy transfer and oxidative quenching pathways. A combined study of the structural modulation of copper(i) photocatalysts, optoelectronic properties and photocatalytic reactivity resulted in a clearer understanding of both the rational design of the photocatalyst and the complexity of competing photoinduced electron and energy transfer mechanisms.

Despite the significant progress that has been made in the area of catalyst-dependent chemistry, the exploration of a greener and more environmentally benign catalyst-free reaction remains one of the most important areas in modern chemistry. Herein, we present a vinylboron self-promoted carbonylative coupling with cyclobutanone oxime esters. Various cyclobutanone oxime esters and substituted styrylboronic acids can be transformed into the corresponding enones in moderate to good yields. Detailed EPR investigations and control experiments provide sufficient evidence to show that this reaction goes through a single-electron transfer process.

The operandomethodology is instrumental in catalysis science to assess catalyst structure, performance, dynamics, and kinetics under working conditions. This review analyzes the progress achieved mainly in thermal catalysis to combine different techniques and obtain the interdependency between catalyst structure, function, and reaction media. We analyze various materials of construction, reactor designs, contact types of the catalyst with the reactant, and modes of operation. We also highlight recent studies on combining these techniques and augmenting the obtained data by focusing on instrumentation and experimental design. We review the different reactors/cells used for different applications to understand the type of information received, limitations, and the design principles of these instruments. We provide our viewpoints on integrating spectroscopy, catalysis science, and reaction engineering; these advanced operandotechniques can offer a more comprehensive image of catalysts at work.

Supported V2O5/Ce0.5Ti0.5−xMnxO2−δ(x= 0, 0.01, 0.05, 0.1, and 0.2) catalysts and bare supports were investigated in the selective catalytic reduction (SCR) of NO by NH3between 100 and 300 °C. Incorporation of Mn into Ce0.5Ti0.5O2increased the NO removal efficiency, reaching both NO and NH3conversions above 85% between 175 to 300 °C at remarkably high N2selectivities of ≥95%. Moreover, Mn-modified supports were also much more stable against deactivation in the presence of water. Deposition of vanadia on the Ce0.5Ti0.5−xMnxO2−δsupports enhanced the N2selectivity, reaching ≥98% in the whole temperature range for Mn percentages of ≤0.1. Characterization results revealed that incorporation of Mn leads to supports with higher lattice disorder and smaller crystallite size and enhances the oxygen mobility and the reducibility of the supports. OperandoEPR studies show that the synergistic effect of VOxand MnOxsurface species in moieties containing Mn3+/Mn2+and VO3+/VO2+in close vicinity contributes to the prevention of undesired NH3oxidation, thus improving the N2selectivity of these catalysts.

Selective aerobic oxidation of benzyl alcohol to benzaldehyde by a (bpy)CuI(IM)/TEMPO catalyst (IM represents differently substituted imidazoles) has been studied by simultaneous operando electron paramagnetic resonance/UV–vis/attentuated total reflectance infrared spectroscopy in combination with cyclic voltammetry to explore the particular role of imidazole in terms of ligand and/or base as well as of its substitution pattern on the catalytic performance. For molar ratios of IM/Cu ≥ 2, a (bpy)CuI/II(IM)a(IM)bcomplex is formed, in which the Cu–N distances and/or angles for the two IM ligands a and b are different. The coordination of a second IM molecule boosts the oxidation of CuIto CuIIand, thus, helps to activate O2by electron transfer from CuIto O2. The rates of CuIoxidation and CuIIreduction and, thus, the rates of benzaldehyde formation depend on R of the R–N moiety in the IM ligand. Oxidation is fastest for R = H and alkyl, while reduction is slowest for R = H. The CuI/CuIIinterplay leads to decreasing total benzaldehyde formation rates in the order R (I+ effect) > R (conjugated system) > R = H.

In recent times, a self-complementary balanced characteristic feature with the combination of both covalent bonds (structural stability) and open metal sites (single-site catalysis) introduced an advanced emerging functional nanoarchitecture termed metalated porous organic polymers (M-POPs). However, the development of M-POPs in view of the current interest in catalysis has been realized still in its infancy and remains a challenge for the years to come. In this work, we built benzothiazole-linked Fe-metalated porous organic polymer (Fc-Bz-POP) using ferrocene dicarboxaldehyde (FDC), 1,3,5-tris(4-aminophenyl) benzene (APB), and elemental sulfur (S8) via a template-free, multicomponent, cost-effective one-pot synthetic approach. This Fc-Bz-POPis endowed with unique features including an extended network unit, isolated active sites, and catalytic pocket with a possible local structure, in which convergent binding sites are positioned in such a way that substrate molecules can be held in close proximity. Prospective catalytic application of this Fc-Bz-POPhas been explored in executing catalytic allylic “C–H” bond functionalization of cyclohexene (CHX) in water at room temperature. Catalytic screening results identified that a superior performance with a CHXconversion of 95% and a 2-cyclohexene-1-ol selectivity (COL) of 80.8% at 4 h and 25 °C temperature has been achieved over Fc-Bz-POP, thereby addressing previous shortcomings of the other conventional catalytic systems. Comprehensive characterization understanding with the aid of synchrotron-based extended X-ray absorption fine structure (EXAFS) analysis manifested that the Fe atom with an oxidation state of +2 in our Fc-Bz-POPcatalytic system encompasses a sandwich structural environment with the two symmetrical eclipsed cyclopentadienyl (Cp) rings, featuring nearest-neighbor (NN) Fe–C (≈2.05 Å) intramolecular bonds, as validated by the Fe L3-edge EXAFS fitting result. Furthermore, in situ attenuated total reflection-infrared spectroscopy (ATR-IR) analysis data for liquid-phase oxidation of cyclohexene allow for the formulation of a molecular-level reaction mechanistic pathway with the involvement of specific reaction intermediates, which is initiated by the radical functionalization of the allyl hydrogen. A deep insight investigation from density functional theory (DFT) calculations unambiguously revealed that the dominant pathway from cyclohexene to 2-cyclohexene-1-ol is initiated by an allyl-H functionalization step accompanied by the formation of 2-cyclohexene-1-hydroperoxide species as the key reaction intermediate. Electronic properties obtained from DFT simulations via the charge density difference plot, Bader charge, and density of state (DOS) demonstrate the importance of the organic polymer frame structure in altering the electronic properties of the Fe site in Fc-Bz-POP, resulting in its high activity. Our contribution has great implications for the precise design of metalated porous organic polymer-based robust catalysts, which will open a new avenue to get a clear image of surface catalysis.

The graphic abstract showcases three stages: laboratory-level research to enhance adsorption, application-level modeling and optimization, and technology coupling in pilot-scale and industrial settings.

Caught by the cage: New vanadium phosphonate cages with a fluoride template inside and charge‐compensating transition‐metal cations outside were prepared in a simple way. The charge and ligand sphere of the cation govern its interaction with the cage and can be used to modify the magnetic and redox properties of the cage, which also depend on the anionic template (see figure).

Herein, we report a photomediated hydro- and deuterodecarboxylation of different primary, secondary, and tertiary carboxylic acids catalyzed by an organic pyrimidopteridine photoredox catalyst. The reaction was optimized by a statistical design of experiment (DoE). Under optimized reaction conditions, the conversion of commercially available nonsteroidal anti-inflammatory drugs (NSAIDs) in tablet form and on gram scale was realized. The scope of the application comprises primary, secondary, and tertiary aliphatic biologically active carboxylic acids. A deuterium incorporation of up to 95% by using D2O as inexpensive deuterium source was achieved. A sensitivity assessment as well as experiments aiding the elucidation of the reaction mechanism are discussed.

Mn2+-doped semiconductor nanocrystals with tuned location and concentration of Mn2+ions can yield diverse coupling regimes, which can highly influence their optical properties such as emission wavelength and photoluminescence (PL) lifetime. However, investigation on the relationship between the Mn2+concentration and the optical properties is still challenging because of the complex interactions of Mn2+ions and the host and between the Mn2+ions. Here, atomically flat ZnS nanoplatelets (NPLs) with uniform thickness were chosen as matrixes for Mn2+doping. Using time-resolved (TR) PL spectroscopy and density functional theory (DFT) calculations, a connection between coupling and PL kinetics of Mn2+ions was established. Moreover, it is found that the Mn2+ions residing on the surface of a nanostructure produce emissive states and interfere with the change of properties by Mn2+–Mn2+coupling. In a configuration with suppressed surface contribution to the optical response, we show the underlying physical reasons for double and triple exponential decay by DFT methods. We believe that the presented doping strategy and simulation methodology of the Mn2+-doped ZnS (ZnS:Mn) system is a universal platform to study dopant location- and concentration-dependent properties also in other semiconductors.

The simultaneous control of the defect species and surface properties of semiconducting materials is a crucial aspect of improving photocatalytic performance, yet it remains challenging. Here, we synthesized Mg–Zr-codoped single-crystalline Ta3N5(Ta3N5:Mg+Zr) nanoparticles by a brief NH3nitridation process, exhibiting photocatalytic water reduction activity 45 times greater than that of pristine Ta3N5under visible light. A coherent picture of the relations between the defect species (comprising reduced Ta, nitrogen vacancies and oxygen impurities), surface properties (associated with dispersion of the Pt cocatalyst), charge carrier dynamics, and photocatalytic activities was drawn. The tuning of defects and simultaneous optimization of surface properties resulting from the codoping evidently resulted in the generation of high concentrations of long-lived electrons in this material as well as the efficient migration of these electrons to evenly distributed surface Pt sites. These effects greatly enhanced the photocatalytic activity. This work highlights the importance and feasibility of improving multiple properties of a catalytic material via a one-step strategy.