Prehydrated Electrons Activated by Continuous Electron Transfer Stemmed from Peracetic Acid Homolysis Mediated by Diamond Surface Defects for Enhanced PFOA Destruction.

Research on the use of peracetic acid (PAA) activated by nonmetal solid catalysts for the removal of dissolved refractory organic compounds has gained attention recently due to its improved efficiency and suitability for advanced water treatment (AWT). Among these catalysts, nanocarbon (NC) stands out as an exceptional example. In the NC-based peroxide AWT studies, the focus on the mechanism involving multimedia coordination on the NC surface (reactive species (RS) path, electron reduction non-RS pathway, and singlet oxygen non-RS path) has been confined to the one-step electron reaction, leaving the mechanisms of multichannel or continuous electron transfer paths unexplored. Moreover, there are very few studies that have identified the nonfree radical pathway initiated by electron transfer within PAA AWT. In this study, the complete decomposition (kobs = 0.1995) and significant defluorination of perfluorooctanoic acid (PFOA, deF% = 72%) through PAA/NC has been confirmed. Through the use of multiple electrochemical monitors and the exploration of current diffusion effects, the process of electron reception and conduction stimulated by PAA activation was examined, leading to the discovery of the dynamic process from the PAA molecule → NC solid surface → target object. The vital role of prehydrated electrons (epre-) before the entry of resolvable electrons into the aqueous phase was also detailed. To the best of our knowledge, this is the first instance of identifying the nonradical mechanism of continuous electron transfer in PAA-based AWT, which deviates from the previously identified mechanisms of singlet oxygen, single-electron, or double-electron single-path transfer. The pathway, along with the strong reducibility of epre- initiated by this pathway, has been proven to be essential in reducing the need for catalysts and chemicals in AWT.

In-Cell Engineering of Protein Crystals into Hybrid Solid Catalysts for Artificial Photosynthesis.

The emergence of protein-based crystalline materials offers promising opportunities in enzyme immobilization. However, the current systems used for encapsulation of protein crystals are limited to either exogenous small molecules or monomeric proteins. In this work, polyhedra crystals were used to simultaneously encapsulate the foreign enzymes FDH and the organic photocatalyst eosin Y. These hybrid protein crystals are prepared easily by cocrystallization within a cell without a requirement for complex purification processes because they spontaneously form 1 µm scale solid particles. After immobilization within protein crystals, the recombinant FDH is recyclable and thermally stable and maintains 94.4% activity compared to the free enzyme. In addition, the incorporation of eosin Y endows the solid catalyst with CO2-formate conversion activity based on a cascade reaction. This work indicates that engineering protein crystals by both in vivo and in vitro strategies will provide robust and environmentally friendly solid catalysts for artificial photosynthesis.

Operando Spectroscopy to Understand Dynamic Structural Changes of Solid Catalysts.

Solid materials like heterogeneous catalysts are highly dynamic and continuously tend to change when exposed to the reaction environment. To understand the catalyst system under true reaction conditions,operando spectroscopy is the key to unravel small changes, which can ultimately lead to a significant difference in catalytic activity and selectivity. This was also the topic of the 7th International Congress on Operando Spectroscopy in Switzerland in 2023. In this article, we discuss various examples to introduce and demonstrate the importance of this area, including examples from emission control for clean air (e.g. CO oxidation), oxidation catalysis in the chemical industry (e.g. oxidation of isobutene), future power-to-X processes (electrocatalysis, CO2 hydrogenation to methanol), and non-oxidative conversion of methane. All of these processes are equally relevant to the chemical industry. Complementary operando techniques such as X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and Raman spectroscopy were utilized to derive the ultimate structure of the catalyst. The variety of conditions requires distinctly different operando cells that can reach a temperature range of 400-1000 °C and pressures up to 40 bar. The best compromise for both the spectroscopy and the catalytic reaction is needed. As an outlook, we highlight emerging methods such as modulation-excitation spectroscopy (MES) or quick-extended X-ray absorption fine structure (QEXAFS) and X-ray photon in/out techniques, which can provide better sensitivity or extend X-ray based operando studies.

Degradation of Perfluorooctanoic Acid with Hydrated Electron by a Heterogeneous Catalytic System.

Hydrated electron (eaq-)-induced reduction protocols have bright prospects for the decomposition of recalcitrant organic pollutants. However, traditional eaq- production involves homogeneous sulfite photolysis, which has a pH-dependent reaction activity and might have potential secondary pollution risks. In this study, a heterogeneous UV/diamond catalytic system was proposed to decompose of a typical persistent organic pollutant, perfluorooctanoic acid (PFOA). In contrast to the rate constant of the advanced reduction process (ARP) of a UV/SO32-, the kobs of PFOA decomposition in the UV/diamond system showed only minor pH dependence, ranging from 0.01823 ± 0.0014 min-1 to 0.02208 ± 0.0013 min-1 (pH 2 to pH 11). As suggested by the electron affinity (EA) and electron configuration of the diamond catalyst, the diamond catalyst yields facile energetic photogenerated electron emission into water without a high energy barrier after photoexcitation, thus inducing eaq- production. The impact of radical scavengers, electron spin resonance (ESR), and transient absorption (TA) measurements verified the formation of eaq- in the UV/diamond system. The investigation of diamond for ejection of energetic photoelectrons into a water matrix represents a new paradigm for ARPs and would facilitate future applications of heterogeneous catalytic processes for efficient recalcitrant pollutant removal by eaq-.

Modifying the Electrocatalytic Selectivity of Oxidation Reactions with Ionic Liquids.

The "solid catalyst with ionic liquid layer" (SCILL) is an extremely successful new concept in heterogeneous catalysis. The idea is to boost the selectivity of a catalyst by its modification with an ionic liquid (IL). Here, we show that it is possible to use the same concept in electrocatalysis for the selective transformation of organic compounds. We scrutinize the electrooxidation of 2,3-butanediol, a reaction which yields two products, singly oxidized acetoin and doubly oxidized diacetyl. When adding the IL (1-ethyl-3-methyl-imidazolium trifluormethanesulfonate, [C2 C1 Im][OTf]), the selectivity for acetoin increases drastically. By in situ spectroscopy, we analyze the underlying mechanism: Specific adsorption of the IL anions suppresses the activation of water for the second oxidation step and, thus, enhances the selectivity for acetoin. Our study demonstrates the great potential of this approach for selective transformation of organic compounds.

Transient Kinetic Selectivity in Nanotubes Growth on Solid Co-W Catalyst.

Solid Co-W catalysts have been shown to yield single-walled carbon nanotubes (CNT) with high selectivity, simplistically attributed to CNT-catalyst symmetry match for certain chiral indices ( n, m). Here, based on large-scale first-principles calculations combined with kinetic Monte Carlo simulations, we show instead that such selectivity arises from a complex kinetics of growth. The solid Co7W6 catalyst strongly favors a restructured, asymmetric CNT edge which entails preferential nucleation of tubes with 2 m < n but much faster growth of chiral tubes with n ⩽ 2 m. We uncover a tendency of interface defects formation that, although rare, drive CNT type change from smaller to larger chiral angles (zigzag to armchair). Being both least prone to defects and fast growing, the (12,6) CNT appears as a transient, kinetics-selected type reaching highest abundance.

Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals.

In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)-(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized.

From waste biomass to solid support: lignosulfonate as a cost-effective and renewable supporting material for catalysis.

Lignosulfonate (LS) is an organic waste generated as a byproduct of the cooking process in sulfite pulping in the manufacture of paper. In this paper, LS was used as an anionic supporting material for immobilizing cationic species, which can then be used as heterogeneous catalysts in some organic transformations. With this strategy, three lignin-supported catalysts were prepared including 1) lignin-SO3 Sc(OTf)2 , 2) lignin-SO3 Cu(OTf), and 3) lignin-IL@NH2 (IL=ionic liquid). These solid materials were then examined in many organic transformations. It was finally found that, compared with its homogeneous counterpart as well as some other solid catalysts that are prepared by using different supports with the same metal or catalytically active species, the lignin-supported catalysts showed better performance in these reactions not only in terms of activity but also with regard to recyclability.

Interparticle Hydrogen Spillover in Enhanced Catalytic Reactions.

Interparticle hydrogen spillover is the phenomenon of H migration over different catalyst particles, which should be a physical mixture of at least two solid catalysts. In this review, we analyze examples of enhanced catalysis based on interparticle (reverse) hydrogen spillover. Simple physical mixtures of powdered catalysts containing metal catalysts of H2 dissociation/recombination and solid catalysts with active sites for substrate activation significantly enhance catalytic reactions. These reactions include aromatic hydrogenation, CO2 methanation, and the deoxydehydration of polyols, aromatization of lower paraffins, and direct coupling of benzene and alkanes. The acceleration effect and proposed reaction pathway of each example involving interparticle (reverse) hydrogen spillover are summarized. Simple reaction systems comprising physical mixtures of at least two powdery solid catalysts should enable unique catalysis in the future with the aid of interparticle (reverse) hydrogen spillover.

Alkyl ammonium hydrogen sulfate immobilized on Fe3O4@SiO2 nanoparticles: a highly efficient catalyst for the multi-component preparation of novel tetrazolo[1,5-a]pyrimidine-6-carboxamide derivatives.

In this, a three-component reaction for the preparation of novel tetrazolo[1,5-a]pyrimidine-6-carboxamide derivatives from N,N'-(sulfonylbis(1,4-phenylene))bis(3-oxobutanamide), aldehydes and 1H-tetrazol-5-amine is reported. The application of Fe3O4@SiO2-(PP)(HSO4)2 (A) as a catalyst afforded the desired products (a1-a18) in high yields in DMF as solvent as well as under solvent-free conditions.

Sulfonic Acid-Grafted Hybrid Porous Polymer Based on Double-Decker Silsesquioxane as Highly Efficient Acidic Heterogeneous Catalysts for the Alcoholysis of Styrene Oxide.

ß-Alkoxyalcohols generated from epoxide ring-opening reactions are significant due to their enormous value as pharmaceutical intermediates and fine chemicals. Using a phenyl-substituted double-decker-type silsesquioxane as the precursor, a hybrid porous material (PCS-DDSQ) was synthesized through a Scholl coupling reaction with an AlCl3 catalyst. Then, novel excellent Brønsted acid-derived silsesquioxane solid catalysts (PCS-DDSQ-SO3H-x) were successfully obtained through an electrophilic aromatic substitution reaction of chlorosulfonic acid on phenyl rings of PCS-DDSQ, fully characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffraction, temperature-programmed desorption, water contact angle, Brunauer-Emmett-Teller model, thermogravimetric analysis, and solid-state 13C and 29Si nuclear magnetic resonance techniques. The catalytic behavior of the PCS-DDSQ-SO3H-x with different SO3H loadings for the methanolysis of styrene oxide was compared and evaluated. The presence of SO3H groups endows them with excellent catalytic abilities, achieving the highest values from PCS-DDSQ-SO3H-1 (the acid site of its catalyst is 1.84 mmol/g) as 99% conversion and 100% selectivity for the methanolysis of styrene oxide in 30 min, which shows superior catalytic properties of low dosage and high efficiency. Furthermore, the PCS-DDSQ-SO3H-1 catalyst can maintain high activity and selectivity after three cycles. This study provides a feasible method for the preparation of Brønsted solid acid catalysts with different acid loadings by introducing the sulfonic group into PCS-DDSQ.

Conversion of N-Acetylglucosamine to 3-Acetamido-5-Acetylfuran over Al-Exchanged Montmorillonite.

3-Acetamido-5-acetylfuran (3A5AF) is a potential platform compound for the production of nitrogen-containing pharmaceuticals and chemicals. 3A5AF can be obtained by dehydration of chitin or its monomer, N-acetylglucosamine (NAG). Here, we examined the use of solid catalysts for the dehydration of NAG to 3A5AF to achieve a more economical process that uses a recyclable catalyst. NAG was dehydrated using various solid catalysts in the presence of NaCl and N,N-dimethyl acetamide as solvent at 433 K. The yield of 3A5AF with the solid catalysts decreased in the following order: Al-exchanged montmorillonite>H-ZSM-5 (SiO2 /Al2 O3 =40)>H-montmorillonite (K-10)>Amberlyst15>H-ZSM-5 (SiO2 /Al2 O3 =300)>TiO2 >γ-Al2 O3 >ZrO2 >SiO2 ⋅ MgO>Na-montmorillonite. The highest yield of 3A5AF (14 %) was obtained with the Al-exchanged montmorillonite. The montmorillonite catalysts were characterized by using inductively coupled plasma optical emission spectroscopy, energy-dispersive X-ray spectroscopy, N2 adsorption, Fourier-transformed infrared spectroscopy, X-ray diffraction, and 27 Al magic-angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR). In addition, a combined catalyst of Al-exchanged montmorillonite and Cl- from synthetic hydrotalcite was found to be an active and recyclable solid catalyst for NAG dehydration to 3A5AF.

One-step electrodeposition of ZnO/graphene composites with enhanced capability for photocatalytic degradation of organic dyes.

Zinc oxide is a popular semiconductor used in catalysts due to its wide bandgap and high exciton binding energy. However, the photocatalytic performance of ZnO was compromised by its insufficient electron-hole separation efficiency and electron transfer rate. Herein, ZnO-reduced graphene oxide (rGO) composite solid catalyst was synthesized by one-step electrodeposition method on FTO substrate using lithium perchlorate (LiClO4) as the supporting electrolyte. Scanning electron microscopy, Raman, Fourier Transform Infrared, and XRD characterizations confirmed the deposition of ZnO and the reduction of graphene oxide Owing to the cooperative effect between rGO and ZnO, the as-prepared ZnO-rGO composites show much enhanced photocatalytic degradation ability compared with pure ZnO nanorods. By optimizing the conditions of electrodeposition of ZnO-rGO composites, the degradation rate of methylene blue can reach 99.1% within 120 min. Thus, the simple preparation and the excellent performance could endow the ZnO-rGO composites with promising application in practical dye-polluted water treatment.

Size-activity threshold of titanium dioxide-supported Cu cluster in CO oxidation.

Development of non-noble metal cluster catalysts, aiming at concurrently high activity and stability, for emission control systems has been challenging because of sintering and overcoating of clusters on the support. In this work, we reported the role of well-dispersed copper nanoclusters supported on TiO2 in CO oxidation under industrially relevant operating conditions. The catalyst containing 0.15 wt% Cu on TiO2 (0.15 CT) exhibited a high dispersion (59.1%), a large specific surface area (381 m2/gCu), a small particle size (1.77 nm), and abundant active sites (75.8% Cu2O). The CO oxidation activity measured by the turnover frequency (TOF) was found to be enhanced from 0.60 × 10-3 to 3.22 × 10-3 molCO·molCu-1·s-1 as the copper loading decreased from 5 to 0.15 wt%. A CO conversion of approximately 60% was still observed in the supported cluster catalyst with a Cu loading of 5 wt% at 240 °C. No deactivation was observed for catalysts with low copper loading (0.15 and 0.30 CT) after 8 h of time-on-stream, which compares favorably with less stable Au cluster-based catalysts reported in the literature. In contrast, catalysts with high copper loading (0.75 and 5 CT) showed deactivation over time, which was ascribed to the increase in copper particle size due to metal cluster agglomeration. This study elucidated the size-activity threshold of TiO2-supported Cu cluster catalysts. It also demonstrated the potential of the supported Cu cluster catalyst at a typical temperature range of diesel engines at light-load. The supported Cu cluster catalyst could be a promising alternative to noble metal cluster catalysts for emission control systems.

Nitro functionalized chromium terephthalate metal-organic framework as multifunctional solid acid for the synthesis of benzimidazoles.

In the present work, nitro functionalized chromium terephthalate [MIL-101(Cr)-NO2] metal- organic framework is prepared and characterized by powder X-ray diffraction (XRD), elemental analysis, infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area. The inherent Lewis acidity of MIL-101(Cr)-NO2 is confirmed by FT-IR spectroscopy using CD3CN as a probe molecule. The performance of MIL-101(Cr)-NO2 as bifunctional catalyst (acid and redox) promoting the synthesis of wide range of benzimidazoles has been examined by catalyzed condensation on acid sites and subsequent oxidative dehydrogenation. The catalytic activity of MIL-101(Cr)-NO2 is found to be superior than analogues catalysts like MIL-101(Cr)-SO3H, MIL-101(Cr)-NH2, UiO-66(Zr), UiO-66(Zr)-NO2, MIL-100(Fe) and Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) under identical reaction conditions. The structural stability of MIL-101(Cr)-NO2 is supported by leaching analysis and reusability tests. MIL-101(Cr)-NO2 solid is used five times without decay in its activity. Comparison of the fresh and five times used MIL-101(Cr)-NO2 solids by powder XRD, SEM and elemental analysis indicate identical crystallinity, morphology and the absence of chromium leaching, respectively.

Production of 5-hydroxymethylfurfural from starch-rich food waste catalyzed by sulfonated biochar.

Sulfonated biochar derived from forestry wood waste was employed for the catalytic conversion of starch-rich food waste (e.g., bread) into 5-hydroxymethylfurfural (HMF). Chemical and physical properties of catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and elemental analysis. The conversion of HMF was investigated via controlling the reaction parameters such as catalyst loading, temperature, and reaction time. Under the optimum reaction conditions the HMF yield of 30.4 Cmol% (i.e., 22 wt% of bread waste) was achieved in the mixture of dimethylsulfoxide (DMSO)/deionized-water (DIW) at 180 °C in 20 min. The effectiveness of sulfonated biochar catalyst was positively correlated to the density of strong/weak Brønsted acidity (SO3H, COOH, and OH groups) and inversely correlated to humins content on the surface. With regeneration process, sulfonated biochar catalyst displayed excellent recyclability for comparable HMF yield from bread waste over five cycles.

Catalytic conversion of corncob and corncob pretreatment hydrolysate to furfural in a biphasic system with addition of sodium chloride.

Catalytic conversion of corncob pretreatment hydrolysate and raw corncob into furfural in a modified biphasic system by SO42-/SnO2- MMT solid catalyst has been developed. The influence of the organic solvent type, organic to water phase ratio, sodium chloride concentration, reaction temperature and time on the furfural production were comparatively evaluated. The results showed that furfural yields of 81.7% and 66.1% were achieved at 190°C for 15mins and 190°C for 20mins, respectively, for corncob pretreatment hydrolysate and raw corncob by this solid catalyst. The solid catalyst used in this study exhibited good stability and high efficiency applied in the modified biphasic system in addition to excellent recyclability. The proposed catalytic system displayed high performance for catalytic conversion of lignocellulosic biomass into important platform chemicals and has great potential in industrial application.

Conversion of lipids from wet microalgae into biodiesel using sulfonated graphene oxide catalysts.

Four solid acid catalysts including graphene oxide (GO), sulfonated graphene oxide (SGO), sulfonated graphene (SG), and sulfonated active carbon (SAC) were used to convert lipids in wet microalgae into biodiesel. The physiochemical properties of the catalysts were characterized with scanning electron microscope, X-ray diffraction, and thermogravimetric analysis. SGO provided the highest conversion efficiency (84.6% of sulfuric acid) of lipids to fatty acid methyl esters (FAME). Whereas SAC converted few lipids into FAME. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that much higher hydrophilic hydroxyl content in SGO catalyst resulted in a considerable higher conversion efficiency of lipids to FAME than that (48.6%) catalyzed by SG, although SO3H groups (0.44mmol/g) in SGO were less than those (1.69mmol/g) in SG. Given its higher SO3H group content than GO (0.38mmol/g), SGO had higher conversion efficiency than GO (73.1%), when they had similar hydrophilic hydroxyl contents.

A review of biochar-based catalysts for chemical synthesis, biofuel production, and pollution control.

This review addresses the use of biochar as a green and versatile catalyst support for emerging high-end applications beyond soil remediation, including chemical synthesis and biodiesel production from biomass, and pollutant degradation in the environment. Their catalytic performances are comparable or even superior to the conventional resin-, silica-, or carbon-based catalysts, owing to the favourable intrinsic features of biochar (various functional groups, intricate network of structures, etc.). Yet, distinctive active sites are needed for different applications. It is highlighted that the active site accessibility for substrates critically determines the performance, which is associated with the biochar physicochemical characteristics (-SO3H site density, pore size distribution, surface area, etc.). They show varying significance depending on the catalytic sites on biochar, which may be controlled via novel pre-/post-synthesis modifications. This review elucidates the links among catalytic performances, physicochemical properties, and pyrolysis/modification-induced features, advising the tailored production of application-oriented biochar-based catalyst in the future.

Porous polymers bearing functional quaternary ammonium salts as efficient solid catalysts for the fixation of CO2 into cyclic carbonates.

A series of porous polymers bearing functional quaternary ammonium salts were solvothermally synthesized through the free radical copolymerization of divinylbenzene (DVB) and functionalized quaternary ammonium salts. The obtained polymers feature highly cross-linked matrices, large surface areas, and abundant halogen anions. These polymers were evaluated as heterogeneous catalysts for the synthesis of cyclic carbonates from epoxides and CO2 in the absence of co-catalysts and solvents. The results revealed that the synergistic effect between the functional hydroxyl groups and the halide anion Br(-) afforded excellent catalytic activity to cyclic carbonates. In addition, the catalyst can be easily recovered and reused for at least five cycles without significant loss in activity.