Immediate hydroxylation of arenes to phenols via V-containing all-silica ZSM-22 zeolite triggered non-radical mechanism

Anchoring Cu sites in a hierarchical single-crystalline ZSM-5 zeolite for enhanced diffusion and benzene oxidation

Phenol is an important intermediate for high-value chemicals. Current phenol production via the three-step cumene process leads to significant energy waste and environmental problems. The conversion of benzene to phenol under mild conditions can be achieved by oxidation with Cu-based zeolites. However, conventional microporous zeolites suffer from severe diffusion limitations, especially when bulky molecules, such as benzene, are involved. In this work, we used a hierarchically macro-meso-microporous ZSM-5 single crystal (Hier-ZSM-5) as a substrate for Cu species (Cu@Hier-ZSM-5). The irregular morphology of the opal-like Hier-ZSM-5 exhibited abundant surface Si-OH groups and provided a platform for stabilizing Cu2+ sites. Meanwhile, hierarchical porosity significantly improved the diffusion ability of bulky molecules. As a result, excellent selective oxidation performance of benzene was obtained with Cu@Hier-ZSM-5, achieving a conversion of 77% and a phenol selectivity of 73%, which were 1.5 times and 2 times higher than those obtained with a catalyst based on microporous ZSM-5, respectively. CuOOH species were identified as an important intermediate in benzene oxidation. This hierarchical zeolite system, with a synergistic effect of site anchoring and molecular diffusion, provides an excellent platform for catalyst design.

Highly Selective Oxidation of Benzene to Phenol Mediated by KHCO3 in the Bimetallic Mo-Cu/NC-H2O2 System

Although selective oxidation of benzene to phenol (SOBP) by H2O2 is an important chemical process, overoxidation of benzene by the produced nonselective •OH during the activation of H2O2 inevitably reduces the oxidation selectivity. We, therefore, attempt to mediate the oxidation selectively by using electrophilic KHCO3 in the oxidation system. In this study, Mo-Cu/NC has been successfully synthesized via ball-milling bimetallic Mo-Cu and N-doped carbon, which exhibits high reactivity in SOBP by H2O2 and KHCO3 with a desirable phenol yield of 25.1% and selectivity of 100%. A series of characterizations and DFT calculations reveal that the reaction between H2O2 and KHCO3 produces HCO4-, which is then moderately activated on Mo1Cu2/NC via the nonradical pathway with the formation of Mo-(η2-O2) peroxo. Meanwhile, Ov at Mo1Cu2/NC facilitates the adsorption of benzene, which is then selectively oxidized by Mo-(η2-O2) peroxo to phenol via the oxygen atom transfer pathway. This study provides new insights on the importance of Mo-(η2-O2) peroxo mediated by H2O2-KHCO3 in selective oxidation of aromatic C-H bond via the nonradical pathway.

Yb-Doped CuY modulates Cu electronic structures for efficient oxidation of anisole to guaiacol

Copper-based catalysts are widely employed in the catalytic conversion of aromatic compounds to phenolic derivatives. However, single-atom copper catalysts often exhibit limited reactivity and stability. In this study, we addressed these limitations by loading Cu onto NaY zeolite via ion exchange to synthesize a CuY catalyst, followed by Yb modification. By optimizing the Yb content, we significantly enhanced the anisole conversion rate and guaiacol yield. Catalyst characterization revealed that Yb species modulate the electronic structure of copper, favoring the formation of abundant Cu+ species. This electronic modification promotes the catalytic generation of hydroxyl radicals (˙OH) from hydrogen peroxide, thereby accelerating the reaction kinetics. Furthermore, Yb incorporation into CuY induced the formation of oxygen vacancies, which improved hydroxyl radical adsorption and facilitated the generation of metal-oxo species. These synergistic effects collectively increased the reaction's overall conversion efficiency. Under optimized reaction conditions, the Yb/CuY catalyst achieved an anisole conversion of 56.2% and an ortho-selectivity of 74.6%, clearly outperforming previous reports.

Reactive species in peracetic acid-based AOPs: A critical review of their formation mechanisms, identification methods and oxidation performances

The efficient removal of emerging micropollutants poses significant challenges in wastewater treatments. Advanced oxidation processes (AOPs) are extensively studied in the field, and peracetic acid (PAA) has attracted great attention as an alternative oxidant in recent years. Various reactive species yield in PAA-based AOPs, which are regarded as the promising approaches for pollutants elimination. This review systematically investigates the formation pathways, identification methods and oxidation performances of the reactive species in PAA-based AOPs, putting focus on the organic radicals such as CH3C(O)O•, CH3C(O)OO•, CH3OO• and •CH3. Firstly, the formation pathways of reactive species induced by PAA activation are outlined. Then the specific probes and quenchers used for the identification of reactive species are summarized, and the commonly used methods are described and discussed. The reaction kinetics and mechanisms of reactive species and compounds are compared, indicating that the oxidation performances of organic radicals are mainly depended on the properties of radicals and the structure of compounds. Finally, the prospects on further research of PAA-based AOPs are proposed. This article provides a comprehensive overview of organic radicals for the first time, which can serve useful reference for ongoing studies in PAA-based AOPs.

Photocatalytic Oxidation of Benzene to Phenol with O2 over WO3 Treated by Vacuum-Sealed Annealing

Photocatalytic oxidation of benzene to phenol using molecular O2 is one of the most promising sustainable approaches for the green synthesis of phenol. Introducing oxygen vacancies (OVs) on semiconductor surfaces by defect engineering is a promising strategy to enhance the efficiency of benzene oxidation to produce phenol due to the unique functions of OVs in facilitating the charge separation and activation of molecular O2. Herein, a vacuum-sealed annealing strategy has been well developed to generate abundant surface OVs on semiconductors, such as WO3. The well-sealed quartz vial creates a well-controlled low-pressure condition for the formation of OVs without the need for external energy for maintaining the vacuum state. Moreover, the gaseous species generated during the thermal annealing process help mitigate stress-induced defects, particularly bulk defects. The vacuum-sealed annealed WO3 with sufficient OVs and reduced bulk defects shows a better photocatalytic performance in the one-step oxidation of benzene to phenol with O2, compared to the WO3 synthesized through thermal annealing in Ar and H2 atmospheres. The present vacuum-sealed annealing strategy is found to be further applicable to engineer a wide range of semiconducting photocatalysts with abundant OVs to optimize their properties for efficient photocatalysis and other OV-promoted systems.

New insights into the pH-dependent removal of sulfamethoxazole in peracetic acid activation systems: From mechanistic exploration to practical application potentials

Peracetic acid (PAA) as emerging oxidant in advanced oxidation processes (AOPs) has attracted widespread attention in purifying water pollution. In this research, the removal of target contaminant (sulfamethoxazole, SMX) was investigated through PAA activation by a facile catalyst (Co@C), and the active sites of catalyst were identified as sp3-C, Oads, and Co0 by correlation analysis. Especially, different pH adjustment strategies were designed, including System A (adjusting pH after adding PAA) and System B (adjusting pH before adding PAA), to investigate the impact of oxidant acidity and alkalinity on solution microenvironment as well as effect and mechanism of pollutant removal. The results showed that HO· and CH3C(O)OO· dominated in System A, while Co(IV)O2+ was also observed in System B. Both systems showed optimal SMX degradation (98 %). However, System A exhibited excellent water quality tolerance (efficiency > 78 %), superior sustained catalyst activation (efficiency > 80 % in 40 h), less ion leaching (41 μg L-1), and lower products toxicity. Moreover, the pH of solution after reaction in System B was intensely acidic, requiring costly pH adjustments for discharge. This study unveils the strategy of adjusting pH after adding PAA is preferable for water purification, enriching the emerging research of PAA-based AOPs for the remediation of environments.

Vanadium-Silsesquioxane Nanocages as Heterogeneous Catalysts for Synthesis of Quinazolinones

The functionalization of polyoxovanadate clusters is promising but of great challenge due to the versatile coordination geometry and oxidation state of vanadium. Here, two unprecedented silsesquioxane ligand-protected "fully reduced" polyoxovanadate clusters were fabricated via a facial solvothermal methodology. The initial mixture of the two polyoxovanadate clusters with different colors and morphologies (green plate V14 and blue block V6) was successfully separated as pure phases by meticulously controlling the assembly conditions. Therein, the V14 cluster is the highest-nuclearity V-silsesquioxane cluster to date. Moreover, the transformation from a dimeric silsesquioxane ligand-protected V14 cluster to a cyclic hexameric silsesquioxane ligand-protected V6 cluster was also achieved, and the possible mechanism termed "ligand-condensation-involved dissociation reassembly" was proposed to explain this intricate conversion process. In addition, the robust V6 cluster was served as a heterogeneous catalyst for the synthesis of important heterocyclic compounds, quinazolinones, starting from 2-aminobenzamide and aldehydes. The V6 cluster exhibits high activity and selectivity to access pure quinazolinones under mild conditions, where the high selectivity was attributed to the confinement effect of the macrocyclic silsesquioxane ligand constraining the molecular freedom of the reaction species. The stability and recyclability as well as the tolerance of a wide scope of aldehyde substrates endow the V6 cluster with a superior performance and appreciable potential in catalytic applications.

Copper-containing POM-based hybrid P2Mo22V4Cu4 nanocluster as heterogeneous catalyst for the light-driven hydroxylation of benzene to phenol

The current traditional phenol production process has many shortcomings, and the efficient and clean photocatalytic one-step oxidation to phenol is gradually attracting attention. Heteropolyacids (PMo10V2) with high-density Lewis acid active sites and excellent photoelectron transfer ability are ideal choices for catalytic reactions. In this study, a copper-modified isolated dimeric hybrid nanocluster, [Cu(pyim)2]2[Cu(pyim)2(P2MoVI20MoV2VIV4O82)]2·(H2O) (pyim = [2-(pyridin-2-yl)imidazole]), was synthesized by a convenient hydrothermal method. The structural analysis demonstrated that the compound was composed of metal-organic complexes containing pyim ligands, Keggin-type heteropolyacids, and transition metal copper ions. Remarkably, this not only solves the difficulty that the heteropolymeric acid cannot be recovered by dissolving in the solvent but also introduces the copper atom as a second active center. The catalyst exhibited a benzene conversion of 15.6% and a selectivity of 85.2% in a mixed solution of acetonitrile and acetic acid under optimal reaction conditions. After four catalytic cycles, the PXRD pattern proved that the catalyst was still stable. This study provides a good idea for photocatalytic reactions and other environmental applications.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.

Room temperature removal of high-space-velocity formaldehyde boosted by fixing Pt nanoparticles into Beta zeolite framework

Catalytic oxidation of volatile organic compounds like formaldehyde (HCHO) over the noble metals catalysts at room temperature is among the most promising strategies to control indoor pollution but remains one challenge to maximize the efficiency of noble metal species. Herein, we demonstrated the straightforward encapsulation of highly dispersive Pt nanoparticles (NPs) within BEA zeolite and adjacent with the surface hydroxyl groups to reach the synergistic HCHO oxidation at 25 °C. High efficiency and long-term stability was reached under large space velocity (∼100% conversion at 180,000 mL (g_cat × h)^-1 and >95% at 360,000 mL (g_cat × h)^-1), affording rapid elimination rate of 129.4 μmol (g_Pt × s)^-1 and large turnover frequency of 2.5 × 10^-2 s^-1. This is the first synergy example derived from the hydroxyl groups and confined noble metals within zeolites that accelerated the rate-determining step, the formate transformation, in the HCHO elimination.

Insights into the mechanism of carbocatalysis for peracetic acid activation: Kinetic discernment and active site identification

Peracetic-acid-based advanced oxidation processes (PAA-AOPs) on metal-free catalysts have emerged as charming strategies for water contaminant removal. However, the involved reactive species and their corresponding active sites are ambiguous. Herein, using carbon nanotube (CNT) as a model carbocatalyst, we demonstrated that, under neutral conditions, the CNT-PAA* complex was the dominant reactive species to oxidize phenolic compounds via electron-transfer process (ETP), whereas the surface-bound hydroxyl radicals (^·OH_surface) played a minor role on the basis of quenching and electrochemical tests as well as Raman spectroscopy. More importantly, the experimental and density functional theory (DFT) calculation results collaboratively proved that the active site for ETP was the sp²-hybridized carbon on the CNT bulk, while that for radical generation was the edge-located hydroxyl group (C-OH), which lowered the energy barrier for cleaving the O-O bond in CNT-PAA* complex. We further discerned the oxidation kinetic constants (k_oxid) of different pollutants from the apparent kinetic constants in CNT/PAA system. The significant negative linear correlation between lnk_oxid and half-wave potential of phenolic compounds suggests that the pollutants with a lower one-electron oxidation potential (i.e., stronger electron-donating ability) are more easily oxidized. Overall, this study scrutinizes the hybrid radical and non-radical mechanism and the corresponding active sites of the CNT/PAA system, providing insights into the application of PAA-AOPs and the development of ETP in the remediation of emerging organic pollutants.

Application of Raw and Chemically Modified Biomasses for Heterogeneous Cu-Catalysed Conversion of Aryl boronic Acids to Phenols Derivatives

This work describes the application of raw and chemically modified cellulose and sugarcane bagasse for ipso-hydroxylation of aryl boronic acids in environmentally friendly reaction conditions. The catalytic efficiency of five support-[Cu] materials was compared in forming phenols from aryl boronic acids. Our investigation highlights that the CEDA-[Cu] material (6-deoxy-6-aminoethyleneamino cellulose loaded with Cu) leads to the best results under very mild reaction conditions. The optimized catalytic sequence, allowing a facile transformation of boronic acids to phenols, required the mandatory and joint presence of the support, Cu2O, and KOH at room temperature. CEDA-[Cu] was characterized using 13C solid-state NMR, ICP, and FTIR. The use of CEDA-[Cu] accounts for the efficacious synthesis of variously substituted phenol derivatives and presents very good recyclability after five catalytic cycles.

Reusable citric acid modified V/AC catalyst prepared by dielectric barrier discharge for hydroxylation of benzene to phenol

A reusable and efficient citric acid modified V/AC catalyst for benzene hydroxylation was prepared using an environmentally benign DBD method.

Hydroxylation of benzene to phenol over heteropoly acid H5PMo10V2O40 supported on amine-functionalized MCM-41

Supported catalysts with Keggin type heteropoly acids (H5PMo10V2O40) loaded onto amine-functionalized MCM-41 for the catalytic hydroxylation of benzene to phenol with H2O2 were prepared by a wet impregnation method. The effects of the preparation conditions on the properties and activity of the supported catalysts were fully investigated. The results showed that the catalyst retained the mesoporous structure of MCM-41 and H5PMo10V2O40 was dispersed uniformly on the surface of the amine-functionalized MCM-41. Meanwhile, the reusability and catalytic performance of the catalyst were affected by two key factors, i.e., the interaction between the heteropoly acid and the surface of MCM-41, and the hydrophobicity of the catalyst since they decide the leaching of H5PMo10V2O40 and the adsorption of benzene. The catalyst with H5PMo10V2O40 loaded onto amine-functionalized MCM-41, which was prepared using ethanol as the solvent, exhibited the highest phenol yield (20.4%), a turnover frequency value of 20.3 h-1 and good reusability. We believe this work offers an effective and facile strategy for the preparation of a new catalyst for hydroxylation of benzene to phenol.

On the application of 3d metals for C-H activation toward bioactive compounds: The key step for the synthesis of silver bullets

Several valuable biologically active molecules can be obtained through C-H activation processes. However, the use of expensive and not readily accessible catalysts complicates the process of pharmacological application of these compounds. A plausible way to overcome this issue is developing and using cheaper, more accessible, and equally effective catalysts. First-row transition (3d) metals have shown to be important catalysts in this matter. This review summarizes the use of 3d metal catalysts in C-H activation processes to obtain potentially (or proved) biologically active compounds.

Self-assembled iron-containing mordenite monolith for carbon dioxide sieving

The development of low-cost, efficient physisorbents is essential for gas adsorption and separation; however, the intrinsic tradeoff between capacity and selectivity, as well as the unavoidable shaping procedures of conventional powder sorbents, greatly limits their practical separation efficiency. Herein, an exceedingly stable iron-containing mordenite zeolite monolith with a pore system of precisely narrowed microchannels was self-assembled using a one-pot template- and binder-free process. Iron-containing mordenite monoliths that could be used directly for industrial application afforded record-high volumetric carbon dioxide uptakes (293 and 219 cubic centimeters of carbon dioxide per cubic centimeter of material at 273 and 298 K, respectively, at 1 bar pressure); excellent size-exclusive molecular sieving of carbon dioxide over argon, nitrogen, and methane; stable recyclability; and good moisture resistance capability. Column breakthrough experiments and process simulation further visualized the high separation efficiency.

Light-Induced Efficient Hydroxylation of Benzene to Phenol by Quinolinium and Polyoxovanadate-Based Supramolecular Catalysts

Direct Hydroxylation of benzene to phenol with high yield and selectivity has been the goal of phenol industrial production. Photocatalysis can serve as a competitive method to realize the hydroxylation of benzene to phenol owing to its cost-effective and environmental friendliness, however it is still a forbidding challenge to obtain good yield, high selectivity and high atom availability meanwhile. Here we show a series of supramolecular catalysts based on alkoxohexavanadate anions and quinolinium ions for the photocatalytic hydroxylation of benzene to phenol under UV irradiation. We demonstrate that polyoxoalkoxovanadates can serve as efficient catalysts which can not only stabilize quinolinium radicals but also reuse H₂ O₂ produced by quinolinium ions under light irradiation to obtain excellent synergistic effect, including competitive good yield (50.1 %), high selectivity (>99 %) and high atom availability.

Monomeric vanadium oxide: a very efficient species for promoting aerobic oxidative dehydrogenation of N-heterocycles

The isolated monomeric VO₄ species, controlled by natural ligand tartaric acid, in the VO_x/NbO_y@C catalysts exhibited excellent performances and good recyclability in the dehydrogenation of N-heterocycles.

Theoretical study on molecular mechanism of aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformyfuran catalyzed by VO2+ with counterpart anion in N,N-dimethylacetamide solution

Vanadium-containing catalysts exhibit good catalytic activity toward the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformyfuran (DFF). The aerobic oxidation mechanism of HMF to DFF catalyzed by VO₂⁺ with counterpart anion in N,N-dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO₂⁺-containing complex is the four-coordinated [V(O)₂(DMA)₂]⁺ species. For the gross reaction of 2HMF + O₂ → 2DFF + 2H₂O, there are three main reaction stages, i.e., the oxidation of the first HMF to DFF with the reduction of [V(O)₂(DMA)₂]⁺ to [V(OH)₂(DMA)]⁺, the aerobic oxidation of [V(OH)₂(DMA)]⁺ to the peroxide [V(O)₃(DMA)]⁺, and the oxidation of the second HMF to DFF with the reduction of [V(O)₃(DMA)]⁺ to [V(O)₂(DMA)₂]⁺. The rate-determining reaction step is associated with the C–H bond cleavage of –CH₂ group of the first HMF molecule. The peroxide [V(O)₃(DMA)]⁺ species exhibits better oxidative activity than the initial [V(O)₂(DMA)₂]⁺ species, which originates from its narrower HOMO–LUMO gap. The counteranion Cl⁻ exerts promotive effect on the aerobic oxidation of HMF to DFF catalyzed by [V(O)₂(DMA)₂]⁺ species.

The rate-determining reaction step is associated with the C–H bond cleavage of –CH₂ group of the first HMF molecule oxidized by [V(O)₂(DMA)₂]⁺ species, while counteranion Cl⁻ exhibits catalytically promotive effect.

Product-oriented Direct Cleavage of Chemical Linkages in Lignin

Lignin is one of the most important biomacromolecules in the plant biomass and the largest renewable source of aromatic building blocks in nature. Selectively producing value-added chemicals from the catalytic transformation of renewable lignin is of strategic significance and meet sustainability targets owing to the excessive consumption of non-renewable petroleum resource, but remains a long-term challenge owing to the complexity of lignin structure. This Minireview provides a summary and perspective of the extensive research that provides insight into selectively catalytic transformations of lignin and its derived monomers via directed scissor of chemical linkages (C-O and C-C bonds) with product-oriented targets. Furthermore, some challenges and opportunities of lignin catalytic transformation are provided based on existing problems in this field for readers to discuss future research directions.

Oxidative desulfurization of model oil over Ta-Beta zeolite synthesized via structural reconstruction

As to metallosilicate zeolites, ions with larger size such as Ta⁵⁺ in the gels greatly retarded their crystallization during the hydrothermal synthesis, affording long-winded synthesis periods, up-limited framework-substituted metal contents, or even frustrated outcome. An efficient hydrothermal synthesis strategy for metallosilicate, in this case of Ta framework-substituted *BEA zeolite, via structural reconstruction was proposed to stride the gap. The Ta content in our developed Ta-Beta-Re-50 zeolite achieved up to 5.48 % (Si/Ta = 52), breaking through the limitation of Ta contents for conventional method (Si/Ta > 100). Additionally, this Ta-Beta-Re zeolite possessed nanosized crystals (20-40 nm) and short crystallization time (8 h), significantly improving space-time yields of practical zeolite production. Through spectroscopic study, it was confirmed that the existence of zeolite structural units intensively facilitated the formation of nucleation and crystal growth. This innovative Ta-Beta zeolite demonstrated high catalytic performances for oxidation desulfurization, far outperforming traditional fluoride-mediated Ta-Beta-F, which was ascribed to its excellent diffusion properties and incredible high isolated Ta contents. Additionally, the catalytic performance of Ta-Beta-Re could be regenerated after simple calcination and the deactivation may be caused by pore blocking of organics. This work provides a new method for rationally design and construction of metallosilicate materials with high activity for catalytic oxidation applications, which can bridge the conceptual and technical gap between periodic trends and zeolite material synthesis.

In Situ Encapsulation of Pt Nanoparticles within Pure Silica TON Zeolites for Space-Confined Selective Hydrogenation

Straightforward encapsulation of Pt clusters (∼2 nm) into the pure silica TON-type zeolite (ZSM-22) was reached in a dry gel conversion route, where the ionic liquid template was removed via the hydrocracking-calcination-reduction approach. The obtained Pt@ZSM-22 series possessed high crystallinity, large surface area, and ultrafine Pt clusters inside the zeolite crystals. They exhibited remarkable activity in the semi-hydrogenation of phenylacetylene into styrene; the lead sample with 0.2 wt % Pt loading afforded a large turnover number up to 117,787. The preferential high affinity of the pure silica ZSM-22-encapsulated Pt clusters toward the substrate phenylacetylene rather than the hydrogenated product was derived from the unique space-confinement effect of zeolite microchannels, which is responsible for such excellent performance.

Catalytic mechanisms of oxygen-containing groups over vanadium active sites in an Al-MCM-41 framework for production of 2,5-diformylfuran from 5-hydroxymethylfurfural

In the V-doped Al-MCM-41 framework, the [V-1] active site with a hydroxyl group displays better catalytic activity than the [V-0] active site without a hydroxyl group toward the oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran.

Zeolite encapsulated Ni(ii) Schiff-base complexes: improved catalysis and site isolation

Site isolation and distorted geometry of the zeolite encapsulated complex govern the improved catalysis for phenol hydroxylation reaction.

Catalyst- and solvent-free ipso-hydroxylation of arylboronic acids to phenols

A catalyst-free method for the hydroxylation of arylboronic acids to form the corresponding phenols with sodium perborate as the oxidant was developed using water as the solvent. Under the reaction conditions, the yield of phenol reached 92% at only 5 min. Moreover, the reaction could be conducted without a catalyst under the solvent-free condition, the efficiency of which was as high as that of a liquid-phase reaction. Using a microcalorimeter, the reaction was found to be an exothermic reaction. The reaction mechanism was investigated and understood via DFT calculations, which revealed that it was a nucleophilic reaction.

A new iron-based metal-organic framework with enhancing catalysis activity for benzene hydroxylation

A new Fe-based metal-organic framework (MOF), termed Fe-TBAPy Fe2(OH)2(TBAPy)·4.4H2O, was solvothermally synthesized. Structural analysis revealed that Fe-TBAPy is built from [Fe(OH)(CO2)2]∞ rod-shaped SBUs (SBUs = secondary building units) and 1,3,6,8-tetrakis(p-benzoate)pyrene (TBAPy4-) linker to form the frz topological structure highlighted by 7 Å channels and 3.4 Å narrow pores sandwiching between the pyrene cores of TBAPy4-. Consequently, Fe-TBAPy was used as a recyclable heterogeneous catalyst for benzene hydroxylation. Remarkably, the catalysis reaction resulted in high phenol yield and selectivity of 64.5% and 92.9%, respectively, which are higher than that of the other Fe-based MOFs and comparable with those of the best-performing heterogeneous catalysts for benzene hydroxylation. This finding demonstrated the potential for the design of MOFs with enhancing catalysis activity for benzene hydroxylation.

Ordered Porous Poly(ionic liquid) Crystallines: Spacing Confined Ionic Surface Enhancing Selective CO2 Capture and Fixation

Porous poly(ionic liquid)s (PPILs) combine the features of porous materials, polymers, and ionic liquids (ILs) or their derivatives, but they are normally of amorphous structure with disordered pores. Here, we report the facile synthesis of ordered porous poly(ionic liquid) crystallines (OPICs, specialized as a kind of PPIL analogues) with diverse and adjustable framework IL moieties through the Schiff base condensation of IL-derived ionic salts and neutral monomers. Ternary monomer mixtures are employed to artistically control the chemical composition and pore configurations. Compact atomic packing was achieved to give spacing confined ionic surface with strong CO₂ affinity. Through monomer control, OPICs exhibit high CO₂ uptakes with excellent CO₂/N₂(CH₄) selectivities and efficiently implement CO₂ fixation through catalyzing epoxides cycloaddition under down to ambient conditions.

Quinone-amine polymers as metal-free and reductant-free catalysts for hydroxylation of benzene to phenol with molecular oxygen

Quinone-amine polymers can be employed as a metal-free and reductant-free catalyst for the hydroxylation of benzene to phenol and can yield phenol as high as the transition metal catalyst.