Selective oxidation of methane to methanol under mild conditions remains a long-standing challenge because of the high inertness of the C-H bond in methane and the susceptibility of methanol to overoxidation. Here, we report a nitrogen-incorporation strategy for constructing TiO2-supported Au catalysts with cationic Au sites for selective methane oxidation using O2 as the oxidant in aqueous CH4/O2/CO media. The optimized Au/N-TiO2 catalyst delivers a methanol productivity of 3956 mu mol gcat -1 h-1, corresponding to 177 mol molAu -1 h-1, with 98% selectivity at 180 degrees C, demonstrating superior catalytic performance to most reported systems under comparable conditions. Spectroscopic and structural analyses reveal that nitrogen incorporation modulates the electronic state of Au and, in combination with an appropriate Au particle size, establishes a favorable size-charge match for constructing highly efficient interfacial active sites. Isotope-labeling experiments, in situ DRIFTS, kinetic analysis, and density functional theory calculations show that the reaction proceeds through a CO-assisted, surface-mediated O2 activation pathway involving surface methoxy species as key intermediates.

The selective hydrogenation of 1,3-butadiene to 1-butene represents a pivotal process in the purification of industrial olefin streams, yet its performance is often hindered by undesired 1-butene isomerization to 2-butene. Herein, we employ parahydrogen-induced polarization (PHIP) nuclear magnetic resonance (NMR) spectroscopy as a pathway-sensitive probe to unravel the mechanistic origin of this isomerization. Pd-Au alloy nanoparticles supported on TiO2 with systematically tuned Pd/Au mass fractions reveal a distinct mechanistic transition governing 1-butene reactivity. Combined PHIP NMR, CO diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS), and quasi-in situ X-ray photoelectron spectroscopy (XPS) analyses demonstrate that on contiguous Pd ensembles, 1-butene isomerization is primarily driven by hydrogen surface coverage. Progressive incorporation of Au into the alloy disrupts these Pd ensembles, generating isolated Pd sites that shift the reaction control toward a competitive adsorption regime, wherein preferential 1,3-butadiene adsorption effectively suppresses 1-butene isomerization. Under reaction conditions, carbonaceous restructuring further stabilizes the single-atom Pd species, reinforcing the inhibition of isomerization.

Understanding the distinct roles of Brønsted and Lewis acid sites remains a great challenge in designing zeolite catalysts, as their coexistence often obscures mechanistic understanding. Here, we combine solid-state NMR spectroscopy with density functional theory to elucidate the site-specific pathways of ethanol dehydration to ethylene over ZSM-5 zeolite. Two key intermediates are identified: chemisorbed ethanol on Lewis acid sites (LAS) and surface ethoxy species on Brønsted acid sites (BAS), both formed via -OH activation followed by β-H elimination to yield ethylene. Comparative analysis reveals a thermodynamic-kinetic trade-off between the two sites. LAS facilitates low-temperature -OH activation but exhibits high barriers for β-H elimination, limiting ethylene formation. In contrast, BAS requires higher activation energy for -OH activation but enables more facile β-H elimination, promoting ethylene production. This intrinsic trade-off, governed by the thermodynamics of -OH activation, provides a mechanistic basis for understanding and tuning alcohol dehydration on zeolite acid sites.

Selective oxidation of methane to methanol under mild conditions remains a long-standing challenge because of the high inertness of the C-H bond in methane and the susceptibility of methanol to overoxidation. Here, we report a nitrogen-incorporation strategy for constructing TiO2-supported Au catalysts with cationic Au sites for selective methane oxidation using O2 as the oxidant in aqueous CH4/O2/CO media. The optimized Au/N-TiO2 catalyst delivers a methanol productivity of 3956 μmol gcat-1 h-1, corresponding to 177 mol molAu-1 h-1, with 98% selectivity at 180 °C, demonstrating superior catalytic performance to most reported systems under comparable conditions. Spectroscopic and structural analyses reveal that nitrogen incorporation modulates the electronic state of Au and, in combination with an appropriate Au particle size, establishes a favorable size-charge match for constructing highly efficient interfacial active sites. Isotope-labeling experiments, in situ DRIFTS, kinetic analysis, and density functional theory calculations show that the reaction proceeds through a CO-assisted, surface-mediated O2 activation pathway involving surface methoxy species as key intermediates.

The synergistic interplay between Br & oslash;nsted and Lewis acid sites in zeolites plays a key role in biomass conversion, yet direct assessment of such site cooperation remains challenging. Here, advanced two-dimensional solid-state NMR spectroscopy combined with probe-molecule analysis is employed to directly identify and semiquantitatively quantify proximate Br & oslash;nsted/Lewis acid site pairs in Sn-Al-beta zeolites for glucose conversion. By tuning the Sn/Al ratio, the abundance of framework Sn-derived Lewis acid sites is varied while maintaining comparable Br & oslash;nsted acidity, enabling the effect of acid-site proximity to be disentangled. H-1-P-31 and P-31-P-31 correlation NMR experiments reveal the spatial proximity between Br & oslash;nsted acid sites and framework Sn-derived Lewis acid sites and show that neighboring Lewis acid sites are associated with enhanced Bro/nsted acidity. The estimated concentration of BAS-LAS pairs correlates strongly with the apparent initial methyl levulinate formation rate, whereas the total BAS or LAS concentrations alone do not capture the same trend.

The concept of metal-ligand bifunctional catalysts has been extensively explored in homogeneous catalysis, yet it has not been reported in conventional heterogeneous catalysis. Inspired by the outer-sphere hydrogenation mechanism in homogeneous metal-ligand bifunctional catalysts, we here find that an Ir single-atom catalyst with a predominantly Ir1-P4 coordination structure behaves as a heterogeneous metal-ligand bifunctional catalyst exclusively favoring the hydrogenation of the C═O bond over the C═C bond in α,β-unsaturated aldehydes─an industrially important but highly challenging transformation. The hydrogenation process is revealed to proceed through a Noyori-type transition state during the 1,2-addition pathway at the Ir-P bifunctional sites, as evidenced by combining the in situ two-dimensional 1H-1H spin diffusion and 1H-31P heteronuclear correlation nuclear magnetic resonance spectroscopy, apparent reaction order test, kinetic isotope effect analysis, and density functional theory calculations. This work demonstrates a new type of heterogeneous metal-ligand bifunctional catalyst for the chemoselective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols and sheds light on the hydrogenation mechanism.

The oxygen reduction reaction (ORR) activity of earth-abundant transition-metal (TMOs) oxides is limited by inefficient interfacial charge transfer and unfavorable surface adsorption. Here, we report pyridine-isomerism-driven interfacial spin-engineering in covalent organic polymer (COP)-Fe3O4 hybrids, where molecularly defined pyridinic environments program the electronic/spin structure of Fe3O4 nanocrystals. Using 2,3- and 3,4-diaminopyridine as isomeric building blocks, we construct pyridinic-rich COPs that anchor Fe3O4 and selectively tune metal-polymer interaction. The 2,3-COP positions the pyridinic N adjacent to the & horbar;C & boxH;C & horbar;N & horbar; linkage, strengthening COP-Fe3O4 interactions, enhancing interfacial electron withdrawal, and inducing a low- to intermediate-spin transition of Fe species. Spectroscopic analysis corroborates this reconfiguration, which upshifts the Fe d-band center, enriches unpaired electrons, and optimizes Fe-O covalency, thereby lowering the barrier for OOH* activation and promoting a selective four-electron ORR pathway with improved stability. Consequently, the designed 2,3-COP-Fe3O4 electrocatalyst exhibits a stable half-wave potential of 0.890 V in alkaline electrolyte, outperforming the noble-metal benchmark. Moreover, when implemented in aqueous Zn-air batteries, it delivers a maximum power density of 315.4 mW cm-2 and maintains stable operation for over 800 h at 10 mA cm-2, exceeding most reported systems. These findings establish pyridine-isomerism-directed spin-engineering as a versatile and scalable platform for designing applicable high-performance TMO-based electrocatalysts.

Amorphous silica-aluminas (ASAs) are widely used catalysts, with a distribution of Brønsted acid sites (BAS), that yield unique catalytic properties exploited in numerous industrial settings. While having atomic-level insight into their structures, in particular their interfacial sites, would be key to enable rational design, these sites are notoriously difficult to characterize due to spectral complexity arising from a diversity of hydroxyls and the overwhelming interference from noninterfacial signals. Herein, we introduce a 27Al-filtered 1H-1H double-quantum/single-quantum NMR (f-DQ/SQ) spectroscopy method integrated with DFT calculations to probe hydroxyls at solid-state interfaces selectively. Combined with probe molecule (acetone and TMP) adsorption experiments, this approach unequivocally demonstrates that hydrothermal post-treatment increases BAS density in ASA. Dynamic-nuclear-polarization-enhanced 29Si-{27Al} D/J-based correlation experiments corroborate the rearrangement process at the silica-alumina interface, while the heteronuclear-filtered 1H-1H DQ/SQ NMR reveals that the increase in BAS density originates from the formation of specific pseudobridged silanol (PBS) pairs─a distinction imperceptible in conventional 1H or 1H-{27Al} correlation NMR. PBS pairs constitute ca. 73% of the total PBS population, estimated by a semiquantitative analysis combining 27Al-filtered experiments and spin-dynamics simulations. Through a time-dependent 1H-1H f-DQ/SQ variant, we quantified key interatomic distances (∼2 Å for H-H and ∼4.1 Å for H-Al) within these PBS motifs. Constrained DFT calculations ultimately identify a vicinal-silanol-derived configuration as the most stable PBS structure, being 294 kJ/mol lower in relative energy, thereby resolving the atomic-scale origin of augmented acidity in hydrothermally treated ASAs.

The synergistic interplay between Brønsted and Lewis acid sites in zeolites plays a key role in biomass conversion, yet direct assessment of such site cooperation remains challenging. Here, advanced two-dimensional solid-state NMR spectroscopy combined with probe-molecule analysis is employed to directly identify and semiquantitatively quantify proximate Brønsted/Lewis acid site pairs in Sn-Al-β zeolites for glucose conversion. By tuning the Sn/Al ratio, the abundance of framework Sn-derived Lewis acid sites is varied while maintaining comparable Brønsted acidity, enabling the effect of acid-site proximity to be disentangled. 1H-31P and 31P-31P correlation NMR experiments reveal the spatial proximity between Brønsted acid sites and framework Sn-derived Lewis acid sites and show that neighboring Lewis acid sites are associated with enhanced Bro̷nsted acidity. The estimated concentration of BAS-LAS pairs correlates strongly with the apparent initial methyl levulinate formation rate, whereas the total BAS or LAS concentrations alone do not capture the same trend.

Abstract CO2-assisted oxidative dehydrogenation of ethane (CO2-ODHE) offers a promising route for the simultaneous valorization of CO2 and light alkanes to produce value-added ethylene. However, the cooperative activation of both C–H and C=O bonds along with severe coking remains a major bottleneck. Herein, we demonstrate that oxygen vacancies (OV) on (002)-faceted ZnO nanoplates tune adsorption selectivity between CO2 and C2H6. The OV densities increase with (002) facet exposure, thereby reversing the adsorption selectivity from CO2-dominant at low densities to C2H6-dominant at high densities. This OV-mediated adsorption behavior ensures balanced activation of both reactants, with CO2 precisely activated at OV sites and ethane C–H bonds selectively cleaved at Zn–O–Zn sites. Consequently, the optimized catalyst delivers an average C2H4 yield of 10.3% over the last 100 min of a 5 h reaction at 600 °C, which is better than that of most reported noble metal-based catalysts, while maintaining stable cycling performance. This work establishes facet-regulated oxygen vacancies as an effective defect strategy for synergistic C–H and C=O bond activation toward rational catalyst design.

In situ solid-state nuclear magnetic resonance (NMR) serves as a powerful means to study catalytic reactions under operating conditions. Standard solid-state NMR rotors typically struggle to match the pressure and temperature of active reactions during sampling. Here, we introduce specialized inserts for commercial solid-state NMR rotors capable of withstanding pressures from atmospheric to 618.3 kPa and temperatures ranging from room temperature up to 433 K. With this innovative design, we examine the isomerization of dihydroxyacetone (DHA) on Sn-MFI zeolite catalyst using in situ 1H MAS NMR, revealing the presence of a gem-diols-type intermediate during the transformation of DHA into glyceraldehyde.

The selective oxidation of methane to form methanol and acetic acid has been studied using AuPd nanoparticles supported on the zeolite H-ZSM-5 in water at 240 degrees C using molecular oxygen as the terminal oxidant in the absence of any added coreductant. The addition of Pd to Au/ZSM-5 significantly increases the selectivity to acetic acid to levels approaching almost complete selectivity within the oxygenated products. However, we observe that the reaction conditions employed lead to the corrosion of the stainless-steel components of the autoclave reactor and also leaching of iron from the ZSM-5 zeolite, and hence the AuPd nanoparticles, on reaction, become coated or partially coated with an oxidic Fe shell. The presence of the oxidized iron coating hinders nanoparticle agglomeration preventing deactivation of the AuPd/ZSM-5 catalyst but does not adversely affect the observed catalysis.

Cyclopentenyl cations, crucial intermediates in zeolite-catalyzed hydrocarbon transformations, exhibit unique dual hydrophobicity-hydrophilicity due to their polar cationic centers and nonpolar alkyl groups. This study investigates their regional hydrophobicity under moist environments using multidimensional solid-state NMR spectroscopy with propane as a probe molecule. We demonstrate that water enhances noncovalent interactions between cyclopentenyl cations and propane in ZSM-5 channels, primarily through the alkyl groups, confirming their regional hydrophobic character. Competitive adsorption experiments using dichloromethane (dielectric constant, ε = 8.9) further highlight the critical role of solvent polarity (εwater = 80.1) in promoting hydrophobic interactions. A surfactant-like assembly mechanism is proposed, where water repels propane from Brønsted acid sites in zeolite, driving its accumulation near hydrophobic alkyl regions.

The ZSM-5 zeolite is the key active component in high-severity fluid catalytic cracking (FCC) catalysts and is routinely activated by phosphorus compounds in industrial production. To date, however, the detailed structure and function of the introduced phosphorus still remain ambiguous, which hampers the rational design of highly efficient catalysts. In this work, using advanced solid-state NMR techniques, we have quantitatively identified a total of seven types of P-containing complexes in P-modified ZSM-5 zeolite and clearly revealed their structure, location, and catalytic role. The experimental findings indicate that the introduced phosphorus can stabilize a portion of the aluminum atoms in the lattice by forming an energetically favorable framework-bound Si-OH-Al-O-P structure inside the zeolite channels, preserving more acidic bridging hydroxyl groups under the working conditions of the catalyst. Besides, two other types of hydrothermally stable phosphoric acid species (H3PO4 and H4P2O7) captured by neighboring silanol groups (H3PO4HO-Si(SiO4)3 and H4P2O7HO-Si(SiO4)3) are identified. For the FCC process, the framework-bound Si-OH-Al-O-P structure is proven to be the active site in the conversion of the FCC reactant, while the two phosphoric acid species can promote the yield of C2-C4 olefins.

We employ computational modeling to elucidate the distribution, transformation, and framework-protecting role of various La species in zeolite Y (Si/Al = 3). Energy analysis reveals that La3+ ions preferentially occupy the hexagonal prisms (D6R) in the dehydrated framework, while hydration drives their transformation into highly coordinated species, such as [La(H2O)3]3+, [La(OH)(H2O)2]2+, [La(OH)2(H2O)]+, and [La(OH)3] which predominantly reside in the sodalite cages (SOD) and, to a less extent, in the supercages (SUP). Examination of the dynamic evolution process upon hydration shows that La3+ converts into [La(H2O)]3+ in the D6R cage; while it transforms into more stable [La(H2O)3]3+, [La(OH)(H2O)2]2+ and [La(OH)2(H2O)]+ species in the larger SOD cage. However, in the largest SUP cage, [La(OH)2]+ and La(OH)3 can readily convert into [La(OH)]2+ through protonation by nearby Br & oslash;nsted acid sites, resulting in [La(OH)(H2O)2]2+ as the most stable species. Ab initio thermodynamics calculations reveal that reaction conditions critically control the thermodynamic stability distribution of La species in the SOD framework. Our investigation demonstrates that the hydroxylated La species, specifically [La(OH)]2+ and [La(OH)2]+ within SOD cage, exhibit a much stronger stabilizing effect on the zeolite Y framework than La3+, indicating the critical role of the hydroxide ligands in fortifying the zeolite framework against dealumination.

Carbenium ions are critical intermediates in zeolite-catalyzed hydrocarbon transformations; yet, their fundamental reactivity and mechanistic pathways remain incompletely understood, particularly under conditions relevant to practical catalysis. Here, we demonstrate that molecular oxygen─often present in catalytic systems but rarely mechanistically considered─profoundly alters carbenium ion chemistry. Through a combination of solid-state 13C NMR, operando UV-vis, and online mass spectrometry, we show that O2 selectively promotes the oxidative transformation of cyclopentenyl cations via cyclopentenone-type intermediates on ZSM-5 zeolite. This oxygen-mediated pathway enhances the formation of methylated aromatics, modulates reaction selectivity, and accelerates the evolution of polyaromatic species, ultimately impacting the catalyst stability. These effects are consistently observed in both methanol-to-hydrocarbon and ethene conversion over zeolites.

Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries. Here, single [Ga(OH)]2+ ion-exchanged mesoporous hollow-structured ZSM-5 (Ga-MH-ZSM-5) material was prepared, and it shows unprecedented catalytic performance in light alkane aromatization, considering activity, product selectivity and catalytic stability. The average aromatics yields in ethane aromatization at 600 degrees C and WHSV of 0.8 h-1 within 28 hand in propane aromatization at 580 degrees C and WHSV of 1.1 h-1 within 20 h reach similar to 18.4% and similar to 70.8% with benzene, toluene and xylenes (BTX) accounting for similar to 96% and similar to 88% of aromatics, respectively. Ga-MH-ZSM-5-0.41 gave a TON for formation of aromatics (TONaromatics) from propane as high as 57479, whereas the reported catalysts maximally show a TONaromatics of 5514. This also holds true for ethane aromatization; the TONaromatics obtained on Ga-MH-ZSM-5-0.41 was >= 3845 in contrast to <= 392 on reported non-noble metal catalysts. The catalytic activity of Ga-MH-ZSM-5 highly depends on Ga species structures. [Ga(OH)]2+ ions are predominant species at Ga loading <= 0.3 wt%, while more [Ga(OH)2]+ and GaOx oligomers are formed with increasing Ga content. Upon reduction with H2, [Ga(OH)]2+ and [Ga(OH)2]+ are transformed into [GaH]2+ and [GaH2]+ species, which show a propane dehydrogenation rate of 300 and 15 times of that of Br empty set nsted acid sites respectively. The light alkanes are mainly dehydrogenated into light olefins on [GaH]2+ species, and then, oligomerized and cyclized into (alkyl)cycloalkanes on H+ sites, which is followed by possible ring expansion on H+ and sequential dehydrogenations into aromatics primarily on [GaH]2+. (c) 2025, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

This study utilizes advanced solid-state NMR spectroscopy to elucidate the spatial distribution, coordination behavior, and inter-nuclear interactions of boron species in B-MFI zeolites. Through 13C-11B symmetry-based resonance-echo saturation-pulse double-resonance (S-RESPDOR) NMR experiment, we reveal that boron incorporation is preferentially directed by tetrapropylammonium (TPA+) structure-directing agents, with boron predominantly occupying both sinusoidal and straight channels rather than channel intersections. Quantitative analysis further indicates a closer proximity to terminal methyl groups of TPA+ in sinusoidal channels (B-Cγ′: ca. 2.8 Å) (1 Å=0.1 nm) compared to straight channels (B-Cγ: ca. 3.1 Å). Upon dehydration, two-dimensional (2D) 11B multiple-quantum magic-angle spinning (MQMAS) NMR, together with a 2D 1H-11B dipolar-based heteronuclear multiple quantum correlation (D-HMQC) experiment, identifies two distinct trigonal boron species, attributed to framework boron perturbed by proximal silanols, highlighting microenvironmental heterogeneity. Our findings establish that boron siting is template-directed and that dehydration induces distinct speciation, providing atomic-scale insights that are crucial for the rational design of zeolites.