Liuyang Zhang

Titanium-based metal–organic frameworks (Ti-MOFs) are widely investigated for their potential in photocatalytic applications owing to their unique structural and electronic properties. However, the local identity of long-lived photoinduced Ti(III) species remains unresolved. In this study, the nature of photogenerated Ti(III) species in the stable Ti-MOF MUV-10(Ca) was examined by electron paramagnetic resonance (EPR) spectroscopy. The results of X- and Q-band (9/34 GHz) continuous wave (CW) EPR provided unequivocal evidence for the presence of two chemically distinct Ti(III) sites, with the selectivity of Ti(IV) photoreduction governed by the hydration state of the material and the wavelength of the incident light. Consolidation of CW EPR and 1H Davies electron-nuclear double resonance (ENDOR) data allowed us to clearly determine the structure of both centers: one associated with an ideal Ti2Ca2-cluster and another one assigned to the missing-linker defect of the MUV-10(Ca) structure. This first example of such hydration state and wavelength-controlled selectivity in photoactive Ti-MOFs contributes to a deeper understanding of the nature of photoactive centers in Ti-MOFs, highlighting the importance of defect engineering for advanced applications.

S-scheme heterojunctions achieve efficient spatial charge separation via the built-in electric field. However, atomic-level precision in regulating interfacial charge transport and reactant activation remains a significant challenge. Herein, we introduce sulfur vacancies (SVs) into a Bi19Br3S27 S-scheme heterojunction to develop an effective strategy that combines interface engineering with interfacial Lewis acid–base chemistry. The SVs serve dual functions: on the one hand, they shorten adjacent Bi–O bonds, enhancing structural stability. On the other hand, they generate Lewis acid sites that facilitate O2 adsorption. Notably, Lewis acids are capable of coupling with Lewis bases within the COF structure, thereby facilitating Lewis acid–base-mediated interfacial charge transfer. Pyridine adsorption infrared spectroscopy directly confirms the emergence of strong Lewis acid sites following the introduction of SVs. Femtosecond transient absorption, in situ XPS, and Kelvin probe force microscopy collectively reveal the characteristic S-scheme charge-transfer pathway. Furthermore, density functional theory calculations indicate that Lewis acid sites optimize the O2 adsorption configuration. Structural and electronic-state analyses demonstrate that the formation of interfacial Lewis acid–base pairs effectively lowers the charge-transport potential barrier, thereby drastically boosting photocatalytic performance. This work pioneers the integration of Lewis acid–base chemistry into S-scheme heterojunction design, achieving end-to-end regulation from bulk charge separation to surface O2 activation.

Efficient spatial separation of photogenerated charge carriers remains a formidable challenge in photocatalysis. Here, we employ in situ Kelvin probe force microscopy (KPFM) to reveal unexpected electron accumulation on nonpolar {010} facets in wurtzite ZnO platelets (N‐ZnO), which represents a dynamic “electron spillover” process beyond static facet confinement. Crucially, femtosecond transient absorption (fs‐TA) spectroscopy directly captures interfacial electron transfer from polar Zn‐terminated (0001) facets (Zn‐ZnO) to N‐ZnO with a lifetime of 60.82 ps. However, electrons spilling over from Zn‐ZnO to N‐ZnO recombine with the photogenerated holes inherent to N‐ZnO, thereby turning it into a recombination center. Guided by this insight, we construct a dual‐cocatalyst architecture (AuZnOCo): Au is selectively anchored on N‐ZnO and Zn‐ZnO to extract electrons, and Co ₃ O ₄ is deposited on O‐terminated (000) facets (O‐ZnO) to trap holes. The loading of dual cocatalysts promotes charge separation and suppresses this electron spillover‑induced recombination. Quantitative analysis reveals ≈3739 holes localized on O‐ZnO, ≈1771 electrons on Zn‐ZnO, and ≈812 electrons on N‐ZnO in AuZnOCo, while the electron diffusion length ( L ) increases from 81.41 to 121.77 nm. This work deciphers the spatiotemporal resolution of charge‐carrier dynamics, offering a blueprint for rationally engineering anisotropic photocatalysts.

Efficient spatial separation of photogenerated charge carriers remains a formidable challenge in photocatalysis. Here, we employ in situ Kelvin probe force microscopy (KPFM) to reveal unexpected electron accumulation on nonpolar {010} facets in wurtzite ZnO platelets (N‐ZnO), which represents a dynamic “electron spillover” process beyond static facet confinement. Crucially, femtosecond transient absorption (fs‐TA) spectroscopy directly captures interfacial electron transfer from polar Zn‐terminated (0001) facets (Zn‐ZnO) to N‐ZnO with a lifetime of 60.82 ps. However, electrons spilling over from Zn‐ZnO to N‐ZnO recombine with the photogenerated holes inherent to N‐ZnO, thereby turning it into a recombination center. Guided by this insight, we construct a dual‐cocatalyst architecture (AuZnOCo): Au is selectively anchored on N‐ZnO and Zn‐ZnO to extract electrons, and Co ₃ O ₄ is deposited on O‐terminated (000) facets (O‐ZnO) to trap holes. The loading of dual cocatalysts promotes charge separation and suppresses this electron spillover‑induced recombination. Quantitative analysis reveals ≈3739 holes localized on O‐ZnO, ≈1771 electrons on Zn‐ZnO, and ≈812 electrons on N‐ZnO in AuZnOCo, while the electron diffusion length ( L ) increases from 81.41 to 121.77 nm. This work deciphers the spatiotemporal resolution of charge‐carrier dynamics, offering a blueprint for rationally engineering anisotropic photocatalysts.

Hydrogen peroxide (H ₂ O ₂ ) is an essential green oxidant with broad industrial relevance. Photocatalytic oxygen reduction reaction (ORR) offers a sustainable method for producing oxygen, yet its efficiency is limited by poor charge separation and severe carrier recombination. Single‐component photocatalysts suffer from sluggish carrier dynamics, while multi‐energy‐state systems frequently experience recombination at intermediate states. S‐scheme heterojunction engineering offers an effective strategy to address these challenges by regulating interfacial charge transfer while preserving strong redox potentials. Here, we report the construction of an S‐scheme photocatalyst by integrating a triazine‐based covalent organic framework (COF) with sulfur‐vacancy‐rich Mn _0.2 Cd _0.8 S (Sv‐MCS). This dual‐functional design preserves both the intrinsic n→π* electronic transitions of the COF and defect‐state absorption of Sv‐MCS, delivering an exceptional H ₂ O ₂ production rate of 5389.6 µmol·h ⁻¹ ·g ⁻¹ in pure water. Concurrently, the photostability of the catalyst is simultaneously enhanced. X‐ray absorption fine‐structural analysis confirms interfacial Cd–O coordination between Cd atoms and COF carbonyl groups. In situ spectroscopies combined with density functional theory elucidate a preferential two‐electron ORR pathway, while femtosecond transient absorption spectroscopy confirms suppressed carrier recombination enabled by synergistic S‐scheme charge transfer and interfacial chemical bonding. This work establishes design principles for multi‐energy‐state S‐scheme photocatalysts and advances solar‐driven H ₂ O ₂ production toward artificial photosynthesis.

Solar-driven catalytic technologies offer alternative pathways for addressing global challenges in energy sustainability and environmental remediation. Photocatalysis and photoelectrocatalysis have received considerable attention for their potential to convert abundant solar energy into chemical fuels and value-added products. Despite remarkable progress over the past decades, the practical implementation of these technologies still faces major challenges, including limited light utilization, rapid charge recombination, and an insufficiently explored understanding of reaction mechanisms. This Editorial briefly summarizes the current state of the art in photocatalysis and highlights future research directions with a focus on advanced material design and mechanistic investigations.

Rational engineering of photocatalysts with spatially separated photophysical and catalytic functions is an effective strategy to alleviate charge recombination and kinetic bottlenecks in solar hydrogen evolution. Herein, we developed a family of atomically engineered metal–organic frameworks (MOFs)‐based photocatalysts, denoted as 125‐TNQ‐M (M = Co, Ni, Cu), constructed by Schiff‐base modification of NH ₂ ‐MIL‐125(Ti) with thionaphthenquinone (TNQ), followed by covalent anchoring of Lewis‐acidic single metal atoms onto its framework. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM), synchrotron‐based x‐ray absorption spectroscopy (XAS), and x‐ray photoelectron spectroscopy (XPS) analyses confirm the atomic dispersion of M sites and reveal their unique coordination environments. Among them, 125‐TNQ‐Ni demonstrates the highest hydrogen evolution rate of 13.54 mmol g ⁻¹ h ⁻¹ under visible‐light irradiation, far surpassing pristine MOFs. Mechanistic studies combining electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations reveal that Ni single atoms function as efficient electron extraction and proton‐reduction centers, while the Ti‐oxo clusters act as photoactive charge‐generation units. The enhanced activity originates from metal‐induced reorganization of the hydrogen evolution pathway and improved charge separation, rather than direct dual‐metal synergy. This work establishes a structurally well‐defined MOF‐based platform for decoupling light harvesting and catalytic functions at the atomic scale.

Rational engineering of photocatalysts with spatially separated photophysical and catalytic functions is an effective strategy to alleviate charge recombination and kinetic bottlenecks in solar hydrogen evolution. Herein, we developed a family of atomically engineered metal–organic frameworks (MOFs)‐based photocatalysts, denoted as 125‐TNQ‐M (M = Co, Ni, Cu), constructed by Schiff‐base modification of NH ₂ ‐MIL‐125(Ti) with thionaphthenquinone (TNQ), followed by covalent anchoring of Lewis‐acidic single metal atoms onto its framework. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM), synchrotron‐based x‐ray absorption spectroscopy (XAS), and x‐ray photoelectron spectroscopy (XPS) analyses confirm the atomic dispersion of M sites and reveal their unique coordination environments. Among them, 125‐TNQ‐Ni demonstrates the highest hydrogen evolution rate of 13.54 mmol g ⁻¹ h ⁻¹ under visible‐light irradiation, far surpassing pristine MOFs. Mechanistic studies combining electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations reveal that Ni single atoms function as efficient electron extraction and proton‐reduction centers, while the Ti‐oxo clusters act as photoactive charge‐generation units. The enhanced activity originates from metal‐induced reorganization of the hydrogen evolution pathway and improved charge separation, rather than direct dual‐metal synergy. This work establishes a structurally well‐defined MOF‐based platform for decoupling light harvesting and catalytic functions at the atomic scale.

ConspectusA persistent obstacle in heterogeneous photocatalysis is the rapid recombination of photogenerated electrons and holes, a consequence of the strong Coulombic attraction between carriers within conventional semiconductors. This intrinsic limitation significantly constrains the efficiency of solar-to-chemical conversion processes. Heterojunction engineering has therefore become a central strategy for promoting charge separation by coupling semiconductors with complementary electronic structures. Such systems typically outperform their single-component analogues because the interfacial electronic configuration promotes directional charge migration and suppresses bulk recombination losses.Within this context, S-scheme heterojunctions (SH) offer a mechanistically robust framework that reconciles efficient carrier separation with strong redox capability. An S-scheme couples a reduction photocatalyst (RP) and an oxidation photocatalyst (OP) in a staggered configuration. Under illumination, electrons in the OP selectively recombine with holes in the RP, while the high-energy electrons in the RP and high-energy holes in the OP are spatially retained and directed to catalytic sites. This selective recombination preserves redox power, enhances charge utilization, and accelerates surface reactions.Since introducing the S-scheme concept in 2019 with the WO₃/g-C₃N₄ system supported by in situ irradiated X-ray photoelectron spectroscopy (ISIXPS)─we have expanded its material scope across multiple dimensional architectures, including perovskite materials, semiconducting quantum dots (QDs), conjugated polymers (CP), metal-organic frameworks (MOFs), and covalent-organic frameworks (COFs). To validate the S-scheme mechanism, elucidate charge transfer dynamics, and resolve reaction mechanisms, we have employed an array of state-of-the-art characterization techniques, such as light-irradiated Kelvin probe force microscopy (KPFM), in situ electron paramagnetic resonance (EPR), in situ X-ray absorption spectroscopy (XAS), and femtosecond-transient absorption spectroscopy (fs-TAS).Our most recent efforts focus on composition tuning, defect modulation, and interfacial bonding engineering to optimize the separation and lifetime of photogenerated carriers. Through these strategies, we aim to reinforce the internal electric field, regulate band bending, and precisely control charge flow pathways, ultimately maximizing photocatalytic efficiency. This Account provides a concise yet comprehensive overview of the evolution of SH, with emphasis on the design principles and advanced characterization techniques developed and adopted by our group. We summarize key strategies for engineering SH tailored for enhanced charge carrier separation and highlight their applications in major photocatalytic reactions. Finally, we outline promising future directions for the field.

The efficient utilization of solar energy to convert carbon dioxide into renewable fuels is a compelling strategy for mitigating carbon emissions and realizing sustainable chemical cycles. Herein, we report a Ni–modified oxygen–deficient TiO ₂ (Ni/TiO _2‐x ) catalyst that achieves exceptionally high photothermal CO ₂ reduction performance under simulated solar irradiation without external heating, reaching a remarkable total production yield of 278.3 mmol·g ⁻¹ ·h ⁻¹ . Structural and spectroscopic analyses reveal that the asymmetric Ni–V _O –Ti interfacial configuration serves as a unique charge polarization center that redistributes charge density and stabilizes reaction intermediates under light–induced thermal excitation. This asymmetric coordination disrupts the electronic degeneracy of the Ti─O framework, thereby lowering the free energy barrier for the rate–determining step. Density functional theory (DFT) calculations further demonstrate that the asymmetric site acts as a dual–function photothermal antenna, where light absorption and heat localization cooperate to accelerate H ₂ activation and C─O bond cleavage. This work unveils a paradigm in which geometric asymmetry governs both charge transfer and localized heat management, providing a molecular–level blueprint for next–generation photothermal catalysts for solar–driven CO ₂ conversion.