From UV to Near-Infrared Light-Responsive Metal-Organic Framework Composites: Plasmon and Upconversion Enhanced Photocatalysis

Near-infrared light-induced homogeneous photoelectrochemical biosensor based on 3D walking nanomotor-assisted CRISPR/Cas12a for ultrasensitive microRNA-155 detection

The dysregulation of microRNA (miRNA) expression levels is intricately linked to a myriad of human diseases, and the precise and delicate detection thereof holds paramount significance in the realm of clinical diagnosis and therapy. Herein, a near-infrared (NIR) light-mediated homogeneous photoelectrochemical (PEC) biosensor was constructed for miRNA-155 detection based on NaYF4: Yb, Tm@ZnIn2S4 (NYF@ ZIS) coupled with a three-dimensional (3D) walking nanomotor-assisted CRISPR/Cas12a strategy. The upconverted light emitted by the NYF in the visible and UV region upon NIR light excitation could be utilized to excite ZIS to produce a photocurrent response. The presence of target miRNA-155 initiated an amplification reaction within the 3D walking nanomotor, resulting in the production of multiple nucleic acid fragments. These fragments could activate the collateral cleavage capability of CRISPR/Cas12a, leading to the indiscriminate cleavage of single-stranded DNA (ssDNA) on ALP-ssDNA-modified magnetic beads and the subsequent liberation of alkaline phosphatase (ALP). The released ALP facilitated the catalysis of ascorbic acid 2-phosphate to generate ascorbic acid as the electron donor to capture the photogenerated holes on the NYF@ZIS surface, resulting in a positively correlated alteration in the photocurrent response. Under optimal conditions, the NIR light-initiated homogeneous PEC biosensor had the merits of good linear range (0.1 fM to 100 pM), an acceptable limit of detection (65.77 aM) for miRNA-155 detection. Considering the pronounced sensitivity, light stability, and low photodamage, this strategy presents a promising platform for detecting various other miRNA biomarkers in molecular diagnostic practice.

Water-Stable High-Entropy Metal-Organic Framework Nanosheets for Photocatalytic Hydrogen Production

Metal-organic frameworks (MOFs) have emerged as promising platforms for photocatalytic hydrogen evolution reaction (HER) due to their fascinating physiochemical properties. Rationally engineering the compositions and structures of MOFs can provide abundant opportunities for their optimization. In recent years, high-entropy materials (HEMs) have demonstrated great potential in the energy and environment fields. However, there is still no report on the development of high-entropy MOFs (HE-MOFs) for photocatalytic HER in aqueous solution. Herein, the authors report the synthesis of a novel p-type HE-MOFs single crystal (HE-MOF-SC) and the corresponding HE-MOFs nanosheets (HE-MOF-NS) capable of realizing visible-light-driven photocatalytic HER. Both HE-MOF-SC and HE-MOF-NS exhibit higher photocatalytic HER activity than all the single-metal MOFs, which are supposed to be ascribed to the interplay between the different metal nodes in the HE-MOFs that enables more efficient charge transfer. Moreover, impressively, the HE-MOF-NS demonstrates much higher photocatalytic activity than the HE-MOF-SC due to its thin thickness and enhanced surface area. At optimum conditions, the rate of H2 evolution on the HE-MOF-NS is ≈13.24 mmol h-1 g-1, which is among the highest values reported for water-stable MOF photocatalysts. This work highlights the importance of developing advanced high-entropy materials toward enhanced photocatalysis.

Enhanced photocatalysis of metal/covalent organic frameworks by plasmonic nanoparticles and homo/hetero-junctions

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have garnered attention in photocatalysis due to their unique features including extensive surface area, adjustable pores, and the ability to incorporate various functional groups. However, challenges such as limited visible light absorption and rapid electron-hole recombination often hinder their photocatalytic efficiency. Recent developments have introduced plasmonic nanoparticles (NPs) and junctions to enhance the photocatalytic performance of MOFs/COFs. This paper provides a comprehensive review of recent advancements in MOF/COF-based photocatalysts improved by integration of plasmonic NPs and junctions. We begin by examining the utilization of plasmonic NPs, known for absorbing longer-wavelength light compared to typical MOFs/COFs. These NPs exhibit localized surface plasmon resonance (LSPR) when excited, effectively enhancing the photocatalytic performance of MOFs/COFs. Moreover, we discuss the role of homo/hetero-junctions in facilitating charge separation, further boosting the photocatalytic performance of MOFs/COFs. The mechanisms behind the improved photocatalytic performance of these composites are discussed, along with an assessment of challenges and opportunities in the field, guiding future research directions.

Manipulation of interfacial charge dynamics for metal-organic frameworks toward advanced photocatalytic applications

Compared to other known materials, metal-organic frameworks (MOFs) have the highest surface area and the lowest densities; as a result, MOFs are advantageous in numerous technological applications, especially in the area of photocatalysis. Photocatalysis shows tantalizing potential to fulfill global energy demands, reduce greenhouse effects, and resolve environmental contamination problems. To exploit highly active photocatalysts, it is important to determine the fate of photoexcited charge carriers and identify the most decisive charge transfer pathway. Methods to modulate charge dynamics and manipulate carrier behaviors may pave a new avenue for the intelligent design of MOF-based photocatalysts for widespread applications. By summarizing the recent developments in the modulation of interfacial charge dynamics for MOF-based photocatalysts, this minireview can deliver inspiring insights to help researchers harness the merits of MOFs and create versatile photocatalytic systems.

Full-Spectrum Utilization of ZIF-67/Ag NPs/NaYF4 :Yb,Er Photocatalysts for Efficient Degradation of Sulfadiazine: Upconversion Mechanism and DFT Calculation

In this work, novel ternary composite ZIF-67/Ag NPs/NaYF4 :Yb,Er is synthesized by solvothermal method. The photocatalytic activity of the composite is evaluated by sulfadiazine (SDZ) degradation under simulated sunlight. High elimination efficiency of the composite is 95.4% in 180 min with good reusability and stability. The active species (h+ , ·O2 - and ·OH) are identified. The attack sites and degradation process of SDZ are deeply investigated based on theoretical calculation and liquid chromatography-mass spectrometry analysis. The upconversion mechanism study shows that favorable photocatalytic effectiveness is attributed to the full utilization of sunlight through the energy transfer upconversion process and fluorescence resonance energy transfer. Additionally, the composite is endowed with outstanding light-absorbing qualities and effective photogenerated electron-hole pair separation thanks to the localized surface plasmon resonance effect of Ag nanoparticles. This work can motivate further design of novel photocatalysts with upconversion luminescence performance, which are applied to the removal of sulphonamide antibiotics in the environment.

Photoswitchable Radical State in Nanoporous Metal-Organic Framework Films with Embedded Hexaarylbiimidazole

Photoresponsive materials enable dynamic remote control of their fundamental properties. The incorporation of photochromic molecules in nanoporous metal-organic frameworks (MOFs) provides a unique opportunity to tailor the material properties, including the interaction between the MOF host and guest molecules in the pores. Here, a MOF film of type HKUST-1 with embedded hexaarylbiimidazole (HABI), undergoing reversible light-induced reactions between the stable dimer state and the metastable radical state, is presented. The switching between the dimer and radical form is shown by infrared, UV-vis, and electron paramagnetic resonance (EPR) spectroscopy. By transient uptake experiments with ethanol and methanol as probe molecules, we show that the dimer-radical switching impacts the host-guest interaction and, in particular, modifies the uptake amount and diffusion coefficient of the guest molecules. For ethanol, the diffusion slows down by 75%. This research presents the first MOF material with photoswitchable (meta)stable dimer and radical molecules, and it contributes to the advancement of photoresponsive nanoporous materials.

UV-to-NIR Harvesting Conjugated Porous Polymer Nanocomposite: Upconversion and Plasmon Expedited Thioether Photooxidation

Photocatalysts capable of harvesting a broad range of the solar spectrum are essential for sustainable chemical transformations and environmental remediation. Herein, we have integrated NIR-absorbing upconversion nanoparticles (UCNP) with UV-Vis absorbing conjugated porous organic polymer (POP) through the in situ multicomponent C-C coupling to fabricate a UC-POP nanocomposite. The light-harvesting ability of UC-POP is further augmented by loading plasmonic gold nanoparticles (AuNP) into UC-POP. A three-times enhancement in the upconversion luminescence is observed upon the incorporation of AuNP in UC-POP, subsequently boosting the photocatalytic activity of UC-POP-Au. The spectroscopic and photoelectrochemical investigations infer the enhanced photocatalytic oxidation of thioethers, including mustard gas simulant by UC-POP-Au compared to POP and UC-POP due to the facile electron-hole pair generation, suppressed exciton recombination, and efficient charge carrier migration. Thus, the unique design strategy of combining plasmonic and upconversion nanoparticles with a conjugated porous organic polymer opens up new vistas towards artificial light harvesting.

Conductive Polymer-Inorganic Polythiophene/Cd0.5Zn0.5S Heterojunction with Apace Charge Separation and Strong Light Absorption for Boosting Photocatalytic Activity

In order to utilize the synergistic effect between a conductive polymer and an inorganic semiconductor to efficaciously enhance charge transfer and solve the problem of unsatisfactory performance of a single photocatalyst, thiophene (Th) was polymerized on the Cd0.5Zn0.5S nanoparticle surface to prepare a conductive polymer-inorganic polythiophene/Cd0.5Zn0.5S (PTh/CZS) heterostructrue through a simple in situ oxidation polymerization for the first time. The as-prepared PTh/CZS heterostructures significantly improved photocatalytic TCH degradation and hydrogen production activities. Especially, the 15PTh/CZS sample exhibited the optimal hydrogen production rate (18.45 mmol g-1 h-1), which was 2.51 times higher than pure Cd0.5Zn0.5S nanoparticles. In addition, 15PTh/CZS also showed very fast and efficient photodegradation ability for degrading 88% of TCH in 25 min. Moreover, the degradation rate (0.06229 min-1) was five times more than that of Cd0.5Zn0.5S. The π-π* transition characteristics, high optical absorption coefficient, wide absorption wavelength of PTh, the tight contact interface, and synergistic effect of PTh and Cd0.5Zn0.5S efficiently boosted charge transfer rate and increased the light absorption of PTh/CZS photocatalysts, which greatly enhanced the photocatalytic abilities. Besides, the mechanism of improved photocatalytic activities for TCH degradation and H2 production was also carefully proposed. Undoubtedly, this work would provide new insights into coupling conductive polymers to inorganic photocatalysts for achieving multifunctional applications in the field of photocatalysis.

Size- and Emission-Controlled Synthesis of Full-Color Luminescent Metal-Organic Frameworks for Tryptophan Detection

The development of nanoscaled luminescent metal-organic frameworks (nano-LMOFs) with organic linker-based emission to explore their applications in sensing, bioimaging and photocatalysis is of great interest as material size and emission wavelength both have remarkable influence on their performances. However, there is lack of platforms that can systematically tune the emission and size of nano-LMOFs with customized linker design. Herein two series of fcu- and csq-type nano-LMOFs, with precise size control in a broad range and emission colors from blue to near-infrared, were prepared using 2,1,3-benzothiadiazole and its derivative based ditopic- and tetratopic carboxylic acids as the emission sources. The modification of tetratopic carboxylic acids using OH and NH2 as the substituent groups not only induces significant emission bathochromic shift of the resultant MOFs, but also endows interesting features for their potential applications. As one example, we show that the non-substituted and NH2 -substituted nano-LMOFs exhibit turn-off and turn-on responses for highly selective and sensitive detection of tryptophan over other nineteen natural amino acids. This work sheds light on the rational construction of nano-LMOFs with specific emission behaviours and sizes, which will undoubtedly facilitate their applications in related areas.

Near-infrared metal agents assisting precision medicine: from strategic design to bioimaging and therapeutic applications

Metal agents have made incredible strides in preclinical research and clinical applications in recent years, but their short emission/absorption wavelengths continue to be a barrier to their distribution, therapeutic action, visual tracking, and efficacy evaluation. Nowadays, the near-infrared window (NIR, 650-1700 nm) provides a more accurate imaging and treatment option. Thus, there has been ongoing research focusing on developing multifunctional NIR metal agents for imaging and therapy that have deeper tissue penetration. The design, characteristics, bioimaging, and therapy of NIR metal agents are covered in this overview of papers and reports published to date. To start with, we focus on describing the structure, design strategies, and photophysical properties of metal agents from the NIR-I (650-1000 nm) to NIR-II (1000-1700 nm) region, in order of molecular metal complexes (MMCs), metal-organic complexes (MOCs), and metal-organic frameworks (MOFs). Next, the biomedical applications brought by these superior photophysical and chemical properties for more accurate imaging and therapy are discussed. Finally, we explore the challenges and prospects of each type of NIR metal agent for future biomedical research and clinical translation.

Construction of graphene quantum dots ratiometric fluorescent probe by intermolecular electron transfer effect for intelligent and real-time visual detection of ofloxacin and its L-isomer in daily drink

The design of intelligent and real-time sensing devices is significant in the medical drug monitoring field, but it is still highly challenging. Here, ratiometric fluorescent detections of ofloxacin (OFL) and its L-isomer levofloxacin (LEV) constructed from tri-doped graphene quantum dots (T-GQDs) are reported, and the detection limits reach as low as 46/67 nM toward OFL/LEV due to the intermolecular electron transfer (intermolecular ET) effect. After adding OFL/LEV, the generation of electrostatic bond provides a channel for the intermolecular ET from the edge of T-GQDs to OFL/LEV, resulting in the fluorescence quenching at 414 nm and the fluorescence promoting at 498 nm. Furthermore, a smartphone can be used for the visual and quantitative detection of OFL and LEV by identifying the RGB values of test paper and drink samples. This work not only reveals the physics mechanism of ratiometric detection, but also develops a convenient smartphone diagnostic for OFL and LEV.

Zr- and Ti-based metal-organic frameworks: synthesis, structures and catalytic applications

Recently, Zr- and Ti-based metal-organic frameworks (MOFs) have gathered increasing interest in the field of chemistry and materials science, not only for their ordered porous structure, large surface area, and high thermal and chemical stability, but also for their various potential applications. Particularly, the unique features of Zr- and Ti-based MOFs enable them to be a highly versatile platform for catalysis. Although much effort has been devoted to developing Zr- and Ti-based MOF materials, they still suffer from difficulties in targeted synthesis, especially for Ti-based MOFs. In this Feature Article, we discuss the evolution of Zr- and Ti-based MOFs, giving a brief overview of their synthesis and structures. Furthermore, the catalytic uses of Zr- and Ti-based MOF materials in the previous 3-5 years have been highlighted. Finally, perspectives on the Zr- and Ti-based MOF materials are also proposed. This work provides in-depth insight into the advances in Zr- and Ti-based MOFs and boosts their catalytic applications.

An NIR-Driven Upconversion/C3N4/CoP Photocatalyst for Efficient Hydrogen Production by Inhibiting Electron-Hole Pair Recombination for Alzheimer's Disease Therapy

Redox imbalance and abnormal amyloid protein (Aβ) buildup are key factors in the etiology of Alzheimer's disease (AD). As an antioxidant, the hydrogen molecule (H₂) has the potential to cure AD by specifically scavenging highly harmful reactive oxygen species (ROS) such as ^•OH. However, due to the low solubility of H₂ (1.6 ppm), the traditional H₂ administration pathway cannot easily achieve long-term and effective accumulation of H₂ in the foci. Therefore, how to achieve the continuous release of H₂ in situ is the key to improve the therapeutic effect on AD. As a corollary, we designed a rare earth ion doped g-C₃N₄ upconversion photocatalyst, which can respond to NIR and realize the continuous production of H₂ by photocatalytic decomposition of H₂O in biological tissue, which avoids the problem of the poor penetration of visible light. The introduction of CoP cocatalyst accelerates the separation and transfer of photogenerated electrons in g-C₃N₄, thus improving the photocatalytic activity of hydrogen evolution reaction. The morphology of the composite photocatalyst was shown by transmission electron microscopy, and the crystal structure was studied by X-ray diffractometry and Raman analysis. In addition, the ability of g-C₃N₄ to chelate metal ions and the photothermal properties of CoP can inhibit Aβ and reduce the deposition of Aβ in the brain. Efficient in situ hydrogen production therapy combined with multitarget synergism solves the problem of a poor therapeutic effect of a single target. In vivo studies have shown that UCNP@CoP@g-C₃N₄ can reduce Aβ deposition, improve memory impairment, and reduce neuroinflammation in AD mice.

Exploiting the LSPR effect for an enhanced photocatalytic hydrogen evolution reaction

Incorporation of plasmonic metals is one of the most widely adopted strategies for improving the photocatalytic hydrogen evolution reaction (HER) activity of semiconductor photocatalysts. This article summarizes recent advances in the development of plasmonic metal-semiconductor photocatalysts and four localized surface plasmon resonance (LSPR) driven mechanisms by which plasmonic metal nanoparticles can contribute to enhancement of HER activity. In addition, principles for maximizing the contribution of these LSPR driven mechanisms are highlighted to provide insights for future design of plasmonic metal-semiconductor photocatalysts with enhanced HER activity.

Molecular-level Manipulation of Interface Charge Transfer on Plasmonic Metal/MOF Heterostructures

Plasmon-excited hot carriers have drawn great attention for driving various chemical reactions, but the short lifetimes of hot carriers seriously restrict the performance of plasmonic photocatalysis. Constructing plasmonic metal/metal-organic framework (MOF) heterostructures has been proved as an effective strategy to extend the lifetimes of hot carriers. Due to the high molecular tunability of MOFs, the MOF substrate in plasmonic metal/MOF heterostructures is able to capture hot electrons on the conduction band of MOF and hot holes on its valence band, and thus offers an ideal platform to separately study the detailed mechanism of hot electron and hole transfer processes. This review focuses on a molecular-level understanding of both hot-electron and hot-hole transfer at plasmonic metal/MOF interfaces. The enhanced stability and photocatalytic performance by introducing MOF substrates are discussed for plasmonic metal/MOF heterostructures. Additionally, typical characterization technologies are also proposed as powerful tools for tracking hot carrier transfer process.

In-depth insight into the Yb3+ effect in NaErF4-based host sensitization upconversion: a double-edged sword

NaErF₄ is the most extensively studied host for self-sensitized upconversion (UC), and Yb³⁺ is the most commonly used energy absorber. It has been reported that the red luminescence of Er³⁺ can be enhanced by introducing Yb³⁺ into the NaErF₄ host lattice, where Yb³⁺ ions serve as trapping centers to confine the excitation energy. Also, it has been pointed out that the Yb³⁺ doping in the shell of NaErF₄-hosted core-shell nanocrystals can further improve the red emission intensity. Conversely, it can be argued that the Yb³⁺ doping in the shell always results in the luminescence quenching of the NaErF₄ core. These imply that the impact of Yb³⁺ on NaErF₄-based host-sensitized UC is rather complicated and must be probed deeply. In this study, we thoroughly discussed the effect of Yb³⁺ located in the core/shell on the NaErF₄-based host sensitization UC and afforded the related mechanism interpretations. In the NaErF₄ core nanocrystals, the green-dominated UCL presented an enhancement on increasing the concentration of the Yb³⁺ dopant owing to the promoted energy harvesting for luminescence. Furthermore, the emission properties of NaErF₄:10%Yb shelled with diverse inert layers were also investigated, and the intensity difference of these core-inert shell nanoparticles could be explained by the lattice mismatch and shell thickness. In NaErF₄:10%Yb@NaYF₄:Yb with variable Yb³⁺ doping in the shell, the red-dominated UCL was generally weakened with more Yb³⁺ localized in the shell, which was ascribed to the competition of energy pooling and energy dissipation of Yb³⁺ in the outer layer. Therefore, Yb³⁺ ions wield a two-sided influence (termed a "double-edged sword") on the UC emissions of the Er³⁺ host. Additionally, we demonstrated the application potential of such UCNPs in water sensing and high-level anti-counterfeiting. This work offers an in-depth insight into the UC mechanism of Yb³⁺-doped NaErF₄ nanocrystals and inspires the engineering of novel luminescent materials with distinguished properties.

Metal-Organic Frameworks Meet Molecularly Imprinted Polymers: Insights and Prospects for Sensor Applications

The use of porous materials as the core for synthesizing molecularly imprinted polymers (MIPs) adds significant value to the resulting sensing system. This review covers in detail the current progress and achievements regarding the synergistic combination of MIPs and porous materials, namely metal/covalent-organic frameworks (MOFs/COFs), including the application of such frameworks in the development of upgraded sensor platforms. The different processes involved in the synthesis of MOF/COF-MIPs are outlined, along with their intrinsic properties. Special attention is paid to debriefing the impact of the morphological changes that occur through the synergistic combination compared to those that occur due to the individual entities. Thereafter, the strategies used for building the sensors, as well as the transduction modes, are overviewed and discussed. This is followed by a full description of research advances for various types of MOF/COF-MIP-based (bio)sensors and their applications in the fields of environmental monitoring, food safety, and pharmaceutical analysis. Finally, the challenges/drawbacks, as well as the prospects of this research field, are discussed in detail.

Recent Development in Sensitizers for Lanthanide-Doped Upconversion Luminescence

The attractive features of lanthanide-doped upconversion luminescence (UCL), such as high photostability, nonphotobleaching or photoblinking, and large anti-Stokes shift, have shown great potentials in life science, information technology, and energy materials. Therefore, UCL modulation is highly demanded toward expected emission wavelength, lifetime, and relative intensity in order to satisfy stringent requirements raised from a wide variety of areas. Unfortunately, the majority of efforts have been devoted to either simple codoping of multiple activators or variation of hosts, while very little attention has been paid to the critical role that sensitizers have been playing. In fact, different sensitizers possess different excitation wavelengths and different energy transfer pathways (to different activators), which will lead to different UCL features. Thus, rational design of sensitizers shall provide extra opportunities for UCL tuning, particularly from the excitation side. In this review, we specifically focus on advances in sensitizers, including the current status, working mechanisms, design principles, as well as future challenges and endeavor directions.

Efficient Reduction Photocatalyst of 4-Nitrophenol Based on Ag-Nanoparticles-Doped Porous ZnO Heterostructure

Oxide-supported Ag nanoparticles have been widely reported as a good approach to improve the stability and reduce the cost of photocatalysts. In this work, a Ag-nanoparticles-doped porous ZnO photocatalyst was prepared by using metal-organic frameworks as a sacrificial precursor and the catalytic activity over 4-nitrophenol was determined. The Ag-nanoparticles-doped porous ZnO heterostructure was evaluated by UV, XRD, and FETEM, and the catalytic rate constant was calculated by the change in absorbance value at 400 nm of 4-nitrophenol. The photocatalyst with a heterogeneous structure is visible, light-responsive, and beneficial to accelerating the catalytic rate. Under visible light irradiation, the heterostructure showed excellent catalytic activity over 4-nitrophenol due to the hot electrons induced by the localized surface plasmon resonance of Ag nanoparticles. Additionally, the catalytic rates of 4 nm/30 nm Ag nanoparticles and porous/nonporous ZnO were compared. We found that the as-prepared Ag-nanoparticles-doped porous ZnO heterostructure catalyst showed enhanced catalytic performance due to the synergetic effect of Ag nanoparticles and porous ZnO. This study provides a novel heterostructure photocatalyst with potential applications in solar energy and pollutant disposal.

Solar Energy Catalysis

When it comes to using solar energy to promote catalytic reactions, photocatalysis technology is the first choice. However, sunlight can not only be directly converted into chemical energy through a photocatalytic process, it can also be converted through different energy-transfer pathways. Using sunlight as the energy source, photocatalytic reactions can proceed independently, and can also be coupled with other catalytic technologies to enhance the overall catalytic efficiency. Therefore, sunlight-driven catalytic reactions are diverse, and need to be given a specific definition. We propose a timely perspective for catalytic reactions driven by sunlight and give them a specific definition, namely "solar energy catalysis". The concept of different types of solar energy catalysis, such as photocatalysis, photothermal catalysis, solar cell powered electrocatalysis, and pyroelectric catalysis, are highlighted. Finally, their limitations and future research directions are discussed.

Nanocomposites based on lanthanide-doped upconversion nanoparticles: diverse designs and applications

Lanthanide-doped upconversion nanoparticles (UCNPs) have aroused extraordinary interest due to the unique physical and chemical properties. Combining UCNPs with other functional materials to construct nanocomposites and achieve synergistic effect abound recently, and the resulting nanocomposites have shown great potentials in various fields based on the specific design and components. This review presents a summary of diverse designs and synthesis strategies of UCNPs-based nanocomposites, including self-assembly, in-situ growth and epitaxial growth, as well as the emerging applications in bioimaging, cancer treatments, anti-counterfeiting, and photocatalytic fields. We then discuss the challenges, opportunities, and development tendency for developing UCNPs-based nanocomposites.

Modifying SnS2 With Carbon Quantum Dots to Improve Photocatalytic Performance for Cr(VI) Reduction

The photoreduction for hazardous Cr(VI) in industrial wastewater has been considered a "green" approach with low-cost and easy-to-go operation. SnS₂ is a promising narrow bandgap photocatalyst, but its low charge carrier separation efficiency should be solved first. In this work, N-doped carbon quantum dots (CQDs) were prepared and loaded onto SnS₂ nanoparticles via an in situ method. The resulting composite samples (NC@SnS₂) were characterized, and their photocatalytic performance was discussed. SnS₂ nanoparticles were obtained as hexagonal ones with a bandgap of 2.19 eV. The optimal doping level for NC@SnS₂ was citric acid: urea:SnS₂ = 1.2 mmol:1.8 mmol:3.0 mmol. It showed an average diameter of 40 nm and improved photocatalytic performance, compared to pure SnS₂, following a pseudo-first-order reaction with a kinetic rate constant of 0.1144 min^-1. Over 97% of Cr(VI) was photo-reduced after 30 min. It was confirmed that modification of SnS₂ with CQDs can not only improve the light-harvesting ability but also stimulate the charge separation, which therefore can enhance the photoreactivity of SnS₂ toward Cr(VI) reduction. The excellent stability of NC@SnS₂ indicates that it is promising to be practically used in industrial wastewater purification.

Electron Donor-Acceptor Interface of TPPS/PDI Boosting Charge Transfer for Efficient Photocatalytic Hydrogen Evolution

Charge separation efficiency of photocatalysts is still the key scientific issue for solar-to-chemical energy conversion. In this work, an electron donor-acceptor (D-A) interface with high charge separation between TPPS (tetra(4-sulfonatophenyl)porphyrin) and PDI (perylene diimide) is successfully constructed for boosting photocatalytic H₂ evolution. The TPPS/PDI with D-A interface shows excellent photocatalytic H₂ evolution rate of 546.54 µmol h^-1 (30.36 mmol h^-1 g^-1 ), which is 9.95 and 9.41 times higher than that of pure TPPS and PDI, respectively. The TPPS/PDI has a markedly stronger internal electric field, which is respectively 3.76 and 3.01 times higher than that of pure PDI and TPPS. The D-A interface with giant internal electric field efficiently facilitates charge separation and urges TPPS/PDI to have a longer excited state lifetime than single component. The work provides entirely new ideas for designing materials with D-A interface to realize high photocatalytic activity.

Enhancement of solar-driven photocatalytic activity of oxygen vacancy-rich Bi/BiOBr/Sr2LaF7:Yb3+,Er3+ composites through synergetic strategy of upconversion function and plasmonic effect

For better use of solar energy, the development of efficient broadband photocatalyst has attracted extraordinary attention. In this study, a ternary composite consisting of Sr₂LaF₇:Yb³⁺,Er³⁺ upconversion (UC) nanocrystals and Bi nanoparticles loaded BiOBr nanosheets with oxygen vacancies (OVs, SLFBB) was designed and synthesized by multistep solvent-thermal method. Mechanisms of in-situ formation of Bi nanoparticles and OVs in BiOBr/Sr₂LaF₇:Yb³⁺,Er³⁺ composites (SFLB) are clarified. The Bi metal and OVs enhanced the light-harvesting capacity in the region of visible-near-infrared (Vis-NIR), and promoted the separation of electron-hole (e^-/h⁺) pairs. Furthermore, the surface plasmon resonance (SPR) effect of Bi metal can improve the energy transfer from Sr₂LaF₇:Yb³⁺,Er³⁺ to BiOBr via nonradiative energy transfer process, resulting in enhancing the light utilization from upconverting NIR into Vis light. Due to the synergistic effects of UC function, SPR and OVs, the SFLBB exhibited obviously enhanced photocatalytic ability for the degradation of BPA with a rate of 8.9 × 10^-3 min^-1, which is about 2.78 times higher than 3.2 × 10^-3 min^-1 of BiOBr (BOB) under UV-Vis-NIR light irradiation. This work provides a novel strategy for the project of high-efficiency Bismuth-based broadband photocatalysts, which is helpful to further understand the mechanism of enhanced photocatalysis by UC function and plasmonic effect.

Upconversion nanoparticles coupled with hierarchical ZnIn2S4 nanorods as a near-infrared responsive photocatalyst for photocatalytic CO2 reduction

Developing near-infrared responsive (NIR) photocatalysts is very important for the development of solar-driven photocatalytic systems. Metal sulfide semiconductors have been extensively used as visible-light responsive photocatalysts for photocatalytic applications owing to their high chemical variety, narrow bandgap and suitable redox potentials, particularly the benchmark ZnIn₂S₄. However, their potential as NIR-responsive photocatalysts is yet to be reported. Herein, for the first time demonstrated that upconversion nanoparticles can be delicately coupled with hierarchical ZnIn₂S₄ nanorods (UCNPs/ZIS) to assemble a NIR-responsive composite photocatalyst, and as such composite is verified by ultraviolet-visible diffuse reflectance spectra and upconversion luminescence spectra. As a result, remarkable photocatalytic CO and CH₄ production rates of 1500 and 220 nmol g^-1h^-1, respectively, were detected for the UCNPs/ZIS composite under NIR-light irradiation (λ ≥ 800 nm), which is rarely reported in the literature. The remarkable photocatalytic activity of the UCNPs/ZIS composite can be understood not only because the heterojunction between UCNPs and ZIS can promote the charge separation efficiency, but also the intimate interaction of UCNPs with hierarchical ZIS nanorods can enhance the energy transfer. This finding may open a new avenue to develop more NIR-responsive photocatalysts for various solar energy conversion applications.

Direct Electron Transfer from Upconversion Graphene Quantum Dots to TiO2 Enabling Infrared Light-Driven Overall Water Splitting

Utilization of infrared light in photocatalytic water splitting is highly important yet challenging given its large proportion in sunlight. Although upconversion material may photogenerate electrons with sufficient energy, the electron transfer between upconversion material and semiconductor is inefficient limiting overall photocatalytic performance. In this work, a TiO₂/graphene quantum dot (GQD) hybrid system has been designed with intimate interface, which enables highly efficient transfer of photogenerated electrons from GQDs to TiO₂. The designed hybrid material with high photogenerated electron density displays photocatalytic activity under infrared light (20 mW cm⁻²) for overall water splitting (H₂: 60.4 μmol g_cat.⁻¹ h⁻¹ and O₂: 30.0 μmol g_cat.⁻¹ h⁻¹). With infrared light well harnessed, the system offers a solar-to-hydrogen (STH) efficiency of 0.80% in full solar spectrum. This work provides new insight into harnessing charge transfer between upconversion materials and semiconductor photocatalysts and opens a new avenue for designing photocatalysts toward working under infrared light.

Stable Zinc-Based Metal-Organic Framework Photocatalyst for Effective Visible-Light-Driven Hydrogen Production

Herein, a new Zn-MOF material, [Zn(L1)(L2)], 1, was built successfully through a one-pot solvothermal method. The 3D MOF structure was determined by Single X-ray diffraction analysis, IR, and elemental analysis. A series of PXRD tests of 1 after being immersed in different solvents and pH solutions demonstrated the good stability of 1. Interestingly, this material displayed high catalytic activity for the visible-light-driven hydrogen generation under the illumination of white LED in pure water or a mixture of DMF and H₂O without additional photosensitizers and cocatalysts. Besides, the studies also showed that the catalytic activity changed constantly as well as the solvent ratio adjustment of DMF and H₂O from 4:6 to 2:8. Additionally, the catalytic activity reached the best value (743 μmol g^-1 h^-1) when the solvent ratio was 4:6. The heterogeneous nature and recyclability of the MOF catalyst, as well as several factors that affect the catalytic activity, were investigated and described in detail. Moreover, the photocatalytic mechanism for the hydrogen generation of 1 was also proposed based on the fluorescence spectra and UV-vis absorption.

Efficient Electron Transfer by Plasmonic Silver in SrTiO3 for Low-Concentration Photocatalytic NO Oxidation

Photocatalysis presents a feasible option to control low-concentration NO emissions from industrial burning facilities, and increasing excitons in quantity and improving surface activity are the crucial issues to be solved. Plasmonic silver with the orientation of the (111) plane is uniformly distributed on the Ti-O termination of the SrTiO₃ (STO) (100) plane (major). The NO conversion rate has a sixfold increment compared to pristine STO. Meanwhile, the toxic NO₂ had a significant decline in the absence of water. This high performance could be attributed to the unique property of the localized surface plasmonic resonance of silver particles, which increases the optical response range of the catalyst. Meanwhile, the formation of a Schottky junction could promote the charge separation and enhance the lifetime of excitons via the electron transfer from silver particles to STO. More importantly, the Ag-O bond of the heterojunction increases the charge density of adjacent Ti, preferring to bond with the antibonding orbital electron of adsorbed molecules, which offers a favorable channel for the NO adsorption and activation of reactive oxidation species.

Diradical-Featured Organic Small-Molecule Photothermal Material with High-Spin State in Dimers for Ultra-Broadband Solar Energy Harvesting

Organic materials with radical characteristics are gaining increasing attention, due to their potential implications in highly efficient utilization of solar energy. Manipulating intermolecular interactions is crucial for tuning radical properties, as well as regulating their absorption bands, and thus improving the photothermal conversion efficiency. Herein, a diradical-featured organic small-molecule croconium derivative, CR-DPA-T, is reported for highly efficient utilization of solar energy. Upon aggregation, CR-DPA-T exists in dimer form, stabilized by the strong intermolecular π-π interactions, and exhibits a rarely reported high-spin state. Benefiting from the synergic effects of radical characteristics and strong intermolecular π-π interactions, CR-DPA-T powder absorbs broadly from 300 to 2000 nm. In-depth investigations with transient absorption analysis reveal that the strong intermolecular π-π interactions can promote nonradiative relaxation by accelerating internal conversion and facilitating intermolecular charge transfer (ICT) between dimeric molecules to open up faster internal conversion pathways. Remarkably, CR-DPA-T powder demonstrates a high photothermal efficiency of 79.5% under 808 nm laser irradiation. By employing CR-DPA-T as a solar harvester, a CR-DPA-T-loaded flexible self-healing poly(dimethylsiloxane) (H-PDMS) film, named as H-PDMS/CR-DPA-T self-healing film, is fabricated and employed for solar-thermal applications. These findings provide a feasible guideline for developing highly efficient diradical-featured organic photothermal materials.

Hybrid Plasmonic Nanomaterials for Hydrogen Generation and Carbon Dioxide Reduction

The successful development of artificial photosynthesis requires finding new materials able to efficiently harvest sunlight and catalyze hydrogen generation and carbon dioxide reduction reactions. Plasmonic nanoparticles are promising candidates for these tasks, due to their ability to confine solar energy into molecular regions. Here, we review recent developments in hybrid plasmonic photocatalysis, including the combination of plasmonic nanomaterials with catalytic metals, semiconductors, perovskites, 2D materials, metal-organic frameworks, and electrochemical cells. We perform a quantitative comparison of the demonstrated activity and selectivity of these materials for solar fuel generation in the liquid phase. In this way, we critically assess the state-of-the-art of hybrid plasmonic photocatalysts for solar fuel production, allowing its benchmarking against other existing heterogeneous catalysts. Our analysis allows the identification of the best performing plasmonic systems, useful to design a new generation of plasmonic catalysts.

Heterostructures Made of Upconversion Nanoparticles and Metal-Organic Frameworks for Biomedical Applications

Heterostructure nanoparticles (NPs), constructed by two single-component NPs with distinct nature and multifunctional properties, have attracted intensive interest in the past few years. Among them, heterostructures made of upconversion NPs (UCNPs) and metal-organic frameworks (MOFs) can not only integrate the advantageous characteristics (e.g., porosity, structural regularity) of MOFs with unique upconverted optical features of UCNPs, but also induce cooperative properties not observed either for single component due to their special optical or electronic communications. Recently, diverse UCNP-MOF heterostructures are designed and synthesized via different strategies and have demonstrated appealing potential for applications in biosensing and imaging, drug delivery, and photodynamic therapy (PDT). In this review, the synthesis strategies of UCNP-MOF heterostructures are first summarized, then the authors focus mainly on discussion of their biomedical applications, particularly as PDT agents for cancer treatment. Finally, the authors briefly outlook the current challenges and future perspectives of UCNP-MOF hybrid nanocomposites. The authors believe that this review will provide comprehensive understanding and inspirations toward recent advances of UCNP-MOF heterostructures.

Pillararene-based molecular-scale porous materials

This review discusses the design and syntheses of molecular-scale pillar[n]arene-based porous materials with promising applications and summarises the development of using pillar[n]arenes as the building blocks of porous materials. From the perspective of "role of participation" in the syntheses of molecular-scale pillar[n]arene-based porous materials, the content can be divided into pillar[n]arenes serving as supramolecular nanovalves on surfaces and as ligands for metal-organic frameworks and covalent organic polymers. By integrating pillararenes, which possess rigid pillar-like structures, electron-rich cavities and desirable host-guest properties, with porous polymers of large surface areas and abundant active sites, applications of the resulting materials in drug release platforms, molecular recognition, sensing, detection, gas adsorption, removal of water pollution, organic photovoltaic materials and heterogeneous catalysis can be realised simultaneously and efficiently. Finally, in the conclusions and perspectives part, we put forward the challenges and viewpoints of the current research on pillar[n]arene-based porous materials. We hope this article can provide a timely and valuable reference for researchers interested in synthetic macrocycles and porous materials.

Metal-Organic Frameworks With Variable Valence Metal-Photoactive Components: Emerging Platform for Volatile Organic Compounds Photocatalytic Degradation

With their outstanding diversities in both structures and performances, newly emerging metal-organic frameworks (MOFs) materials are considered to be the most promising artificial catalysts to meet multiple challenges in the fields of energy and environment. Especially in absorption and conversion of solar energy, a variety of MOFs can be readily designed to cover and harvest the sun irradiation of ultraviolet (UV), visible and near-infrared region through tuning both organic linkers and metal nodes to create optimal photocatalytic efficiency. Nowadays, a variety of MOFs were successfully synthesized as powerful photocatalysts for important redox reactions such as water-splitting, CO₂ reduction and aqueous environmental pollutants detoxification. MOFs applications in indoor-air VOCs pollutants cleaning, however, are less concerned partially because of limited diffusion of both gaseous pollutant molecules and photo-induced active species in very porous MOFs structures. In this mini-review, we focus on the major breakthroughs of MOFs as photocatalysts for the effective removal of indoor-air VOCs such as aldehydes, aromatics and short-chain alcohols. According to their nature of photoactive centers, herein MOFs photocatalysts are divided into two categories to comment, that is, MOFs with variable valence metal nodes as direct photoactive centers and MOFs with non-variable valence metal nodes but after combining other photoactive variable valence metal centers as excellent concentrated and concerted electron-transfer materials. The mechanisms and current challenges of the photocatalytic degradation of indoor-air VOC pollutants by these MOFs will be discussed as deeply as possible.

Piezo-Photocatalysis over Metal-Organic Frameworks: Promoting Photocatalytic Activity by Piezoelectric Effect

The built-in electric field can be generated in the piezoelectric materials under mechanical stress. The resulting piezoelectric effect is beneficial to charge separation in photocatalysis. Meanwhile, the mechanical stress usually gives rise to accelerated mass transfer and enhanced catalytic activity. Unfortunately, it remains a challenge to differentiate the contribution of these two factors to catalytic performance. Herein, for the first time, isostructural metal-organic frameworks (MOFs), i.e., UiO-66-NH₂ (Zr) and UiO-66-NH₂ (Hf), are adopted for piezo-photocatalysis. Both MOFs, featuring the same structures except for diverse Zr/Hf-oxo clusters, possess distinctly different piezoelectric properties. Strikingly, UiO-66-NH₂ (Hf) exhibits ≈2.2 times of activity compared with that of UiO-66-NH₂ (Zr) under simultaneous light and ultrasonic irradiation, though both MOFs display similar activity in the photocatalytic H₂ production without ultrasonic irradiation. Given their similar pore features and mass transfer behaviors, the activity difference is unambiguously assignable to the piezoelectric effect. As a result, the contributions of the piezoelectric effect to the piezo-photocatalysis can be clearly distinguished owing to the stronger piezoelectric property of UiO-66-NH₂ (Hf).

Engineering Near-Infrared-Excitable Metal-Organic Framework for Tumor Microenvironment Responsive Therapy

Luminescent metal-organic frameworks (MOFs), which incorporate some guest luminescent molecules/ions into MOFs, have attracted extensive attention because of their exceptional optical properties. However, traditional luminescent MOFs are mainly responsive to ultraviolet (UV) or visible light, which has limited their bioapplications due to the restrained tissue penetration depths. In this study, we have constructed a diagnostic nanoplatform UCNP@MOF consisting of upconverting metal-organic frameworks, which combine the photo-upconverting characteristics of the upconversion nanoparticles (UCNPs) with the unique physicochemical properties of Al-MOFs. Specifically, the core-shell structured UCNP@MOF nanocomposites were prepared by poly(vinylpyrrolidone) (PVP)-regulated nucleation of Al-MOF layer on the UCNP surface. When excited by a 980 nm laser light, the green signal released from UCNPs can trigger the photosensitive Al-MOFs to produce a large amount of singlet oxygen (¹O₂) for photodynamic therapy (PDT). Meanwhile, the anticancer drug, doxorubicin hydrochloride (DOX), was further incorporated into the porous structures of Al-MOFs and demonstrated the pH-responsive drug release behavior. Our results show that the near-infrared (NIR) light-induced PDT with chemotherapy (CMT) exhibits excellent antitumor effects. It is believed that the present work highlights the potential of the combination of UCNPs and MOFs and holds great promise for biomedical applications.

Facet Selectivity Guided Assembly of Nanoarchitectures onto Two-Dimensional Metal-Organic Framework Nanosheets

Facet-selective nanostructures in living systems usually exhibit outstanding optical and enzymatic properties, playing important roles in photonics, matter exchange, and biocatalysis. Bioinspired construction of facet-selective nanostructures offers great opportunities for sophisticated nanomaterials, but remains a formidable task. We have developed a macromolecule-mediated strategy for the assembly of upconversion nanoparticles (UCNPs)/two-dimensional metal-organic frameworks (2DMOFs) heterostructures with facet selectivity. Both experimental and theoretical results demonstrate that polyvinylpyrrolidone (PVP) can be utilized as an interface-selective mediator to further promote the facet-selective assembly of MOFs onto the surface of UCNPs. The UCNPs/2DMOFs nanostructures with facet selectivity display specific optical properties and show great advantages in anti-counterfeiting. Our demonstration of UCNPs/2DMOFs provides a vivid example for the controlled fabrication of facet-selective nanostructures and can promote the development of advanced functional materials for applications in biosensing, energy conversion, and information assurance.

A Full-Spectrum Porphyrin-Fullerene D-A Supramolecular Photocatalyst with Giant Built-In Electric Field for Efficient Hydrogen Production

A full-spectrum (300-850 nm) responsive donor-acceptor (D-A) supramolecular photocatalyst tetraphenylporphinesulfonate/fullerene (TPPS/C₆₀ ) is successfully constructed. The theoretical spectral efficiency of TPPS/C₆₀ is as high as 70%, offering the possibility of full-solar-spectrum light harvesting. The TPPS/C₆₀ performs a highly efficient photocatalytic H₂ evolution rate of 276.55 µmol h^-1 (34.57 mmol g^-1 h^-1 ), surpassing many reported organic photocatalysts. The D-A structure effectively promotes electron transfer from TPPS to C₆₀ , which is beneficial to the photocatalytic reaction. Specifically, a giant internal electric field in the D-A structure is built via the enhanced molecular dipole, which dramatically promotes the charge separation (CS) efficiency by 2.35 times. Transient absorption spectra results show a long-lived CS state TPPS^•+ -C₆₀ ^•- in the D-A structure, which effectively promotes participation of photogenerated electrons in the reduction reaction. Briefly, this work provides a novel approach for designing high-performance photocatalytic materials via enhancing the interfacial electric field.

Metal-Organic Frameworks as a Versatile Materials Platform for Unlocking New Potentials in Biocatalysis

Biocatalysts immobilization with nanomaterials has promoted the development of biocatalysis significantly and made it an indispensable part of catalysis industries nowadays. Metal-organic frameworks (MOFs), constructed from organic linkers and metal ions or clusters, have raised significant interests for biocatalysts immobilization in recent years. The diversity of building units, molecular-scale tunability, and modular synthetic routes of MOFs greatly expand its ability as the host to integrate with biocatalysts. In this review, the general synthetic strategies of MOFs with biocatalysts are first summarized. Then, the recent progress of MOFs as a versatile host for a series of biocatalysts, including natural enzymes, nanozymes, and organism-based biocatalysts, followed by the introduction of MOFs themselves as biocatalysts, is discussed. Furthermore, the stimuli-responsive properties of MOFs themselves or the additional functionalization of protein, polymer, and peptide within/on MOF that enable the biocatalysts with the controllable and tunable behavior are also summarized, which could unlock new potentials in biocatalysis. Finally, a perspective of the upcoming challenges, potential impacts, and future directions of biocatalytic MOFs is provided.

Y2O3:Yb3+, Tm3+/ZnO composite with a heterojunction structure and upconversion function for the photocatalytic degradation of organic dyes

Endowing photocatalytic materials with a broader range of light responses is important for improving their performance and solar energy utilization. In this study, a simple sol-gel method was used to prepare Yb³⁺/Tm³⁺-co-doped Y₂O₃ upconversion materials and Y₂O₃:Yb³⁺, Tm³⁺/ZnO (Y/Z) composite photocatalysts for the photocatalytic degradation of dyes. The Y/Z composite photocatalyst achieved degradation rates of 38%, 95%, and 89% for methyl orange, methylene blue (MB), and acid chrome blue K dye solutions, respectively, within 30 minutes. The degradation efficiency for MB after three cycles of degradation was 86%. The spherical Y₂O₃:Yb³⁺, Tm³⁺ particles had diameters of 20-50 nm and attached to the ZnO nanosheets, forming a heterojunction structure with ZnO. Fluorescence spectroscopy showed that Y₂O₃:Yb³⁺, Tm³⁺ could convert near-infrared (NIR) light into three sets of ultraviolet light (290, 320, and 360 nm) under NIR excitation. Photoluminescence spectroscopy demonstrated that the photogenerated electron-hole pair recombination probability of the composite photocatalyst was significantly lower than that of ZnO nanosheets, thereby reducing the energy loss during the migration process. Furthermore, the addition of Y₂O₃:Yb³⁺, Tm³⁺ to ZnO substantially improved the absorption capacity for ultraviolet light, which enhanced the photocatalytic activity. A possible mechanism for the enhanced photocatalytic performance of the Y/Z composites was proposed based on the synergistic effect of heterojunction formation and the photoconversion process. The composite photocatalyst with upconversion characteristics and heterogeneous structure provides a new strategy for removing organic pollutants from water.

Efficient Schottky Junction Construction in Metal-Organic Frameworks for Boosting H2 Production Activity

Manipulation of the co-catalyst plays a vital role in charge separation and reactant activation to enhance the activity of metal-organic framework-based photocatalysts. However, clarifying and controlling co-catalyst related charge transfer process and parameters are still challenging. Herein, three parameters are proposed, V transfer (the electron transfer rate from MOF to co-catalyst), D transfer (the electron transfer distance from MOF to co-catalyst), and V consume (the electron consume rate from co-catalyst to the reactant), related to Pt on UiO-66-NH2 in a photocatalytic process. These parameters can be controlled by rational manipulation of the co-catalyst via three steps: i) Compositional design by partial substitution of Pt with Pd to form PtPd alloy, ii) location control by encapsulating the PtPd alloy into UiO-66-NH2 crystals, and iii) facet selection by exposing the encapsulated PtPd alloy (100) facets. As revealed by ultrafast transient absorption spectroscopy and first-principles simulations, the new Schottky junction (PtPd (100)@UiO-66-NH2) with higher V transfer and V consume exhibits enhanced electron-hole separation and H2O activation than the traditional Pt/UiO-66-NH2 junction, thereby leading to a significant enhancement in the photoactivity.

Optimization of plasmonic metal structures for improving the hydrogen production efficiency of metal-organic frameworks

The introduction of plasmonic metals of gold (Au) nanoparticles onto metal-organic frameworks (MOFs) has been testified as an efficient approach to boost the H2 evolution ability because the excited Au particles can generate hot electrons that can then be injected into MOFs to inhibit the recombination of charges. Generally, Au particles possess two modes of polarization, which are transverse and longitudinal polarizations. However, which of the two modes is more efficient remains unclear and is yet to be disclosed. Herein, we report a strategy of finely controlling the transverse and longitudinal polarizations by gradually reducing the length, without changing the width of Au rods, and then combining with MOF Pt@MIL-125 to construct Pt@MIL-125/Au Schottky junctions, for investigating the polarization mode effects. The results indicate that with the reduction in the length of Au rods from 67 nm to 38 nm, the transverse polarization will be increased, which can lead to a significant enhancement in the electron-hole separation efficiency and H2 generation activity. When Au is in spherical shape, the transverse polarization effect reaches the highest level, thereby achieving the highest H2 production rate of 265.1 μmol g-1 h, which is 1.6 times more than that of 67 nm Au rods. The enhancement can be attributed to the significant accelerated electron transfer rate induced by transverse polarization and evidenced by ESR analysis. The results indicate that the transverse polarization is more efficient for hot electron injection and highlight that the Au sphere is a more appropriate candidate for producing the maximum SPR effect during photocatalysis.