Precise Spatial-Designed Metal-Organic-Framework Nanosheets for Efficient Energy Transfer and Photocatalysis

Donor-acceptor mixed-ligand MOF with energy transfer-mediated high-efficiency singlet oxygen generation for boosted organic photosynthesis

Integrating energy donor and acceptor chromophores as ligands within one MOF for advanced artificial photosynthesis is of great interest but appears to be a major challenge. Herein, via a simple one-pot synthetic strategy, an energy acceptor porphyrin ligand 5,15-di(p-benzoato)porphyrin (H2DPBP) was successfully integrated into an energy donor 1,4-naphthalenedicarboxylic acid (H2NDC)-based MOF (UiO-66-NDC) to construct a mixed-ligand MOF, donated as UiO-66-NDC-H2DPBP. Benefiting from the ample overlap between the emission spectrum of H2NDC and the absorption spectrum of H2DPBP, an efficient energy transfer (EnT) process from the donor H2NDC to the acceptor H2DPBP within UiO-66-NDC-H2DPBP can occur and be captured by time-resolved spectroscopy. Furthermore, the singlet oxygen (1O2) generation efficiency of UiO-66-NDC-H2DPBP mediated by this EnT process as well as the EnT process from the triplet state (T1) of the photosensitizer H2DPBP ligand to the ground state of molecular oxygen (3O2) upon light irradiation can be maximized via simply regulating the loading amount of H2DPBP, leading to boosted photocatalytic activities toward important aerobic oxidation reactions of amines and sulfides, even under sunlight and ambient air. This work explores an avenue to construct high-efficiency energy donor and acceptor-based light-harvesting systems by utilizing mixed-ligand MOFs as platforms to advanced artificial photosynthesis.

Multivariate Tuning of Photosensitization in Mixed-Linker Metal-Organic Frameworks for Efficient CO2 Reduction

Photosensitization is a powerful approach for enhancing the photocatalyst performance by improving light absorption, energy transfer, and charge separation. However, achieving high efficiency requires precise control over photosensitizers, catalytic centers, and their interactions, which remain challenging in heterogeneous systems. Herein, we develop multivariate zirconium metal-organic frameworks (MOFs) with mixing linkers and tunable defects that enable unprecedented control over photosensitizers, catalytic centers, and their ratios, creating an efficient platform for CO2 reduction. These MOFs integrate triphenylamine, phenoxazine, or phenothiazine-based linkers as photosensitizers and metal porphyrin linkers (metal = Fe, Co, Ni, and Zn) as CO2 reduction catalytic centers. Furthermore, the defect tolerance of robust Zr6 nodes allows for a systematic variation in linker ratios by introducing missing linker defects. By fine-tuning the photosensitizers, catalytic metal centers, and their ratios, we achieved an optimized photocatalyst with CO2-to-CO reduction rates of 247.8 μmol gcat.-1 h-1, representing a 17-fold enhancement over homogeneous analogues. Transient spectra and density functional theory calculations reveal the critical role of the framework structure in promoting efficient intrareticular energy transfer and charge separation. This study highlights the unique advantage of MOF platforms in the multivariate tuning of photocatalysts, paving the way for advanced artificial photosynthetic systems.

Polychromatic Electrochemiluminescence Imaging of Single Heteroligand Metal-Organic Crystals

Conventional polychromatic electrochemiluminescence (ECL) imaging is realized with the several separated luminophores at the different potentials. In this study, an emerging polychromatic ECL imaging system was constructed based on single heteroligand metal-organic framework (MOF) crystals as nanoemitters through an intrareticular energy transfer process. The heteroligand MOF crystals, named h-NJU-241, were coassembled of meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) with 1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy) ligand using benzoic acid catalyst with coordination ability, leading to the conjugated spacing of 0.624 nm between two ligands. Remarkably, an energy transfer efficiency of 92.2% was achieved when the coordination weight ratio of TCPP acceptor and TBAPy donor was only 1.87‰. Different from monoligand MOFs, the heteroligand h-NJU-241 exhibits dual ECL emissions in both blue and red regions at one step applied potential, which is first example of polychromatic ECL imaging for single MOF crystals. Furthermore, by adjusting the reaction conditions, the morphology distribution of porphyrin within the crystal can be dynamically controlled, providing a tailored crystal platform for decoding fundamentals in polychromatic ECL imaging.

Dual-Fluorinated Ni Single Atom Catalyst for Efficient Artificial Photosynthetic Diluted CO2 Reduction

The development of efficient photocatalysts to convert dilute CO2 from flue gas into high value-added products is a promising approach to achieving carbon neutrality. In this work, a dual-fluorinated Ni single atom photocatalyst is reported for the photoreduction of diluted CO2 to CO. Under a dilute CO2 (10%) atmosphere, TPB-SA2F-Ni achieves the highest reported CO yield (30344.4 µmol g-1 h-1) among heterogeneous catalytic systems with a CO selectivity of 98%. Kevin probe force microscopy and photoelectrochemical characterizations indicate that dual-fluorination strategy enhances photoexcited electron transfer between the photosensitizer and photocatalyst by optimizing the conjugated electronic structure. Pore size distribution and CO2 adsorption experiments show that the uniform microporous structure induced by the dual-F site further enhanced the ability of the Ni-N2O2 active site to capture CO2 molecules. Density functional theory calculations indicate that the high CO yield of TPB-SA2F-Ni stems from a lowered energy barrier for *COOH intermediate formation.

Highly Efficient Solvent-Free Cyanosilylation of Aldehydes Catalyzed by Bilayered Two-Dimensional Metal-Organic Frameworks

While metal-organic frameworks (MOFs) are promising for heterogeneous catalysis and mechanistic investigations due to their well-defined active sites, high porosity, large surface area, and structural tunability, two-dimensional (2D) MOFs exhibit superior catalytic efficiency over three-dimensional (3D) MOFs by offering higher specific surface areas and reduced diffusion limitations, thus enhancing active site exposure and substrate accessibility. In this work, two novel bilayered 2D MOFs, Mg3(TPHB)2(H2O)6·(DMF)12 (Mg-TPHB-MOF) and Mn3(TPHB)2(H2O)6·(DMF)16 (Mn-TPHB-MOF), were synthesized, and their efficacy as Lewis acid catalysts in the solvent-free cyanosilylation of aldehydes was investigated. Both MOFs exhibited remarkable catalytic activity, with Mg-TPHB-MOF achieving complete conversion of benzaldehyde within 10 min at room temperature. This catalytic performance surpasses that of many previously reported MOF catalysts for the same reaction, highlighting the potential of 2D MOFs in catalysts. To gain deeper insights into the catalytic mechanism and the superior performance of Mg-TPHB-MOF, computational studies were conducted to determine the free energy profiles of the reaction pathways with and without the catalyst. The results of these calculations corroborated the experimental findings, indicating a lower energy barrier for the Mg-TPHB-MOF-catalyzed reaction. Furthermore, both MOFs demonstrated good reusability over five catalytic cycles, maintaining high conversion rates and structural integrity.

Postsynthetic Modification of Metal-Organic Layers

ConspectusMetal-organic layers (MOLs), as a subclass of two-dimensional (2D) metal-organic frameworks (MOFs), have gained prominence in materials science by combining the structural versatility of MOFs with the unique physical and chemical properties of 2D materials. MOLs consist of metal oxide clusters connected by organic ligands, forming periodically extended 2D architectures with tunable properties and large surface areas. These characteristics endow MOLs with significant potential for applications in catalysis, sensing, energy storage, and biomedicine.The synthesis of MOLs predominantly follows two key pathways: top-down exfoliation of bulk layered MOFs and bottom-up assembly from molecular building units. The exfoliation method allows for the isolation of ultrathin MOL sheets from bulk precursors, but scalability and structural defects present ongoing challenges. In contrast, the bottom-up assembly offers more precise control over structural design, enabling the formation of MOLs with tailored chemical functionalities and morphologies. By carefully selecting linkers and synthetic conditions, researchers have successfully constructed MOLs with diverse geometric configurations including linear, triangular, and rectangular ligand motifs. Nevertheless, achieving consistent monolayer formation and controlling lateral dimensions remain critical challenges for the widespread application of these materials.A defining advantage of MOLs is their exceptional amenability to postsynthetic modification (PSM). PSM strategies enable fine-tuning of MOL properties and the introduction of novel functionalities without compromising the integrity of the underlying framework. Four principal approaches to PSM have been established: (1) linker modification, where additional coordination sites facilitate selective metalation or functional group incorporation; (2) secondary building unit (SBU) modification, using replaceable sites perpendicular to the MOL plane for targeted functionalization; (3) dual modification, integrating linker and SBU functionalization to achieve complex multifunctional platforms; and (4) multilevel assembly, incorporating MOLs into larger hierarchical architectures such as biomimetic systems and composite materials.These versatile modification strategies have unlocked novel applications of MOLs, including single-site catalysis, photocatalysis, and artificial photosynthetic systems. For instance, MOLs functionalized with transition metal complexes have more accessible reactive sites than conventional MOFs for faster substrate transport. Additionally, MOLs interfaced with biomimetic systems, such as liposomes and proteins, have demonstrated significant promise in photochemical energy conversion and selective oxidation processes.Despite these advancements, several key obstacles persist. Achieving uniform monolayer thickness while preventing multilayer aggregation remains a formidable task, necessitating deeper insights into the thermodynamic and kinetic factors governing MOL growth. Furthermore, the behavior of MOLs during drying, adsorption, and structural modification often deviates from classical models, suggesting the involvement of complex interfacial phenomena that warrant further investigation. Addressing these challenges will be crucial for harnessing the full potential of MOLs in next-generation functional materials.In summary, MOLs represent a versatile and dynamic class of materials that offer opportunities for innovation across diverse scientific disciplines. By advancing synthetic methodologies and deepening our understanding of postsynthetic modification strategies, researchers can continue to expand the functional landscape of MOLs, paving the way for transformative applications in catalysis, energy conversion, and beyond.

Interface Engineering of MOF Nanosheets for Accelerated Redox Kinetics in Lithium-Sulfur Batteries

Modifying the separator is considered as an effective strategy for achieving high performance lithium-sulfur (Li-S) batteries. However, most modification layers are excessively thick, with catalytic active sites primarily located within the material's interior. This configuration severely impacts Li+ transport and the efficient catalytic conversion of polysulfides. Therefore, there is an urgent need to develop a multifunctional separator that integrates ultrathin design, catalytic activity, and ion sieving capabilities. Herein, we successfully linked TCPP(Ni) as a secondary ligand with Zr-BTB nanosheets to create an ultra-thin separator modification layer (Zr-TCPP(Ni)) with efficient ion sieving and catalytic properties. The resultant multifunctional separators provide robust ion sieving capabilities that promote rapid Li+ transport and intercept polysulfides shuttling. Therefore, The Zr-TCPP(Ni)@PP cell maintains 70.0 % of its initial capacity after 600 cycles at a high rate of 3 C, while achieving an impressive areal capacity of 4.55 mA h cm-2 even with high sulfur content of 80 wt% at 0.5 C. This work provides valuable insights for rational design of MOF interface engineering in high energy density Li-S batteries.

Metal-organic frameworks for the separation of xylene isomers

Xylene isomers, including para-xylene (pX), meta-xylene (mX), ortho-xylene (oX), and ethyl benzene (EB), are important raw materials in industry. The separation of xylene isomers has been recognized as one of the "seven chemical separations to change the world". However, because of their similar physicochemical properties, totally separating four xylene isomers has remained a big challenge until now. Metal-organic frameworks (MOFs) have emerged as promising separators to achieve this goal because MOFs synergistically provide multiple mechanisms at the molecular scale. In this review, we summarize the recent progress of MOFs as separators for the separation of xylenes based on four main separation mechanisms: the molecular sieving effect, gating mechanism, thermodynamic interactions, and kinetic diffusion. We concentrate on the applications of MOFs in the field of chromatography, single-component vapor adsorption, liquid-phase competitive adsorption, breakthrough, and membrane separation. Finally, we conclude with the possible direction for designing high-performance MOF separators and briefly discuss the existing challenges in this area.

Efficient electrochemiluminescence sensor utilizing Zr-PyTCPPMOF for swift hydrogen sulfide detection

The ultrahigh-sensitive detection of H2S is reported using a novel dual-ligand metal-organic framework (MOF) electrochemiluminescence (ECL) sensor. By combining tetrakis(4-carboxyphenyl) porphyrin (TCPP) and 1,3,6,8-tetrakis(4-carboxyphenyl) pyrene (TBAPy) as ligands and employing zirconium as the metal source, a spindle-shaped Zr-PyTCPPMOF was successfully designed and synthesized. Notably, the multiple nitrogen structures of porphyrin provided abundant binding sites for sulfur (S), further enhancing the ECL signal of Zr-PyTCPPMOF. The sensor shows a good linear relationship in the 0.01-100 μM range, with a detection limit reaching 1.18 nM (S/N = 3). When analyzing actual serum samples, the recovery was between 96.6 and 106.2%. Ultimately, the dual-ligand ECL platform based on Zr-PyTCPPMOF achieved trace detection of H2S, which is expected to provide reliable technical support for early environmental monitoring and disease diagnosis.

Sequential Energy and Electron Transfer in Metal-Organic Frameworks

This study presents the design and characterization of a triad metal-organic framework (MOF) system composed of pyrene, porphyrin, and phenyl-C61-butyric acid (PCBA) for efficient energy and electron transfer processes mimicking natural photosynthesis. The triad MOF, synthesized through a mixed-ligand approach followed by postsynthetic modification, demonstrates sequential energy transfer from pyrene to porphyrin, followed by electron transfer to the PCBA acceptor. Time-resolved photoluminescence (TRPL) spectroscopy was employed to investigate the dynamics of energy and charge transfer, revealing fast interligand energy transfer and subsequent charge separation in the MOF structure. The PCBA-functionalized MOF (PCBA@nMLM) exhibited a significantly enhanced photocatalytic performance compared to the nonfunctionalized counterpart, particularly in the selective aerobic oxidation of sulfides to sulfoxides under visible light irradiation. The enhanced photocatalytic activity is attributed to the prolonged charge separation facilitated by the PCBA moieties, as confirmed by electrochemical impedance spectroscopy (EIS) and transient photocurrent measurements. This work highlights the potential of MOF-based systems in artificial photosynthesis and other photocatalytic applications by effectively harnessing solar energy through optimized energy and charge transfer mechanisms.

Reticular Materials for Photocatalysis

Photocatalysis leverages solar energy to overcome the thermodynamic barrier, enabling efficient chemical reactions under mild conditions. It can greatly reduce reliance on traditional energy sources and has attracted significant research interest. Reticular materials, including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), represent a class of crystalline materials constructed from molecular building blocks linked by coordination and covalent bonds, respectively. Reticular materials function as heterogeneous catalysts, combining well-defined structures and high tailorability akin to homogeneous catalysts. In this review, the regulation of light absorption, charge separation, and surface reactions in the photocatalytic process through precise molecular-level design based on the features of reticular materials is elaborated. Notably, for MOFsmicroenvironment modulation around catalytic sites affects photocatalytic performance is delved, with emphasis on their unique dynamic and flexible microenvironments. For COFs, the inherent excitonic effects due to their fully organic nature is discussed and highlight the strategies to regulate excitonic effects for charge- and/or energy-transfer-mediated photocatalysis. Finally, the current challenges and future directions in this field, aiming to provide a comprehensive understanding of how reticular materials can be optimized for enhanced photocatalysis is discussed.

Artificial photosynthetic system for diluted CO2 reduction in gas-solid phase

Rational design of robust photocatalytic systems to direct capture and in-situ convert diluted CO2 from flue gas is a promising but challenging way to achieve carbon neutrality. Here, we report a new type of host-guest photocatalysts by integrating CO2-enriching ionic liquids and photoactive metal-organic frameworks PCN-250-Fe2M (M = Fe, Co, Ni, Zn, Mn) for artificial photosynthetic diluted CO2 reduction in gas-solid phase. As a result, [Emim]BF4(39.3 wt%)@PCN-250-Fe2Co exhibits a record high CO2-to-CO reduction rate of 313.34 μmol g-1 h-1 under pure CO2 atmosphere and 153.42 μmol g-1 h-1 under diluted CO2 (15%) with about 100% selectivity. In scaled-up experiments with 1.0 g catalyst and natural sunlight irradiation, the concentration of pure and diluted CO2 (15%) could be significantly decreased to below 85% and 10%, respectively, indicating its industrial application potential. Further experiments and theoretical calculations reveal that ionic liquids not only benefit CO2 enrichment, but also form synergistic effect with Co2+ sites in PCN-250-Fe2Co, resulting in a significant reduction in Gibbs energy barrier during the rate-determining step of CO2-to-CO conversion.

Strategy to Efficient Photodynamic Therapy for Antibacterium: Donor-Acceptor Structure in Hydrogen-Bonded Organic Framework

While the construction of a donor-acceptor (D-A) structure has gained great attention across various scientific disciplines, such structures are seldomly reported within the field of hydrogen-bonded organic frameworks (HOFs). Herein, a D-A based HOF is synthesized, where the adjacent D-A pairs are connected by hydrogen bonds instead of the conventionally employed covalent bonds. This structural feature imparts material with a reduced energy gap between excited state and triplet state, thereby facilitating the intersystem crossing (ISC) and boosting the generation rate of single oxygen (quantum yield = 0.98). Consequently, the resulting material shows high performance for antimicrobial photodynamic therapy (PDT). The impact of D-A moiety is evident when comparing this finding to a parallel study conducted on an isoreticular HOF without a D-A structure. The study presented here provides in-depth insights into the photophysical properties of D-A pair in a hydrogen-bonded network, opening a new avenue to the design of innovative materials for efficient PDT.

Dimensional Reduction of Metal-Organic Frameworks for Photocatalytic Synthesis of Fused Tetracyclic Heterocycles

Heterogeneous palladium catalysts with high efficiency, high Pd atom utilization, simplified separation, and recycle have attracted considerable attention in the field of synthetic chemistry. Herein, we reported a zirconium-based two-dimensional metal-organic framework (2D-MOF)-based Pd(II) photocatalyst (Zr-Ir-Pd) by merging the Ir photosensitizers and Pd(II) species into the skeletons of the 2D-MOF for the Pd(II)-catalyzed oxidation reaction. Morphological and structural characterization identified that Zr-Ir-Pd with a specific nanoflower-like structure consists of ultrathin 2D-MOF nanosheets (3.85 nm). Due to its excellent visible-light response and absorption capability, faster transfer and separation of photogenerated carriers, more accessible Pd active sites, and low mass transfer resistance, Zr-Ir-Pd exhibited boosted photocatalytic activity in catalyzing sterically hindered isocyanide insertion of diarylalkynes for the construction of fused tetracyclic heterocycles, with up to 12 times the Pd catalyst turnover number than the existing catalytic systems. In addition, Zr-Ir-Pd inhibited the competitive agglomeration of Pd(0) species and could be reused at least five times, owing to the stabilization of 2D-MOF on the single-site Pd and Ir sites. Finally, a possible mechanism of the photocatalytic synthesis of fused tetracyclic heterocycles catalyzed by Zr-Ir-Pd was proposed.

Panchromatic Light-Harvesting Three-Dimensional Metal Covalent Organic Frameworks for Boosting Photocatalysis

Constructing artificial photocatalysts with panchromatic solar energy utilization remains an appealing challenge. Herein, two complementary photosensitizers, [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) and porphyrin dyes, have been cosensitized in metal covalent organic frameworks (MCOFs), resulting in the MCOFs with strong light absorption covering the full visible spectrum. Under panchromatic light irradiation, the cosensitized MCOFs exhibited remarkable photocatalytic H2 evolution with an optimum rate of up to 33.02 mmol g-1 h-1. Even when exposed to deep-red light (λ = 700 ± 10 nm), a commendable H2 production (0.79 mmol g-1 h-1) was still obtained. Theoretical calculation demonstrated that the [Ru(bpy)3]2+ and porphyrin modules in our MCOFs have a synergistic effect to trigger an interesting dual-channel photosensitization pathway for efficient light-harvesting and energy conversion. This work highlights the potential of combining multiple PSs in MCOFs for panchromatic photocatalysis.

Covalent organic frame based high-performance nanocomposite for construction of ATP sensor

In this work, a novel covalent organic frame (TAPT-TFPB COF) with self-enhanced photoelectric activity was prepared for decorating on conductive single-walled carbon nanotubes (SWCNT) to synthetize a high-performance photoelectric nanocomposite (COF/SWCNT), in which the interfacial charge separation and photogenerated carrier migration rate was significantly improved to obtain desiring photoelectric conversion efficiency for generating an extremely high photocurrent. Accordingly, the synthetic COF/SWCNT was ingeniously applied in the fabrication of ultrasensitive photoelectrochemical (PEC) biosensor for realizing the trace ATP detection by integrating with an Exo III-assisted dual DNA recycling amplification strategy. The recycling amplification could efficiently convert trace target ATP into plentiful output DNA, which ingeniously triggered the hybridization chain reaction (HCR) to generate a long DNA strand with substantial quencher manganese porphyrin (MnPP) loading to depress the photocurrent of COF/SWCNT. The experimental data showed that proposed biosensor had a detection range from 10 fmol L-1 to 10 nmol L-1 with the detection limit as low as 2.75 fmol L-1 (S/N = 3). In addition, this proposed biosensor showed excellent analytical performance in terms of stability, specificity and reproducibility, providing a possibility to accomplish sensitive and accurate in vitro diagnosis.

Enhanced Charge Transfer Process and Photocatalytic Activity over a Phosphonate-based MOF via Amorphization Strategy

Recently, amorphous materials have gained great attention as an emerging kind of functional material, and their characteristics such as isotropy, absence of grain boundaries, and abundant defects are very likely to outrun the disadvantages of crystalline counterparts, such as low conductivity, and ultimately lead to improved charge transfer efficiency. Herein, we investigated the effect of amorphization on the charge transfer process and photocatalytic performance with a phosphonate-based metal-organic framework (FePPA) as the research object. Comprehensive experimental results suggest that compared to crystalline FePPA, amorphous FePPA has more distorted metal nodes, which affects the electron distribution and consequently improves the photogenerated charge separation efficiency. Meanwhile, the distorted metal nodes in amorphous FePPA also greatly promote the adsorption and activation of O2. Hence, amorphous FePPA exhibits a better performance of photocatalytic C(sp3)-H bond activation for selective oxidation of toluene to benzaldehyde. This work illustrates the advantages of amorphous MOFs in the charge transfer process, which is conducive to the further development of high performance MOFs-based photocatalysts.

Organic Donor-Acceptor Systems for Photocatalysis

Organic semiconductor materials are considered to be promising photocatalysts due to their excellent light absorption by chromophores, easy molecular structure tuning, and solution-processable properties. In particular, donor-acceptor (D-A) type organic photocatalytic materials synthesized by introducing D and A units intra- or intermolecularly, have made great progress in photocatalytic studies. More and more studies have demonstrated that the D-A type organic photocatalytic materials combine effective carrier separation, tunable bandgap, and sensitive optoelectronic response, and are considered to be an effective strategy for enhancing light absorption, improving exciton dissociation, and optimizing carrier transport. This review provides a thorough overview of D-A strategies aimed at optimizing the photocatalytic performance of organic semiconductors. Initially, essential methods for modifying organic photocatalytic materials, such as interface engineering, crystal engineering, and interaction modulation, are briefly discussed. Subsequently, the review delves into various organic photocatalytic materials based on intramolecular and intermolecular D-A interactions, encompassing small molecules, conjugated polymers, crystalline polymers, supramolecules, and organic heterojunctions. Meanwhile, the energy band structures, exciton dynamics, and redox-active sites of D-A type organic photocatalytic materials under different bonding modes are discussed. Finally, the review highlights the advanced applications of organic photocatalystsand outlines prospective challenges and opportunities.

Porphyrin-Based Metal-Organic Framework Materials: Design, Construction, and Application in the Field of Photocatalysis

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light from ultraviolet to visible light regions, and their structures and properties can be facilely regulated by altering their peripheral groups or central metal ions. Porphyrin-based MOFs constructed from porphyrin ligands and metal nodes combine the unique features of porphyrins and MOFs as well as overcoming their respective limitations. This paper reviewed the design and construction, light absorption and charge transfer pathways, and strategy for improving the photocatalytic performance of porphyrin-based MOFs, and highlighted the recent progress in the field of CO2 reduction, hydrogen evolution, organic synthesis, organic pollutant removal, and nitrogen fixation. The intrinsic relationships between the structure and the property of porphyrin-based MOFs received special attention, especially the relationships between the arrangements of porphyrin ligands and metal nods and the charge transfer mechanism. We attempted to provide more valuable information for the design and construction of advanced photocatalysts in the future. Finally, the challenges and future perspectives of the porphyrin-based MOFs are also discussed.

Integrating Photoactive Ligands into Crystalline Ultrathin 2D Metal-Organic Framework Nanosheets for Efficient Photoinduced Energy Transfer

3D metal-organic frameworks (MOFs) have gained attention as heterogeneous photocatalysts due to their porosity and unique host-guest interactions. Despite their potential, MOFs face challenges, such as inefficient mass transport and limited light penetration in photoinduced energy transfer processes. Recent advancements in organic photocatalysis have uncovered a variety of photoactive cores, while their heterogenization remains an underexplored area with great potential to build MOFs. This gap is bridged by incorporating photoactive cores into 2D MOF nanosheets, a process that merges the realms of small-molecule photochemistry and MOF chemistry. This approach results in recyclable heterogeneous photocatalysts that exhibit an improved mass transfer efficiency. This research demonstrates a bottom-up synthetic method for embedding photoactive cores into 2D MOF nanosheets, successfully producing variants such as PCN-641-NS, PCN-643-NS, and PCN-644-NS. The synthetic conditions were systematically studied to optimize the crystallinity and morphology of these 2D MOF nanosheets. Enhanced host-guest interactions in these 2D structures were confirmed through various techniques, particularly solid-state NMR studies. Additionally, the efficiency of photoinduced energy transfer in these nanosheets was evidenced through photoborylation reactions and the generation of reactive oxygen species (ROS).

Reticular framework materials for photocatalytic organic reactions

Photocatalytic organic reactions, harvesting solar energy to produce high value-added organic chemicals, have attracted increasing attention as a sustainable approach to address the global energy crisis and environmental issues. Reticular framework materials, including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), are widely considered as promising candidates for photocatalysis owing to their high crystallinity, tailorable pore environment and extensive structural diversity. Although the design and synthesis of MOFs and COFs have been intensively developed in the last 20 years, their applications in photocatalytic organic transformations are still in the preliminary stage, making their systematic summary necessary. Thus, this review aims to provide a comprehensive understanding and useful guidelines for the exploration of suitable MOF and COF photocatalysts towards appropriate photocatalytic organic reactions. The commonly used reactions are categorized to facilitate the identification of suitable reaction types. From a practical viewpoint, the fundamentals of experimental design, including active species, performance evaluation and external reaction conditions, are discussed in detail for easy experimentation. Furthermore, the latest advances in photocatalytic organic reactions of MOFs and COFs, including their composites, are comprehensively summarized according to the actual active sites, together with the discussion of their structure-property relationship. We believe that this study will be helpful for researchers to design novel reticular framework photocatalysts for various organic synthetic applications.

Mesoporous Mixed-Metal-Organic Framework Incorporating a [Ru(Phen)3]2+ Photosensitizer for Highly Efficient Aerobic Photocatalytic Oxidative Coupling of Amines

[Ru(Phen)₃]²⁺ (phen = phenanthroline) as a very classical photosensitizer possesses strong absorption in the visible range and facilitates photoinduced electron transfer, which plays a vital role in regulating photochemical reactions. However, it remains a significant challenge to utilize more adequately and exploit more efficiently the ruthenium-based materials due to the uniqueness, scarcity, and nonrenewal of the noble metal. Here, we integrate the intrinsic advantages of the ruthenium-based photosensitizer and mesoporous metal-organic frameworks (meso-MOFs) into a [Ru(Phen)₃]²⁺ photosensitizer-embedded heterometallic Ni(II)/Ru(II) meso-MOF (LTG-NiRu) via the metalloligand approach. LTG-NiRu, with an extremely robust framework and a large one-dimensional (1D) channel, not only makes ruthenium photosensitizer units anchored in the inner wall of meso-MOF tubes to circumvent the problem of product/catalyst separation and recycling of catalysts in heterogeneous systems but also exhibits exceptional activities for the aerobic photocatalytic oxidative coupling of amine derivatives as a general photocatalyst. The conversion of the light-induced oxidative coupling reaction for various benzylamines is ∼100% in 1 h, and more than 20 chemical products generated by photocatalytic oxidative cycloaddition of N-substituted maleimides and N,N-dimethylaniline can be synthesized easily in the presence of LTG-NiRu upon visible light irradiation. Moreover, recycling experiments demonstrate that LTG-NiRu is an excellent heterogeneous photocatalyst with high stability and excellent reusability. LTG-NiRu represents a great potential photosensitizer-based meso-MOF platform with an efficient aerobic photocatalytic oxidation function that is convenient for gram-scale synthesis.

Peptide-derived coordination frameworks for biomimetic and selective separation

Peptide-derived metal-organic frameworks (PMOFs) have emerged as a class of biomimetic materials with attractive performances in analytical and bioanalytical chemistry. The incorporation of biomolecule peptides gives the frameworks conformational flexibility, guest adaptability, built-in chirality, and molecular recognition ability, which greatly accelerate the applications of PMOFs in enantiomeric separation, affinity separation, and the enrichment of bioactive species from complicated samples. This review focuses on the recent advances in the engineering and applications of PMOFs in selective separation. The unique biomimetic size-, enantio-, and affinity-selective performances for separation are discussed along with the chemical structures and functions of MOFs and peptides. Updates of the applications of PMOFs in adaptive separation of small molecules, chiral separation of drug molecules, and affinity isolation of bioactive species are summarized. Finally, the promising future and remaining challenges of PMOFs for selective separation of complex biosamples are discussed.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Mixed-Component Metal-Organic Framework for Boosting Synergistic Photoactivation of C(sp3)-H and Oxygen

Synergistic catalysis is an efficient and powerful strategy for simultaneously activating reactants by multiple active sites to promote the efficiency of difficult and challenging catalytic reactions. Meanwhile, enzymes with multi-active-site synergistic catalytic properties possessing high efficiency and high selectivity have become the goal pursued in the field of catalytic chemistry in recent years. Metal-organic frameworks (MOFs), as an effective heterogeneous catalytic platform, that can integrate multiple active sites for synergistic catalysis like enzymatic systems have recently attracted interest. Herein, we report a doubly interpenetrated metal-organic framework with dual active sites, Mn^III-porphyrin sites to directly activate molecular oxygen and fluoren-9-one sites to produce a hydrogen atom transfer (HAT) agent by the proton-coupled electron transfer (PCET) process to simultaneously activate inert C(sp³)-H bonds for efficient inert C(sp³)-H bond oxidation under mild conditions. The bifunctional mixed-component MOF structure forced the two catalytic sites closer together to a more suitable distance, exhibiting high photocatalytic activity for inert C(sp³)-H bond oxidation with almost unique selectivity under mild conditions. The density functional theory (DFT) calculation of free energy during the whole catalytic process demonstrated that it is likely that the synergistic catalytic process occurred in the interframework to accelerate the catalytic reaction. The assembling mixed-component MOF for synergistic catalysis would be a prospective approach for the inert C(sp³)-H photoactivation and functionalization.

Enhancing the Photocatalytic Degradation Efficiency of Dyes of Copper-Based Metal-Organic Frameworks through a Dimension-Induced Structural Strategy

Photocatalytic degradation of pollutants is an effective environment purification strategy. Metal-organic frameworks (MOFs) have attracted extensive attention in the field of photocatalysis owing to their structural diversity, uniform cavity, and large specific surface area. However, poor electrical conductivity, light absorption, and water stability restrict their development. The tailorable structure of MOFs may effectively overcome these limitations. Herein, three Cu-based MOFs (complexes 1-3) with one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, respectively, were successfully prepared by introducing different uncoordinated ligands and adjusting the ligand/metal salt ratio. Among them, complex 1 with a 1D chain was constructed as a typical J-type aggregation by π-π stacking interactions between adjacent naphthalene rings. This intermolecular aggregation mode enhances strong exciton coupling between conjugated rings, reduces the transition energy, expands the intrinsic light absorption edge, and provides a channel for electron transport, thus improving the charge-separation efficiency. As expected, complex 1 with a 1D chain structure exhibited excellent Fenton-like catalytic activity. The apparent reaction rates were 3.2 and 2.0 times higher than those of 2D and 3D MOFs, respectively.

Functionalized MOF-Based Photocatalysts for CO2 Reduction

Metal-organic frameworks (MOFs) materials have become a research forefront in the field of photocatalytic CO₂ reduction attributed to their ultra-high specific surface area, adjustable structure, and abundant catalytic active sites. Particularly, MOFs can be facilely tuned to match CO₂ photoreduction by utilizing post-modification of metal nodes, functionalization of organic linkers, and combination with other active materials. Herein, the recent advances in the construction strategy of MOF-based photocatalysts materials for CO₂ reduction are highlighted. Some systematic modification strategies on MOF-based photocatalysts are also discussed, such as modification of metal sites and organic ligands, construction of heterojunction, introduction of single/dual-atom, and strain engineering. Finally, the future development directions of MOF-based photocatalysts in the field of CO₂ reduction are presented.

Metal-Organic Framework-Based Photocatalysis for Solar Fuel Production

Metal-organic frameworks (MOFs) represent a novel class of crystalline inorganic-organic hybrid materials with tunable semiconducting behavior. MOFs have potential for application in photocatalysis to produce sustainable solar fuels, owing to their unique structural advantages (such as clarity and modifiability) that can facilitate a deeper understanding of the structure-activity relationship in photocatalysis. This review takes the photocatalytic active sites as a particular perspective, summarizing the progress of MOF-based photocatalysis for solar fuel production; mainly including three categories of solar-chemical conversions, photocatalytic water splitting to hydrogen fuel, photocatalytic carbon dioxide reduction to hydrocarbon fuels, and photocatalytic nitrogen fixation to high-energy fuel carriers such as ammonia. This review focuses on the types of active sites in MOF-based photocatalysts and discusses their enhanced activity based on the well-defined structure of MOFs, offering deep insights into MOF-based photocatalysis.

Spatial Regulation of Acceptor Units in Olefin-Linked COFs toward Highly Efficient Photocatalytic H2 Evolution

Covalent organic frameworks (COFs)-based photocatalysts have received growing attention for photocatalytic hydrogen (H₂ ) production. One of the big challenges in the field is to find ways to promote energy/electron transfer and exciton dissociation. Addressing this challenge, herein, a series of olefin-linked 2D COFs is fabricated with high crystallinity, porosity, and robustness using a melt polymerization method without adding volatile organic solvents. It is found that regulation of the spatial distances between the acceptor units (triazine and 2, 2'-bipyridine) of COFs to match the charge carrier diffusion length can dramatically promote the exciton dissociation, hence leading to outstanding photocatalytic H₂ evolution performance. The COF with the appropriate acceptor distance achieves exceptional photocatalytic H₂ evolution with an apparent quantum yield of 56.2% at 475 nm, the second highest value among all COF photocatalysts and 70 times higher than the well-studied polymer carbon nitride. Various experimental and computation studies are then conducted to in-depth unveil the mechanism behind the enhanced performance. This study will provide important guidance for the design of highly efficient organic semiconductor photocatalysts.

Metal-Organic Framework Accelerated One-Step Capture and Reduction of Palladium to Catalytically Active Nanoparticles

Recovery of noble metals and in situ transforming to functional materials hold great promise in the sustainability of natural resources but remain as a challenge. Herein, the variable chemical microenvironments created by the inorganic-organic hybrid composition of metal-organic frameworks (MOFs) were exploited to tune the metal-support interactions, thus establishing an integrated strategy for recovering and reducing palladium (Pd). Assisted by sonic waves and alcoholic solvent, selective capture of Pd(II) from a complicated matrix to directly afford Pd nanoparticles (NPs) in MOFs can be achieved in one step within several minutes. Mechanism investigation reveals that the Pd binding site and the energy barriers between ionic and metallic status are sensitive to chemical environments in different frameworks. Thanks to the clean, dispersive, and uniform nature of Pd NPs, Pd@MOFs synthesized from a complicated environment exhibited high catalytic activity toward 4-nitrophenol reduction and Suzuki coupling reactions.

Atomically Dispersed Manganese on Biochar Derived from a Hyperaccumulator for Photocatalysis in Organic Pollution Remediation

Phytoremediation is a potentially cost-effective and environmentally friendly remediation method for environmental pollution. However, the safe treatment and resource utilization of harvested biomass has become a limitation in practical applications. To address this, a novel manganese-carbon-based single-atom catalyst (SAC) method has been developed based on the pyrolysis of a manganese hyperaccumulator, Phytolacca americana. In this method, manganese atoms are dispersed atomically in the carbon matrix and coordinate with N atoms to form a Mn-N₄ structure. The SAC developed exhibited a high photooxidation efficiency and excellent stability during the degradation of a common organic pollutant, rhodamine B. The Mn-N₄ site was the active center in the transformation of photoelectrons via the transfer of photoelectrons between adsorbed O₂ and Mn to produce reactive oxygen species, identified by in situ X-ray absorption fine structure spectroscopy and density functional theory calculations. This work demonstrates an approach that increases potential utilization of biomass during phytoremediation and provides a promising design strategy to synthesize cost-effective SACs for environmental applications.

Bio-Inspired Salinity-Gradient Power Generation With UiO-66-NH2 Metal-Organic Framework Based Composite Membrane

Salinity-gradient directed osmotic energy between seawater and river water has been widely considered as a promising clean and renewable energy source, as there are numerous river estuaries on our planet. In the past few decades, reverse electrodialysis (RED) technique based on cation-selective membranes has been used as the key strategy to convert osmotic energy into electricity. From this aspect, developing high-efficiency anion-selective membranes will also have great potential for capturing osmotic energy, however, remains systematically unexplored. In nature, electric eels can produce electricity from ionic gradients by using their “sub-nanoscale” protein ion channels to transport ions selectively. Inspired by this, here we developed a UiO-66-NH₂ metal-organic framework (MOF) based anion-selective composite membrane with sub-nanochannels, and achieved high-performance salinity-gradient power generation by mixing artificial seawater (0.5 M NaCl) and river water (0.01 M NaCl). The UiO-66-NH₂ metal-organic framework based composite membranes can be easily and economically fabricated with dense structure and long-term working stability in saline, and its performance of power generation can also be adjusted by pH to enhance the surface charge density of the MOF sub-nanochannels. This study will inspire the exploitation of MOFs for investigating the sub-nanochannel directed high-performance salinity-gradient energy harvesting systems based on anion-selective ion transport.

Ligand regulated metal–organic frameworks for synergistic photoredox and nickel catalysis

Synergistic photoredox and nickel catalytic cross-coupling systems have created a great attraction as a promising methodology to produce the aryl C−N bonds under mild conditions as well as extreme challenge,...