Enhancing Efficiency and Stability of Photovoltaic Cells by Using Perovskite/Zr-MOF Heterojunction Including Bilayer and Hybrid Structures

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Enhanced Fluorescence Based on Slow Light Effect of ZIF-8 Photonic Crystals for Trace 2,4,6-Trinitrophenol Detection

In response to growing concerns about public safety and environmental conservation, it is essential to develop a precise identification method for trace explosives. To improve the stability and detection sensitivity of perovskite quantum dots (PQDs) and address the issue of low porosity in traditional polymer-based photonic crystals (PhCs), this study proposed a PQD photoluminescence (PL) enhancement strategy based on the slow light effect of ZIF-8 PhCs for highly sensitive, selective, and convenient detection of 2,4,6-trinitrophenol (TNP). The slow light effect at the photonic band gap edge is the basis of amplifying the PL signal. PhCs were fabricated by the evaporation-induced self-assembly method. The diffraction wavelength overlapping the whole visible region was designed to match the emission wavelength of PQDs. Results showed that PhCs matching the PBG edge with PQDs' emission peak amplified the PL signal 11.3 times, significantly improving sensitivity for trace TNP detection with a limit as low as 2.52 nM. Moreover, there was a 13.3-fold enhancement of PQDs' fluorescence lifetime when the emission wavelength fell in the PBG range. The hydrophobic surface of ZIF-8 PhCs enhanced the PQDs' stability and moisture resistance. Furthermore, the selective quenching mechanism of TNP by the sensor was photoinduced electron transfer (PET) verified by DFT calculations and time-resolved PL decay dynamics measurements. This study demonstrated great potential for manipulating light emission enhancement by PhCs in developing efficient fluorescent sensors for trace environmental pollutant detection.

Effect of Metal-Organic Frameworks with Different Ligand Structures (ZIF-11 & ZIF-23) on the Optoelectronic Performance of Perovskite Photodetectors

Crystal engineering using passivation to reduce perovskite defects is crucial to improving the quality of perovskite crystals and optoelectronic properties. Because of their unique properties, metal-organic framework materials have been used as an emerging and effective passivator for perovskite materials and optoelectronic devices. This paper focuses on the differences in the optoelectronic properties of zeolite imidazolium ester framework materials (ZIF-11 & ZIF-23) doped with different conjugated ring ligands for perovskite photodetectors. This paper proposes a simple and effective method to dope zeolite imidazolium ester framework nanoparticles (ZIF-11 & ZIF-23) into organic-inorganic perovskite MAPbI3 films. The crystalline quality of the perovskite films was improved after doping with ZIF-11 and ZIF-23. Meanwhile, the performance of the planar photoconductive devices was significantly improved. The photoresponsivity of the photodetector doped with ZIF-23 was 0.185A/W, and the detectivity was 4.22 × 1012 Jones. The photoresponsivity of the photodetector doped with ZIF-23 was 0.164 A/W, and the detectivity was 3.27 × 1012 Jones. The devices maintained long-time operational stability, operating without significant degradation for 480 s under the 1.2 V bias voltage operating condition. In addition, we observed a significant suppression of the ion migration process in ZIF-23 for a voltage-controlled ion migration process. The potential application of perovskite and MOF heterojunction materials for image information acquisition and storage is demonstrated.

MOFs-Based Materials with Confined Space: Opportunities and Challenges for Energy and Catalytic Conversion

Metal-Organic Frameworks (MOFs) are a very promising material in the fields of energy and catalysis due to their rich active sites, tunable pore size, structural adaptability, and high specific surface area. The concepts of "carbon peak" and "carbon neutrality" have opened up huge development opportunities in the fields of energy storage, energy conversion, and catalysis, and have made significant progress and breakthroughs. In recent years, people have shown great interest in the development of MOFs materials and their applications in the above research fields. This review introduces the design strategies and latest progress of MOFs are included based on their structures such as core-shell, yolk-shell, multi-shelled, sandwich structures, unique crystal surface exposures, and MOF-derived nanomaterials in detail. This work comprehensively and systematically reviews the applications of MOF-based materials in energy and catalysis and reviews the research progress of MOF materials for atmospheric water harvesting, seawater uranium extraction, and triboelectric nanogenerators. Finally, this review looks forward to the challenges and opportunities of controlling the synthesis of MOFs through low-cost, improved conductivity, high-temperature heat resistance, and integration with machine learning. This review provides useful references for promoting the application of MOFs-based materials in the aforementioned fields.

Eu-Based Porphyrin MOF Enables High-Performance Carbon-Based Perovskite Solar Cells

The low power conversion efficiency (PCE) of hole transport materials (HTM) - free carbon-based perovskite solar cells (C-PSCs) poses a challenge. Here, a novel 2D Eu-TCPP MOF (TCPP; [tetrakis (4-carboxyphenyl) porphyrin]) sandwiched between the perovskite layer and the carbon electrode is used to realize an effective and stable HTM-free C-PSCs. Relying on the synergistic effect of both the metal-free TCPP ligand with a unique absorption spectrum and hydrophobicity and the EuO4(OH)2 chain in the Eu-TCPP MOF, defects are remarkably suppressed and light-harvesting capability is significantly boosted. Energy band alignment is achieved after Eu-TCPP MOF treatment, promoting hole collection. Förster resonance energy transfer results in improved light utilization and protects the perovskite from decomposition. As a result, the HTM-free C-PSCs with Eu-TCPP MOF reach a champion PCE of 18.13%. In addition, the unencapsulated device demonstrates outstanding thermal stability and UV resistance and keeps 80.6% of its initial PCE after 5500 h in a high-humidity environment (65%-85% RH).

Facile Tailoring of Metal-Organic Frameworks for Förster Resonance Energy Transfer-Driven Enhancement in Perovskite Photovoltaics

Förster resonance energy transfer (FRET) has demonstrated its potential to enhance the light energy utilization ratio of perovskite solar cells by interacting with metal-organic frameworks (MOFs) and perovskite layers. However, comprehensive investigations into how MOF design and synthesis impact FRET in perovskite systems are scarce. In this work, nanoscale HIAM-type Zr-MOF (HIAM-4023, HIAM-4024, and HIAM-4025) is meticulously tailored to evaluate FRET's existence and its influence on the perovskite photoactive layer. Through precise adjustments of amino groups and acceptor units in the organic linker, HIAM-MOFs are synthesized with the same topology, but distinct photoluminescence (PL) emission properties. Significant FRET is observed between HIAM-4023/HIAM-4024 and the perovskite, confirmed by spectral overlap, fluorescence lifetime decay, and calculated distances between HIAM-4023/HIAM-4024 and the perovskite. Conversely, the spectral overlap between the PL emission of HIAM-4025 and the perovskite's absorption spectrum is relatively minimal, impeding the energy transfer from HIAM-4025 to the perovskite. Therefore, the HIAM-4023/HIAM-4024-assisted perovskite devices exhibit enhanced EQE via FRET processes, whereas the HIAM-4025 demonstrates comparable EQE to the pristine. Ultimately, the HIAM-4023-assisted perovskite device achieves an enhanced power conversion efficiency (PCE) of 24.22% compared with pristine devices (PCE of 22.06%) and remarkable long-term stability under ambient conditions and continuous light illumination.

Multifunctional MOF@COF Nanoparticles Mediated Perovskite Films Management Toward Sustainable Perovskite Solar Cells

Although covalent organic frameworks (COFs) with high π-conjugation have recently exhibited great prospects in perovskite solar cells (PSCs), their further application in PSCs is still hindered by face-to-face stacking and aggregation issues. Herein, metal-organic framework (MOF-808) is selected as an ideal platform for the in situ homogeneous growth of a COF to construct a core-shell MOF@COF nanoparticle, which could effectively inhibit COF stacking and aggregation. The synergistic intrinsic mechanisms induced by the MOF@COF nanoparticles for reinforcing intrinsic stability and mitigating lead leakage in PSCs have been explored. The complementary utilization of π-conjugated skeletons and nanopores could optimize the crystallization of large-grained perovskite films and eliminate defects. The resulting PSCs achieve an impressive power conversion efficiency of 23.61% with superior open circuit voltage (1.20 V) and maintained approximately 90% of the original power conversion efficiency after 2000 h (30-50% RH and 25-30 °C). Benefiting from the synergistic effects of the in situ chemical fixation and adsorption abilities of the MOF@COF nanoparticles, the amount of lead leakage from unpackaged PSCs soaked in water (< 5 ppm) satisfies the laboratory assessment required for the Resource Conservation and Recovery Act Regulation.

Improved Photovoltaic Performance of Inverted Two-Dimensional Perovskite Solar Cells via a Simple Molecular Bridge on Buried Interface

NiOx-based two-dimensional perovskite solar cells (2D-PSCs) have the advantages of low fabrication temperature, suitable energy level matching, suppressed hysteresis, and superior stability, while the poor interfacial contacts between NiOx and perovskite layers limit the perovskite film growth and charge transfer. Herein, a simple molecule, urea, was used as a molecular modifier to form bifacial passivation on the buried interface of NiOx/perovskite, resulting in better interfacial contact and efficient bifacial passivation. We demonstrated that efficient bifacial passivation mainly comes from strong interactions between urea and NiOx or perovskite, which make urea a molecular bridge for smoother charge transfer. Moreover, urea can regulate the ratio of Ni3+/Ni2+, therefore boosting the conductivity of NiOx, and adjust the morphology of the NiOx film for better 2D-perovskite crystal growth. Besides, urea also passivates the bifacial defect states of both NiOx and perovskite film, yielding reduced defect density of the perovskite film and superior charge transfer on the buried interface. Consequently, inverted 2D-PSCs with urea modification proved significant improvements in short-circuit current density and fill factor, resulting in improved power conversion efficiency from 14.64 to 16.84% with better stability in air.

Perovskite Crystallization Regulation via Antimonene Quantum Sheets for Highly Efficient and Stable Solar Cells

The two-step deposition method offers significant advantages in the production of high-performance planar perovskite solar cells (PSCs). Nevertheless, there are still numerous challenges in regulating perovskite crystallization during the two-step process. In this work, two-dimensional (2D) material antimonene quantum sheets (AMQSs) as an additive are introduced to regulate the crystallization process of perovskite. As a result, perovskite films with high crystalline quality and vertical growth orientation are obtained by AMQSs providing heterogeneous nucleation sites with the penetration of a mixture solution of AMQSs and FAI into the PbI2 layer. Also, the influence mechanism of AMQSs on the crystallization of perovskite film is analyzed in details. At the same time, due to the chemical interaction between antimonene and the uncoordinated Pb2+, the defects in the perovskite are efficiently passivated. In addition, the energy level at the perovskite/SnO2 interface becomes more matched, leading to improved charge transport and extraction with the incorporation of AMQSs. Benefiting from the versatile AMQSs, the power conversion efficiency (PCE) of PSCs made by PbI2 + FAI:AMQSs is improved from 20.65 to 22.31% with the vastly enhanced Jsc and Voc. The ambient and operational stability of the unencapsulated PSCs fabricated using the PbI2 + FAI:AMQSs method were significantly improved, retaining 80% of the original PCE after being stored in a dark environment at a relative humidity of 30-40% for 18 days and 83% of the original PCE following continuous AM 1.5G illumination for 200 h.

Charge Carrier Dynamics at the Interface of 2D Metal-Organic Frameworks and Hybrid Perovskites for Solar Energy Harvesting

Interfacing perovskites with two-dimensional materials such as metal-organic frameworks (MOFs) for improved stability and electron or hole extraction has emerged as a promising path forward for the generation of highly efficient and stable solar cells. In this work, we examine the structural properties and excitation dynamics of two MOF-perovskite systems: UMCM309-a@MAPbI3 and ZrL3@MAPbI3. We find that precise band alignment and electronegativity of the MOF-linkers are necessary to facilitate the capture of excited charge carriers. Furthermore, we demonstrate that intraband relaxation of hot electrons to the MOF subsystem results in optically disallowed transitions across the band gap, suppressing radiative recombination. Furthermore, we elucidate the key mechanisms associated with improved structural stability afforded to the perovskites by the two-dimensional MOFs, highlighting the necessity of broad surface coverage and strong MOF-perovskite interaction.

Integrating Hybrid Perovskite Nanocrystals into Metal-Organic Framework as Efficient S-Scheme Heterojunction Photocatalyst for Synergistically Boosting Controlled Radical Photopolymerization under 980 nm NIR Light

S-scheme heterojunction photocatalyst MAPbI3@PCN-222 with light absorption extending to the NIR region is constructed by embedding organic-inorganic hybrid perovskite (MAPbI3) into porphyrinic Zr-MOF (PCN-222). Both in situ X-ray photoelectron spectroscopy, ultraviolet photoelectron spectral characterization, and photocatalytic polymerization experiment prove the formation of S-scheme heterojunction. MAPbI3@PCN-222 with a low dosage (90 ppm) displays an impressive photocatalytic ability for 980 nm light-mediated photoinduced electron/energy-transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization in air. The well-defined controllable-molecular weight polymers including block copolymers and ultrahigh-molecular weight polymers can be achieved with narrow distributions (Mw/Mn < 1.20) via rapid photopolymerization. The industrial application potential of the photocatalyst also has been proved by scale-up synthesis of polymers with low polydispersity under NIR light-induced photopolymerization in a large-volume reaction system (200 mL) with high monomer conversion up to 99%. The penetration photopolymerization through the 5 mm polytetrafluoroethylene plate and excellent photocontrollable behavior illustrate the existence of long-term photogenerated electron transfer of heterojunction and abundant free radicals in photopolymerization. The photocatalyst still retains high catalytic activity after 10 cycles of photopolymerization in air. It is revealed for the first time that the special PET-RAFT polymerization pathway is initiated by the aldehyde-bearing α-aminoalkyl radical derived from the oxidization of triethanolamine (TEOA) by the heterojunction photocatalyst. This research offers a new insight into understanding the NIR-light-activated PET-RAFT polymerization mechanism in the presence of TEOA.

Lanthanide 3D Supramolecular Framework Boosts Stable Perovskite Solar Cells with High UV Utilization

In this work, the ligand-to-metal charge transition and Förster resonance energy transfer process is exploited to derive lanthanide-organic framework (Tb-cpon) modified perovskite solar cells (PSCs) with enhanced performance under UV irradiation. Tb-cpon-modified PSCs exhibit rapid response and reduced degradation due to energy downconversion facilitated by effective coupling of UV-sensitive chromophores to lanthanide luminescent centers, enhancing the spectral response range of the composite films. Furthermore, the characteristic changes of precursor particle sizes suggest formation of Tb-cpon adducts as intermediate products, leading to enhanced crystallinity and reduced defect concentrations in the Tb-cpon-perovskite hybrid film. Accordingly, the Tb-cpon-modified PSC devices obtain a champion efficiency up to 23.72% as well as a sensitive photovoltaic conversion even under pure UV irradiation. Moreover, the unencapsulated devices maintain more than 80% of the initial efficiency after continuous irradiation under a 310 nm UV lamp for 24 h (from the Au electrode side), compared to 21% for the control devices.

Recent Advances in Multifunctional Reticular Framework Nanoparticles: A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks (POFs) have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials, both in their pristine state and when subjected to various chemical and structural modifications. Metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties, such as high crystallinity, intrinsic porosity, unique structural regularity, diverse functionality, design flexibility, and outstanding stability. This review provides an overview of the state-of-the-art research on base-stable POFs, emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials. Thereafter, the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements. It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

MOF-Assisted Annealing-Free Crystallization Technology of Perovskites toward Efficient and Stable Perovskite Solar Cells

Although annealing is a commonly used crystallization method for perovskite films in perovskite solar cells (PSCs), the high thermal energy consumption and limitations on flexible devices hinder their further industrial application. We herein propose an annealing-free crystallization technology for perovskite films, assisted by the Zr-metal-organic framework (MOF) interface between SnO₂ and the perovskite. It is found that the Zr-MOF interface can accelerate the formation of perovskite intermediates and promote their conversion into perovskite crystals even without annealing. The trap density thus decreases by about one fold, accompanied by significant increases in electron and hole mobilities, resulting in enhanced carrier extraction and suppressed charge recombination. Therefore, the Zr-MOF-based PSC attains a power convention efficiency (PCE) of 20.24%, 2.2 times that (9.26%) of the pristine PSC. Furthermore, the Zr-MOF interface layer can significantly improve the air and thermal stabilities of PSCs. The Zr-MOF-based PSC exhibits 93% of its initial PCE versus 52% for the pristine PSC after 1018 h of storage in air. Additionally, after 360 h of continuous heating at 65 °C, the Zr-MOF-based PSC retains 91% of its initial PCE against 44% for the pristine PSC.

Multilateral Passivation Strategy in Post-Synthetic Flexible Metal-Organic Frameworks for Enhancing Perovskite Solar Cells

The photovoltaic performance of perovskite solar cells is severely limited by the innate defects of perovskite films. Metal-organic framework (MOF)-based additives with luxuriant skeleton structures and tailored functional groups show a huge potential to solve these problems. Here, a multilateral passivation strategy is performed by introducing two alkyl-sulfonic acid functionalized MOFs, MIL-88B-1,3-SO₃H and MIL-88B-1,4-SO₃H, respectively, obtained from MIL-88B-NH₂ through a post-synthetic process, for coordinating the lead defects and inhibiting non-radiative recombination. The flexible MIL-88B-type frameworks endow both functionalized MOFs with excellent electrical conductivity and preferable carrier transport in the hole-transport materials. Compared with the original MIL-88B-NH₂ and MIL-88B-1,4-SO₃H, MIL-88B-1,3-SO₃H exhibits optimal steric hindrance and multiple passivation groups (-NH₂, -NH-, and -SO₃H), achieving the champion doped device with an enhanced power conversion efficiency (PCE) of 22.44% and excellent stability, which maintains 92.8% of the original PCE under ambient conditions (40% humidity and 25 °C) for 1200 h.

High-performance electrochemiluminescence sensors based on ultra-stable perovskite quantum dots@ZIF-8 composites for aflatoxin B1 monitoring in corn samples

Aflatoxin B1 (AFB1) that is prone to contaminate corns brings a serious threat to human health. Therefore, it is of great significance to construct novel detection methods for AFB1 tracing. Here, methylamine perovskite quantum dots (MP QDs) encapsulated by ZIF-8 metal-organic frameworks (MP QDs@ZIF-8) were prepared and then ultra-stable electrochemiluminescence (ECL) sensors were developed. By the confinement of cavities structure, multiple MP QDs were crystallized and embedded inside ZIF-8 to form MP QDs@ZIF-8, achieving stable and robust ECL responds in aqueous environment. Further combined with AFB1-imprinted polymer, the constructed ECL sensor showed good selectivity and ultra-sensitivity (the detection limit was 3.5 fg/mL, S/N = 3) with a wide linear range from 11.55 fg/mL to 20 ng/mL for AFB1 quantification. Satisfactory recoveries in corn samples indicated the reliable practicability of the proposed sensor for AFB1 assay. This work provided a novel pathway in designing high-performance ECL sensing platform for food safety.

Regulating Crystallization and Lead Leakage of Perovskite Solar Cell Via Novel Polyoxometalate-Based Metal-Organic Framework

Despite the unprecedented progress in lead-based perovskite solar cells (PSCs), the toxicity and leakage of lead from degraded PSCs triggered by deep-level defects and poor crystallization quality increase environmental risk and become a critical challenge for eco-friendly PSCs. Here, a novel 2D polyoxometalate (POM)-based metal-organic framework (MOF) (C₅ NH₅ )₄ (C₃ N₂ H₅ )₂ Zn₃ (H₈ P₄ Mo₆ O₃₁ )₂ ·2H₂ O (POMOF) is ingeniously devised to address these issues. Note that the integration of POM endows POMOF with great advantages of electrical conductivity and charge mobility. Ordered POMOF induces the crystallization of high-quality perovskite film and eliminates lead-based defects to improve internal stability. The resultant PSCs achieve a superior power conversion efficiency (23.3%) accompanied by improved stability that maintains ≈90% of its original efficiency after 1600 h. Meanwhile, POMOF with phosphate groups effectively prevents lead leakage through in situ chemical anchoring and adsorption methods to reduce environmental risk. This work provides an effective strategy to minimize lead-based defects and leakage in sustainable PSCs through multi-functional POM-based MOF material.

Metal-Organic Framework Materials in Perovskite Solar Cells: Recent Advancements and Perspectives

Organic-inorganic hybrid perovskite solar cells (PSCs) are among the most promising candidates for the next generation of photovoltaic devices because of the significant increase in their power conversion efficiency (PCE) from less than 10% to 25.7% in past decade. The metal-organic framework (MOF) materials owing to their unique properties, such as large specific surface area, abundant binding sites, adjustable nanostructures, and synergistic effects, are used as additives or functional layers to enhance the device performance and long-term stability of PSCs. This review focuses on the recent advancements in the applications of MOFs as/in different functional layers of PSCs. The photovoltaic performance, impact, and advantages of MOF materials integrated into the perovskite absorber, electron transport layer, hole transport layer, and interfacial layer are reviewed. In addition, the applicability of MOFs to mitigate leakage of Pb²⁺ from halide perovskites and corresponding devices is discussed. This review concludes with the perspectives on further research directions for employing MOFs in PSCs.

The Stability of Hybrid Perovskites with UiO-66 Metal-Organic Framework Additives with Heat, Light, and Humidity

This study is devoted to investigating the stability of metal-organic framework (MOF)-hybrid perovskites consisting of CH3NH3PbI3 (MAPbI3) and UiO-66 without a functional group and UiO-66 with different COOH, NH2,and F functional groups under external influences including heat, light, and humidity. By conducting crystallinity, optical, and X-ray photoelectron spectra (XPS) measurements after long-term aging, all of the prepared MAPbI3@UiO-66 nanocomposites (with pristine UiO-66 or UiO-66 with additional functional groups) were stable to light soaking and a relative humidity (RH) of 50%. Moreover, the UiO-66 and UiO-66-(F)4 hybrid perovskite films possessed a higher heat tolerance than the other two UiO-66 with the additional functional groups of NH2 and COOH. Tthe MAPbI3@UiO-66-(F)4 delivered the highest stability and improved optical properties after aging. This study provides a deeper understanding of the impact of the structure of hybrid MOFs on the stability of the composite films.

Complexing Eu3+/Tb3+ in a Nanoscale Postmodified Zr-MOF toward Temperature-Modulated Multispectrum Chromism

In recent years, extensive research has been directed toward the successful preparation of nanoscale luminescent thermometers with high sensitivities operative in a broad temperature range. To achieve this goal, we have devised a unique design and facile multistep synthesis of Zr-ctpy-NMOF@Tb_xEu_y compounds by confining Ln-complexes (Ln = Eu³⁺/Tb³⁺) into a robust nanoscale Zr-NMOF (MOF-808) via postsynthetic modification. Covalent grafting of 4-(4'-carboxyphenyl)-2,2':6,2″terpyridine ligand (ctpy) with a high triplet state energy and corresponding immobilization of bimetallic Ln³⁺ ions resulted in yellow light-emitting Zr-ctpy-NMOF@Tb_1.66Eu_0.14 to achieve a sensitivity of 5.2% K^-1 (thermal uncertainty dT < 1 K) operative over a broad temperature range of 25-400 K. To defeat the odds related to the detection of minute temperature changes using luminescent materials, we prepared a white light-emitting Zr-ctpy-NMOF@Tb_1.4Eu_0.31 that showed temperature-modulated multispectrum chromism where the color drastically changes from green (at 25 K, Q.Y.: 20.21%) to yellowish-green (at 200 K, Q.Y.: 23.13%) to white (at 300 K, Q.Y.: 26.4%) to orange (at 350 K, Q.Y.: 26.93%) and finally red (at 400 K, Q.Y.: 28.2%) with a high energy transfer efficiency of 49.8%, which is further supported by electron-phonon coupling.

Fast Charge Transfer and High Stability via Hybridization of Hygroscopic Cu-BTC Metal-Organic Framework Nanocrystals with a Light-Absorbing Layer for Perovskite Solar Cells

Perovskite solar cells (PSCs) have great potential as an efficient solar energy harvesting system due to their outstanding optoelectronic properties, but the charge accumulation and recombination, as well as the moisture-induced degradation of the light-absorbing perovskite layers, remain great bottlenecks in practical applications for future technology. As a solution to this challenge, here we report a strategy to realize moisture-stable PSCs allowing fast charge transfer that, in turn, leads to high power conversion efficiency (PCE). Hybridization of hygroscopic copper(II) benzene-1,3,5-tricarboxylate metal-organic frameworks (Cu-BTC MOFs) with a light-absorbing perovskite layer for PSCs, where a moderate level of moisture attracted by Cu-BTC MOFs during the synthesis step, leads to enhanced perovskite crystallization. Besides, the perovskite-MOF hybrid facilitates the transfer of photoexcited electrons from the perovskite to TiO₂ by providing additional channels for electron extraction. This enables a high PCE of 20.5% in a triple-cation perovskite-MOF device with negligible hysteresis compared to reference devices. Moreover, the perovskite-MOF hybrid exhibits high stability in ambient air under dark conditions over a long period (up to 22 months), while the unmodified counterpart quickly decomposes into PbI₂. Consequently, this work provides a promising clue to realizeing fast charge transfer and high stability for high-performance PSCs.

Pt-embodiment ZIF-67-derived nanocage as enhanced immunoassay for infectious virus detection

A facile and general strategy has been employed to develop highly-active nanozyme for immunoassay purposes. The hollow nanostructure of the Co₃O₄ nanocages (NCs) was anchoring the platinum nanoparticles (PtNPs) enclosed by the exposed oxides framework nd formed PtNPs@Co₃O₄ NCs. The embodiment of PtNPs was considered an ideal hybrid nanozyme that efficiently catalyzed the oxidation of the substrate molecules with enhanced activity. The PtNPs@Co₃O₄ NCs were revisited and repurposed on showing its nanozyme's activity with optimization done for the immunoassay platform. The embodiment of 32.44% Pt in the hollow nanostructures demonstrated the highest signal-to-noise responses in the immunoassay. In addition, the stepwise analysis highlighted the enhancement factor of the nanocages' catalytic mechanism. Based on their catalytic activity, these nanocages have been demonstrated to enable sub-femtogram level biosensing of norovirus-like particles (NoV-LPs) with highly selective signals in the capture-detect immunoassay format. The detection limit of the prepared immunoassay achieved 33.52 viral NoV copies/mL of the detection limit, which is 321-folds lower magnitude of the commercial ELISA. This nanocage's enhanced synergic catalytic properties could have great potential applications, including catalysis, biological labeling, and bioassays.

Reticular Nanoscience: Bottom-Up Assembly Nanotechnology

The chemistry of metal-organic and covalent organic frameworks (MOFs and COFs) is perhaps the most diverse and inclusive among the chemical sciences, and yet it can be radically expanded by blending it with nanotechnology. The result is reticular nanoscience, an area of reticular chemistry that has an immense potential in virtually any technological field. In this perspective, we explore the extension of such an interdisciplinary reach by surveying the explored and unexplored possibilities that framework nanoparticles can offer. We localize these unique nanosized reticular materials at the juncture between the molecular and the macroscopic worlds, and describe the resulting synthetic and analytical chemistry, which is fundamentally different from conventional frameworks. Such differences are mirrored in the properties that reticular nanoparticles exhibit, which we described while referring to the present state-of-the-art and future promising applications in medicine, catalysis, energy-related applications, and sensors. Finally, the bottom-up approach of reticular nanoscience, inspired by nature, is brought to its full extension by introducing the concept of augmented reticular chemistry. Its approach departs from a single-particle scale to reach higher mesoscopic and even macroscopic dimensions, where framework nanoparticles become building units themselves and the resulting supermaterials approach new levels of sophistication of structures and properties.

Confinement of all-inorganic perovskite quantum dots assembled in metal-organic frameworks for ultrafast scintillator application

Nucleation and growth of quantum dots (QDs) are thermodynamic processes driven by the total Gibbs free energy change (ΔG). We discuss the nucleation and growth theory of perovskite quantum dots (PeQDs) inside a metal-organic framework (MOF) as a strong constraint framework, which can effectively confine the size of QDs below 3 nm and achieve a scintillator with an ultra-fast transient lifetime of fluorescence. Therefore, based on the requirements for the optical properties of ultra-fast scintillation materials, two kinds of suitable MOFs (UiO-67-bpy and MIL-101(Cr)) were selected for synthesis. The method of 'ship-in-bottle' was adopted to embed perovskite quantum dots CsPbBrCl₂ into MOF cages to form PeQDs@MOF composite materials, which is different from the one-pot method. In order to further improve the stability of PeQDs@MOF, polystyrene was used to cure the composite scintillator, which can resist exposure to UV light and withstand the ISO level 4 test, with the fastest transient lifetime of 2.13 ns and a fluorescence emission wavelength of 445 nm.

Enhancing the Performance of Quasi-2D Perovskite Light-Emitting Diodes Using Natural Cyclic Molecules with Distinct Phase Regulation Behaviors

In this study, two natural small molecules, α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD), are used as additives to improve the performance of quasi-2D PEA₂Cs_n-1Pb_nBr_3n+1 (n = 3, herein) PeLEDs. Both of them are shown to efficiently passivate the quasi-2D perovskite films to afford improved film quality and morphology, but they exhibit distinct phase regulation behaviors possibly due to their different pore sizes. It reveals that α-CD effectively suppresses the formation of the low-n phases (n ≤ 2), while β-CD better regulates the phase with a medium-n value (n = 3). Because of effectively suppressing the formation of low-n phases, the CD-assisted quasi-2D perovskite films possess facilitated exciton energy transfer and reduced nonradiative recombination. Consequently, the optimized α-CD-derived PeLED shows the highest luminance (L_max) of 37,825 cd/m² with an external quantum efficiency (EQE) of 3.81%, while the β-CD-derived PeLED delivers a lower L_max of 24,793 cd/m² with an EQE of 3.09%. Compared to the pristine device, L_max is enhanced by 6.3 and 3.8 times for α-CD- and β-CD-based PeLEDs, respectively, and EQE is enhanced by ∼4.8 times for both devices; besides, both CD-assisted devices also exhibit improved color purity and a lower bias dependency of electroluminescent intensity.

Tailoring biocompatibility of composite scaffolds of collagen/guar gum with metal-organic frameworks

Metal-organic frameworks (MOFs) are microporous materials with high potential for biomedical applications. They are useful as drug delivery systems, antibacterials, and biosensors. Recently, composite materials comprised of polymer matrixes and MOFs have gained relevance in the biomedical field due to their high potential as materials to accelerate wound healing. In this work, we studied the potential applications of composite hydrogels containing MgMOF74, CaMOF74, and Zn(Atz)(Py). The composite hydrogels are biodegradable, being completely degraded after 15 days by the action of collagenase and papain. The composites showed high biocompatibility reaching cell viabilities up to 165.3 ± 8.6% and 112.3 ± 12.8% for porcine fibroblasts and human monocytes, respectively. The composites did not show hemolytic character and they showed antibacterial activity against Escherichia coli reaching up to 84 ± 5% of inhibition compared with amoxicillin (20 ppm). Further, the immunological assays revealed that the composites produce a favorable cell signaling stimulating the secretion of the TGF-β and MCP-1 cytokines and maintaining the secretion of TNF-α in normal levels. Finally, the composites showed potential to be used as controlled drug delivery systems reaching a release efficiency of 30.5 ± 2.5% for ketorolac. Finally, results revealed that ColGG-Zn(Atz)(Py) was the best formulation evaluated.

Amin M, Kaneti Y, Suendo V. Role of Urea on Structural, Textural, and Optical Properties of Macroemulsion-assisted Synthesized Holey ZnO Nanosheets for Photocatalytic Applications

Using a macroemulsion-assisted solvothermal method, the present study produces holey ZnO nanosheets exhibiting the hexagonal wurtzite crystal structure. In the synthetic process, urea is employed as a hydrolyzing agent. Its...

Introducing Postmetalation Metal-Organic Framework to Control Perovskite Crystal Growth for Efficient Perovskite Solar Cells

A novel lead-containing metal-organic framework (Pb-MOF) is synthesized through postmetalation of MOF-525. Postmetalation renders lead ions bound with the organic linker of MOF-525, which can serve as nucleation points to promote perovskite crystallization. The introduction of lead postmetalated MOF-525 (Pb-MOF) as a scaffold layer between compact TiO₂ (c-TiO₂) layer and perovskite layer promotes perovskite crystal growth in enlarging crystal grain size with better crystallinity, hence decreasing defect sites in the perovskite layer. Postmetalation of MOF-525 with lead ions allows MAPbI₃ to form a solid crystal structure to facilitate the charge separation between electron transport layer (ETL) and light-harvesting layer so as to resolve the issue of possible vacancies present in MOFs. As a result, the champion perovskite solar cell (PSC) with the introduction of Pb-MOF exhibits a power conversion efficiency (PCE) of 20.87% and better stability (86% PCE retention after 40 days), outperforming the pristine PSC (16.85% PCE, with 52% retention after 40 days) and MOF-525-introduced PSC (18.61% PCE, with 76% retention after 40 days).

Pollutant degradation with mediator Z-scheme heterojunction photocatalyst in water: A review

The Z-scheme heterojunction is a photocatalyst with narrow band gap and sufficiently high oxidization and reduction powers for degradation of pollutants in waters. This review firstly summarizes the fundamentals of photocatalysis, and explains the need to develop Z-scheme heterojunctions to harvest energy from sunlight effectively. Secondly, contemporary reports of degradation wastewater pollutants, including organic dyes, antibiotics, and other chemicals are reviewed and discussed. A challenge in the selection of an appropriate Z-scheme for removing a specific pollutant is the lack of available energy levels that are offered by the catalyst and the lack of redox energy levels that are required to break down essential chemical bonds of the pollutants. With reference to the redox energy levels offered by the active photocatalytic species, the redox energy levels of specific pollutants studied in literature are estimated. Challenges and prospects concerning the use of the Z-scheme to degrade recalcitrant pollutants under irradiation by sunlight are outlined at the end of this review.

Synergistic Effects of Eu-MOF on Perovskite Solar Cells with Improved Stability

Enhancing device lifetime is one of the essential challenges in perovskite solar cells. The ultrathin Eu-MOF layer is introduced at the interface between the electron-transport layer and the perovskite absorber to improve the device stability. Both Eu ions and organic ligands in the MOF can reduce the defect concentration and improve carrier transport. Moreover, due to the Förster resonance energy transfer effect, Eu-MOF in perovskite films can improve light utilization and reduce the decomposition under ultraviolet light. Meanwhile, Eu-MOF also turns tensile strain to compressive strain in the perovskite films. As a result, the corresponding devices achieve a champion power conversion efficiency (PCE) of 22.16%. In addition, the devices retain 96% of their original PCE after 2000 h under the relative humidity of 30% and 91% of their original PCE after 1200 h after continuous 85 °C aging condition in N₂ .

MOFs based on the application and challenges of perovskite solar cells

In recent years, perovskite solar cells (PSCs) have attracted much attention because of their high energy conversion efficiency, low cost, and simple preparation process. Up to now, the photoelectric conversion efficiency of solar cells has been increased from 3.8% to 25.5%. Metal–organic skeleton-derived metal oxides and their composites (MOFs) are widely considered for application in PSCs due to their low and flat charge/discharge potential plateau, high capacity, and stable cycling performance. By combining MOFs and PSCs, based on the composition materials of perovskite film, electron transport layer, hole transport layer, and interfacial interlayer of PSCs, this article discusses the photovoltaic performance or structure optimization effect of MOFs in each function layer, which is of great significance to improve the photovoltaic performance of the cell. The problems faced by MOFs on perovskite solar cells are summarized, the next research directions are discussed, and the development of this crossover area of MOFs–PSC is foreseen to accelerate the comprehensive research and popularization of MOFs on PSCs.

Present and Perspectives of Photoactive Porous Composites Based on Semiconductor Nanocrystals and Metal-Organic Frameworks

This review focuses on the recent developments in synthesis, properties, and applications of a relatively new family of photoactive porous composites, integrated by metal halide perovskite (MHP) nanocrystals and metal-organic frameworks (MOFs). The synergy between the two systems has led to materials (MHP@MOF composites) with new functionalities along with improved properties and phase stability, thus broadening their applications in multiple areas of research such as sensing, light-harvesting solar cells, light-emitting device technology, encryption, and photocatalysis. The state of the art, recent progress, and most promising routes for future research on these photoactive porous composites are presented in the end.

Correlating the Active Layer Structure and Composition with the Device Performance and Lifetime of Amino-Acid-Modified Perovskite Solar Cells

Additive engineering is emerging as a powerful strategy to further enhance the performance of perovskite solar cells (PSCs), with the incorporation of bulky cations and amino acid (AA) derivatives being shown as a promising strategy for enhanced device stability. However, the incorporation of such additives typically results in photocurrent losses owing to their saturated carbon backbones, hindering charge transport and collection. Here, we investigate the use of AAs with varying carbon chain lengths as zwitterionic additives to enhance the PSC device stability, in air and nitrogen, under illumination. We, however, discovered that the device stability is insensitive to the chain length as the anticipated photocurrent drops as the chain length increases. Using glycine as an additive results in an improvement in the open circuit voltage from 1.10 to 1.14 V and a resulting power conversion efficiency of 20.2% (20.1% stabilized). Using time-of-flight secondary ion mass spectrometry, we confirm that the AAs reside at the surfaces and interfaces of our perovskite films and propose the mechanisms by which stability is enhanced. We highlight this with glycine as an additive, whereby an 8-fold increase in the device lifetime in ambient air at 1 sun illumination is recorded. Short-circuit photoluminescence quenching of complete devices is reported, which reveals that the loss in photocurrent density observed with longer carbon chain AAs results from the inefficient charge extraction from the perovskite absorber layer. These combined results demonstrate new fundamental understandings about the photophysical processes of additive engineering using AAs and provide a significant step forward in improving the stability of high-performance PSCs.

Extinction Coefficient Modulation of MoO3 Films Doped with Plasmonic Nanoparticles: From an Effective Medium Theory Description

This work focused on the application of the effective medium theory to describe the extinction coefficient (Qext) in molybdenum trioxide (MoO3) doped with different kinds of plasmonic nanoparticles, such as silver (Ag), gold (Au), and copper (Cu). Usually, in studies of these materials, it is normal to analyze the transmission or absorption spectra. However, the effect of this type or size of nanoparticles on the spectra is not as remarkable as the effect that is found by analyzing the Qext of MoO3. It was shown that the β-phase of MoO3 enhanced the intensity response of the Qext when compared to the α-phase of MoO3. With a nanoparticle size of 5 nm, the Ag-doped MoO3 was the configuration that presents the best response in Qext. On the other hand, Cu nanoparticles with a radius of 20 nm embedded in MoO3 was the configuration that presented intensities in Qext similar to the cases of Au and Ag nanoparticles. Therefore, implementing the effective medium theory can serve as a guide for experimental researchers for the application of these materials as an absorbing layer in photovoltaic cells.

Mitigation of vacancy with ammonium salt-trapped ZIF-8 capsules for stable perovskite solar cells through simultaneous compensation and loss inhibition

Due to the easy loss of ions during synthesis or usage, vacancies in perovskite film are ubiquitous, accelerating the degradation of perovskite materials and seriously hampering the stability of perovskite solar cells (PSCs). Herein, to simultaneously compensate for vacancies and reduce ammonium cation loss, a sustained release strategy was proposed by introducing multi-functional capsules consisting of zeolitic imidazolate framework-8 (ZIF-8) encapsulation agent and ammonium iodide salts as interlayer between the perovskite and hole transport layer. In the capsule interlayer, not only are ammonium iodide salts in ZIF-8 pores released to the perovskite layer, compensating for the vacancies, but the ZIF-8 also prevents the organic component of perovskite from evaporating and isolates the perovskite from moisture. As a consequence, decreased trap density, improved device efficiency, and enhanced stability of PSCs are obtained owing to the successful passivation of defects by the introduced capsules. ZIF-8@FAI shows the highest efficiency of 19.13% and a stabilized PCE over 93% of the initial efficiency at maximum power point for 150 h. This work provides a new strategy to improve efficiency and stability of PSCs based on the large family of porous materials.

Nanoscale cobalt-based metal-organic framework impairs learning and memory ability without noticeable general toxicity: First in vivo evidence

Metal-organic frameworks (MOFs) exhibit broad potential applications in the environmental, biomedical, catalyst, and energy fields. However, the currently existing data hardly shed light on their health risks before the MOFs' large-scale usage. In this context, we exploratively investigated the in vivo fate and effect of one representative cobalt-based zeolitic imidazolate framework (ZIF-67) at the nano- (60 nm) and submicron- (890 nm) scales. Different from submicron-scale ZIF-67 showing better biosafety, nanoscale particles manifested a neurodegenerative risk at the dose of no general toxicity, evidenced by the impairment of learning and memory ability and disordered function of the neuropeptide signaling pathway in a rat model. The involvement of oxidative damage and inflammatory processes in the neurotoxicity induced by ZIF-67 was discussed as well. These findings not only provide a wake-up call for the prudent applications of MOFs but also provide insight into the better design and safer use of MOFs for broader applications.

New Insight into the Lewis Basic Sites in Metal-Organic Framework-Doped Hole Transport Materials for Efficient and Stable Perovskite Solar Cells

Currently, Spiro-OMeTAD is the most widely used hole transport material (HTM) in the best-performing perovskite solar cells (PSCs), resulting from its suitable energy level and facile processing. However, the intrinsic properties of organic molecules, such as low conductivity and a nonpolar contact interface, will limit the power conversion efficiency (PCE) and stability of Spiro-OMeTAD-based PSCs. Chemical doping could be an effective strategy to ameliorate the performance of Spiro-OMeTAD, and most of the dopants are designed for controllably oxidizing Spiro-OMeTAD. In this work, a highly stable metal-organic framework {[Zn(Hcbob)]·(solvent)}_n (Zn-CBOB) with rod topology and Lewis basic sites is assembled and employed as a dopant for the hole transport layer. It is found that Zn-CBOB not only controllably oxidizes Spiro-OMeTAD and improves the conductivity of the HTM but also passivates the surface traps of the perovskite film by coordinating with Pb²⁺. The Zn-CBOB-doped PSCs achieved a remarkable PCE of 20.64%. In addition, the hydrophobicity of Zn-CBOB can prevent water from destroying the perovskite layer, which helps elevate the stability of PSCs.