Controllable Synthesis of Porphyrin‐Based 2D Lanthanide Metal–Organic Frameworks with Thickness‐ and Metal‐Node‐Dependent Photocatalytic Performance

Materials for Electrocatalysis: Future Prospects in Energy Conversion

Electrocatalysts play a pivotal role in various energy conversion processes, such as water splitting, batteries, carbon dioxide reduction, and fuel cell reactions, by significantly reducing the energy barrier and enhancing reaction kinetics. This review highlights the potential of earth-abundant electrocatalysts, with a particular focus on their capabilities in critical electrochemical reactions, including oxygen evolution reaction, carbon dioxide reduction reaction, oxygen reduction reaction and hydrogen evolution reaction. Emphasis is also placed on bifunctional, trifunctional, and tetrafunctional performance, showcasing their adaptability and effectiveness across diverse energy applications. Exploration is done on a range of promising materials, including transition metal chalcogenides, MXenes, metal-organic frameworks, covalent organic frameworks, and layered double hydroxides. By examining their intrinsic properties, structural versatility, and surface engineering strategies, this review sheds light on the factors that govern their catalytic efficiency and stability. The integration of experimental advancements with theoretical insights provides a deeper understanding of mechanisms driving their catalytic activity. Additionally, we address the scalability, cost-effectiveness, and environmental impact of these materials, underlining their potential for large-scale deployment. By synthesizing recent progress and identifying challenges, this work delivers a roadmap for the model and application of multifunctional electrocatalysts, fostering innovations that align with the goals of sustainable energy systems.

Sunlight-Driven Photocatalysis for a Set of 3D Metal-Porphyrin Frameworks Based on a Planar Tetracarboxylic Ligand and Lanthanide Ions

Metal-porphyrin frameworks (MPFs) with trivalent lanthanide ions are the most sought-after materials in the past decade. Their porosities are usually complemented by optical properties imparted by the metal nodes, making them attractive multifunctional materials. Here, we report a novel family of 3D MPFs obtained through solvothermal reactions between tetrakis(4-carboxyphenyl) porphyrin (H4TCPP) and different lanthanide sources, yielding an isostructural family of compounds along the lanthanide series: [Ln2(DMF)(TCPP)1.5] for Ln = La, Ce, Nd, Pr, Er, Y, Tb, Dy, Sm, Eu, Gd, and Tm. Photoluminescent properties of selected phases were explored at room temperature. Also, the photocatalytic performance exhibited by these compounds under sunlight exposure is promising for its implementation in organic pollutant degradation. In order to study the photocatalytic activity of Ln-TCPPs in an aqueous medium, methylene blue (MB) was used as a contaminant model. The efficiency for MB degradation was Sm > Y > Yb > Gd > Er > Eu > either no catalyst or no light, obtaining more than 70% degradation at 120 min with Sm-TCPP. These results open the possibility of using these compounds in optical and optoelectronic devices for water remediation and sensing.

A metal-organic framework complex for enhancing tumor treatments through synergistic effect of chemotherapy and photodynamic therapy

Porphyrin-based metal-organic frameworks (PMOFs) are a kind of crystal hybrid material with broad application prospects in energy, catalysis, biomedicine, and other fields. In this study, the La-TCPP PMOF nanocrystal was constructed using a porphyrin ligand and La ion. This material can produce a high loading rate on doxorubicin (DOX) owing to its special porous structure. The high loading rate of drug molecules and the reactive oxygen species (ROS) of the porphyrin ligand enable La-TCPP@DOX nanocrystal to produce a powerful killing effect on cancer cells under the synergistic attack of chemotherapy (CT) and photodynamic therapy (PDT). Finally, by modifying the targeted aptamer, the actual therapeutic effect of this special La-TCPP@DOX@Apt material on tumors was confirmed by applying the established mouse tumor model. The composite nanomaterial not only avoids the side effects caused by high concentrations of chemotherapeutic drugs, but also overcomes the limitation of PDT owing to insufficient light penetration and can inhibit and kill solid tumors under the condition of synergistic attack. This study is a complement to PMOF crystal materials, and its tumor-killing ability was achieved by loading drugs and introducing targeting molecules, which proves that the synergistic attack can more effectively inhibit and treat solid tumors. These studies have a reference and guiding significance for the treatment of cancer patients.

Inner transition metal-modulated metal organic frameworks (IT-MOFs) and their derived nanomaterials: a strategic approach towards stupendous photocatalysis

Photocatalysis, as an amenable and effective process, can be adopted for pollution remediation and to alleviate the ongoing energy crisis. In this case, recently, metal organic frameworks (MOFs) have attracted increasing attention in the field of photocatalysis owning to their unique characteristics including large specific surface area, tuneable pore architecture, mouldable framework composition, tuneable band structure, and exceptional photon absorption tendency complimented with superior anti-recombination of excitons. Among the plethora of frameworks, inner transition metal based-MOFs (IT-MOFs) have started to garner significant traction as photocatalysts due to their distinct characteristics compared to conventional transition metal-based frameworks. Typically, IT-MOFs have the tendency to generate high nuclearity clusters and possess abundant Lewis acidic sites, together with mixed valency, which aids in easily converting redox couples, thereby making them a suitable candidate for various photocatalytic reactions. Therefore, in this contribution, we aim to summarise the excellent photocatalytic performance of IT-MOFs and their composites accompanied by a thorough discussion of their topological changes with a variation in the structure of the metal cluster, fabrication routes, morphological features, and physico-chemical properties together with a brief discussion of computational findings. Moreover, we attempt to explore the scientific understanding of the functionalities of IT-MOFs and their composites with detailed mechanistic pathways for in-depth clarity towards photocatalysis. Furthermore, we present a comprehensive analysis of IT-MOFs for various crucial photocatalytic applications such as H₂/O₂ evolution, organic pollutant degradation, organic transformation, and N₂ and CO₂ reduction. In addition, we discuss the measures employed to enhance their performance with some future directions to address the challenges with IT-MOF-based nanomaterials.

Highly Sensitive Photoelectrochemical Immunosensor Based on Organic Multielectron Donor Nanocomposite as Signal Probe

Organic photoelectric materials with conjugated electron-rich structures and good biocompatibilities have broad application prospects in biosensors. Herein, we report a promising organic photoelectric multielectron donor nanocomposite for highly sensitive PEC immunoassays. Specifically, the organic multielectron donor nanocomposite (DA-ZnTCPP-g-C₃N₄) was prepared from dopamine (DA, polyphenol hydroxyl structure substance), zinc tetracarboxylate porphyrin (ZnTCPP, large p-π conjugated heterocyclic compound), and two-dimensional graphene-like nitrogen carbide (g-C₃N₄) via an amidation reaction. With a multielectron donor structure and photoelectricity, this nanocomposite can achieve sensitization by self-structure without the addition of an electron donor in the test solution. It was utilized to label the carcinoembryonic detection antibody as a immuno-probe (Ab2-DA-ZnTCPP-g-C₃N₄). Meanwhile, the glassy carbon electrode electrodeposited with gold nanoparticles anchoring the capture antibody was used as a PEC immunomatrix (Ab1/DpAu/GCE). The enhanced PEC current, "signal on", was confirmed by the immunosensor via sandwich immunorecognition of a carcinoembryonic antigen (CEA). Under optimal conditions, the as-prepared sensing platform displayed high sensitivity for CEA with a dynamic linear response range from 10 fg·mL^-1 to 1 mg·mL^-1 and a lower detection limit of 3.6 fg·mL^-1. This organic nanocomposite showed good sensitivity and stability in an immunosensing system with a low background. This strategy affords a promising approach for biological applications of organic photoelectric materials.

Microwave- and ultrasonic-assisted synthesis of 2D La-based MOF nanosheets by coordinative unsaturation degree to boost phosphate adsorption

The metal or metal clusters and organic ligands are relevant to the selectivity and performance of phosphate removal in MOFs, and the electron structure, chemical characteristics, and preparation method also affect efficiency and commercial promotion. However, few reports focus on the above, especially for 2D MOF nanomaterials. In this work, two 2D Ln-TDA (Ln = La, Ce) nanosheets assembled via microwave- and ultrasonic-assisted methods are employed as adsorbents for phosphate (H2PO4 -, HPO4 2-) removal for the first time. Their microstructure and performance were characterized using XRD, TEM, SEM, AFM, FTIR, zeta potential, and DFT calculations. The prepared 2D Ln-TDA (Ln = La, Ce) nanosheets exposed more adsorption sites and effectively reduced the restrictions of mass transfer. Based on this, the Langmuir model was employed to estimate the maximum adsorption capacities of the two kinds of nanosheets, which reached 253.5 mg g-1 and 259.5 mg g-1, which are 553 times and 3054 times larger than those for bulk Ln-TDA (Ln = La, Ce), respectively. Additionally, the kinetic data showed that the adsorption equilibrium time is fast, approximately 15 min by the pseudo-second-order model. In addition, the prepared products not only have a wide application range (pH = 3-9) but also offer eco-safety in terms of residuals (no Ln leak out). Based on the XPS spectra, FTIR spectra and DFT calculations, the main adsorption mechanisms included ligand exchange and electrostatic interactions. This new insight provides a novel strategy to prepare 2D MOF adsorbents, achieving a more eco-friendly method (microwave- and ultrasonic-assisted synthesis) for preparing 2D Ln-based MOF nanosheets by coordinative unsaturation to boost phosphate adsorption.

The use of metal-organic frameworks as heterogeneous catalysts

This article presents an overview of some of the available research studies of MOFs as catalysts. Catalytic studies of magnetic iron oxide nanoparticles with modified surfaces, MOFs with precious metals such as palladium, platinum, and silver, with zirconium, hafnium, copper, alkaline earth metals, lanthanides are generalized. The studies of the catalytic activity of micro- and mesoporous MOF structures are described.

Imparting Multifunctionality in Zr-MOFs Using the One-Pot Mixed-Linker Strategy: The Effect of Linker Environment and Enhanced Pollutant Removal

The development of mixed-linker metal-organic frameworks (MOFs) is an efficient strategy to improve the performance of MOFs. Herein, we successfully integrate tetrakis(4-carboxyphenyl)porphyrin (TCPP) into different Zr-MOFs via a facile one-pot solvothermal synthesis while preserving the integrity of their frameworks. The functional groups, length of primary linkers, and the inner pore structure significantly affected the properties of the synthesized TCPP@MOFs, such as surface area, average pore size, and ¹O₂ productivity. Among them, TCPP@PCN-777 demonstrated the largest surface area (2386 cm²/g, as measured by N₂ uptake) and the highest ¹O₂ generation rate (1.15 h^-1, [¹O₂]_ss = 2.66 × 10^-12 M) under irradiation. The TCPP loading was also shown to affect the crystal phase, morphology, surface area, and photochemical properties of the synthesized MOFs. Therefore, TCPP@PCN-777s with various TCPP loadings were synthesized to investigate the optimum loading. The optimized TCPP@MOF, TCPP@PCN-777-30, was evaluated for its removal of model contaminant ranitidine (RND) through both adsorption and photodegradation. TCPP@PCN-777-30 showed a higher adsorption capacity toward RND than both the parent MOF (PCN-777) and commercially available activated carbon, and effectively degraded RND in aqueous solution (>99% photodegradation in 1 h). With irradiation, TCPP@PCN-777-30 showed a minimal loss in adsorption efficiency over four consecutive treatment cycles, confirming the reusability of the material enabled through the incorporation of TCPP into the MOF structure. This work not only developed an efficient multifunctional material for environmental remediation but also forwarded knowledge on the effect of linker environment (i.e., functional groups, framework structure, and linker ratio) on the properties of TCPP@MOFs to guide future research on mixed-linker MOFs.

Two-Dimensional Metal-Organic Framework Nanosheets: Synthesis and Applications in Electrocatalysis and Photocatalysis

Two-dimensional metal-organic nanosheets (2D MONs) are an emerging class of ultrathin, porous, and crystalline materials. The organic/inorganic hybrid nature offers MONs distinct advantages over other inorganic nanosheets in terms of diversity of organic ligands and metal notes. Compared to bulk three-dimensional metal-organic frameworks, 2D MONs possess merits of high density and readily accessible catalytic sites, reduced diffusion pathways for reactants/products, and fast electron transport. These features endow MONs with enhanced physical/chemical properties and are ideal for heterogeneous catalysis. In this Review, state-of-the-art synthetic methods for the fabrication of 2D MONs were summarized. The advances of 2D MONs-based materials for electrocatalysis and photocatalysis, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂ RR), and electro-/photocatalytic organic transformations were systematically discussed. Finally, the challenges and perspectives regarding future design and synthesis of 2D MONs for high-performance electrocatalysis and photocatalysis were provided.

Ultra-stable two-dimensional metal-organic frameworks for photocatalytic H2 production

Two-dimensional (2D) metal-organic frameworks (MOFs) are some of the most promising photocatalysts owing to their high numbers of exposed active sites and excellent charge mobility. However, the synthesis of highly stable 2D MOF photocatalysts involves challenges, and examples have been rarely reported. Herein, a new kind of material, 2D indium-based porphyrin MOF cubic nanosheets (2D In-TCPP NS) with an average thickness of ∼3.97 nm, is synthesized via a surfactant-assisted approach, and it shows good chemical stability in the pH range of 2-11 in aqueous solution. In photocatalytic H₂-generation experiments, 2D In-TCPP NS exhibits activity that is enhanced by over one order of magnitude compared with the 3D bulk In-TCPP MOF, arising from its highly enhanced electron-hole separation abilities. Moreover, after 40 h of continuous photocatalysis testing, 2D In-TCPP NS shows nearly no activity decrease, which suggests its great potential for practical commercial use.

Self-enhanced photoelectrochemical sensor based on a Schottky heterostructure organic electron donor matrix

A self-enhanced photoelectrochemical copper ions sensor was constructed using an organic electron donor matrix with a Schottky heterostructure prepared from dopamine and single walled carbon nanohorns. The determination of Cu²⁺ with no additional electron donor solution, with high sensitivity and low background, provides new inspiration for the development of photoelectric sensing.

Electrochemical dopamine sensor based on bi-metallic Co/Zn porphyrin metal-organic framework

Integrating other metal ions into mono-metallic metal-organic framework (MOF) to form bi-metallic MOF is an effective strategy to enhance the performance of MOFs from the internal structure. In this study, two-dimensional (2D) cobalt/zinc-porphyrin (Co/Zn-TCPP) MOF nanomaterials with different Co/Zn molar ratios were synthesised using a simple surfactant-assisted method, and novel dopamine (DA) sensing methods were constructed based on these materials. The characterisation results showed that all MOF with different Co/Zn molar ratios presented a nanofilm, and the Co and Zn elements were uniformly distributed. All sensors based on Co_xZn_100-x-TCPP had a certain catalytic performance to DA. Among them, the sensor based on CO₂₅Zn₇₅-TCPP showed the strongest signal response, indicating that the catalytic performance of MOF on DA can be adjusted by changing the Co/Zn molar ratio. The doping of metal ions improves the chemical environment of the pores, and increases the types and spatial arrangement of the active sites of the MOF, which is beneficial to the electron transfer and exchange with DA; Co²⁺ and Zn²⁺ active centres have a synergistic promotion effect, so the catalytic activity of MOF is significantly improved. The linear range at the potential of 0.1 V based on Co₂₅Zn₇₅-TCPP for DA was 5 nM-177.8 μM, with a detection limit of 1.67 nM (S/N = 3). The sensor exhibited a good selectivity for detecting DA. This research is expected to provide new ideas and references for constructing high-performance sensing interfaces and platforms.

An electron donor-acceptor organic photoactive composite with Schottky heterojunction induced photoelectrochemical immunoassay

A signal enhancement photoelectrochemical (PEC) immunoassay system induced by the composite (PTCs@Au) of electron donor-acceptor with Schottky heterojunction was designed. Carcinoembryonic antigen (CEA) was selected as a model target. Initially, the capture anibody (Ab1) was linked to gold nanoparticles electrodeposited on glassy carbon electrode and sealed by bovine serum albumin. Meanwhile, the organic semiconductor (PTCs) with the structure of electron donor-acceptor was synthetized from perylene tetracarboxylic dianhydride (acceptor) and dopamine (donor) via amidation reaction. Then PTCs@Au composite with Schottky heterojunction was formed through gold nanoparticles in situ reduction and functionalization with PTCs. Next, the detection antibody was labeled by PTCs@Au composite (Ab2-PTCs@Au) as an immuno-probe. The PTCs@Au was introduced via sandwich immune reaction leading to enhancement PEC signal without additional electron donor nor acceptor for achieving quantitative detection of CEA under external light. The proposed immunoelectrode showed dynamic ranges of 0.5 fg mL^-1 to 10 pg mL^-1 and 10 pg mL^-1 to 1 μg mL^-1 with the detection limit of 0.17 fg mL^-1. In addition, this PEC strategy with acceptable selectivity and stability can be potentially applied to detect other targets by choosing appropriate target recognition unit.

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

High-efficiency photocatalysis in metal-organic frameworks (MOF) and MOF nanosheets (NSs) are often limited by their short-lived charge separation as well as self-quenching. Here, we propose to use the energy-transfer process (EnT) to increase charge separation, thus enhancing the catalytic performance of a series of MOF NSs. With the use of NS, the photocatalyst can also be well isolated to reduce self-quenching. Tetrakis(4-carboxyphenyl) porphyrin (H₄ TCPP) and 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H₄ TBAPy) linkers were chosen as the acceptor and donor moieties, respectively. Accounting for the precise spatial design afforded by the MOF NSs, the donor and acceptor moieties could be closely positioned on the NSs, allowing for an efficient EnT process as well as a high degree of site isolation. Two templates, donor-on-acceptor NS and acceptor-on-donor NS catalysts, were successfully synthesized, and the results show that the second one has much enhanced catalytic performances over the first one due to site-isolated active photocatalysts.