Metal-Organic Framework-Based Catalysts with Single Metal Sites

Atomically dispersed iron sites from eco-friendly microbial mycelium as highly efficient hydrogenation catalyst

Iron, one of the most abundant elements on earth and an essential element for living organisms, plays a crucial role in our daily metabolism. In the field of catalysis, the development of high-performance catalysts based on less toxic iron element is also of significant importance for green chemistry and a sustainable future. To construct Fe-based heterogeneous catalysts with excellent hydrogenation performance, precise modulation of the atomic coordination structure is a key strategy for enhancing catalytic activity. In this study, we present an in-situ coating method for applying a zeolitic imidazolate framework (ZIF) onto the surface of fungal hyphae. The asymmetric coordination structure of Fe1-N3P1 was precisely tailored by utilizing the phosphorus source from the fungus and the nitrogen source in the ZIFs. Detailed characterizations and density functional theory calculations revealed that the incorporation of ZIFs not only increased the specific surface area of catalysts, but also facilitated the dispersion of Fe2P nanoparticles into the Fe1-N3P1 center, making the lowest reaction energy barrier and resulting in the best performance for nitrobenzene hydrogenation when compared to the Fe2P nanoparticles and clusters. This research introduces a novel design concept for constructing asymmetric monoatomic configuration based on the inherent characteristics of natural microorganisms and the exogenous porous coordination polymers.

Improving CO2 electroconversion by customizing the hydroxyl microenvironment around a semi-open Co-N2O2 configuration

Constructing local microenvironments is one of the important strategies to improve the electrocatalytic performances, such as in electrochemical CO2 reduction (ECR). However, effectively customizing these microenvironments remains a significant challenge. Herein, utilizing carbon nanotube (CNT) heterostructured semi-open Co-N2O2 catalytic configurations (Co-salophen), we have demonstrated the role of the local microenvironment on promoting ECR through regulating the location of hydroxyl groups. Concretely, compared with the maximum Faradaic efficiency (FE) of 62% for carbon monoxide (CO) presented by Co-salophen/CNT without a hydroxyl microenvironment, the designed Co-salophen-OH3/CNT, featuring hydroxyl groups at the Co-N2O2 structural opening, shows remarkable CO2-to-CO electroreduction activity across a wide potential window, with the FE of CO up to 95%. In particular, through the deuterium kinetic isotope experiments and theoretical calculations, we decoded that the hydroxyl groups act as a proton relay station, promoting the efficient transfer of protons to the Co-N2O2 active sites. The finding demonstrates a promising molecular design strategy for enhancing electrocatalysis.

Metal-Organic Frameworks with Phosphonate Monoester Linkers for Catalytic C(sp2)-H Borylation of Alkenes

An isoreticular metal-organic framework (MOF) series was constructed from nickel or cobalt nodes, phosphonate monoester, and bipyridine linkers. The cobalt-containing MOFs were found to catalyze the dehydrogenative C-H borylation of alkenes under mild conditions. This process selectively generates vinyl boronate without the formation of alkyl boronate byproducts and is insensitive to air, enabling large-scale preparation of the target products with isolated yields of over 80%.

Development of the design and synthesis of metal-organic frameworks (MOFs) - from large scale attempts, functional oriented modifications, to artificial intelligence (AI) predictions

Owing to the exceptional porous properties of metal-organic frameworks (MOFs), there has recently been a surge of interest, evidenced by a plethora of research into their design, synthesis, properties, and applications. This expanding research landscape has driven significant advancements in the precise regulation of MOF design and synthesis. Initially dominated by large-scale synthesis approaches, this field has evolved towards more targeted functional modifications. Recently, the integration of computational science, particularly through artificial intelligence predictions, has ushered in a new era of innovation, enabling more precise and efficient MOF design and synthesis methodologies. The objective of this review is to provide readers with an extensive overview of the development process of MOF design and synthesis, and to present visions for future developments.

MOFs-based adsorbents for the removal of tetracycline from water and food samples

Tetracyclines (TCs) are widely employed for the prevention and treatment of diseases in animals besides being deployed to promote animal growth and weight gain. Such practices result in trace amounts of TCs occurrence in water and foodstuffs of animal origin, including eggs and milk, thus posing severe health risks to humans. To ensure the food and water safety and to avoid exposure to humans, the removal of TC residues from food and water has recently garnered a considerable attention. Metal-organic frameworks (MOFs), endowed with unique structural and surface properties with high affinity toward TCs, are recognized as excellent absorbents for removal of TCs from food and water samples. Herein, the utilization of MOFs in the adsorption of TC from food and water samples is deliberated including the underlying mechanisms and various factors that affect the adsorption and degradation of TCs. The strategy may be extendible to other pollutants as well.

Open-Metal and Carboxamide-Tethered Redox-Active Undulated Framework for Mild-Condition Synthesis of Therapeutic Drugs and Tandem Catalysis with Size-Selectivity

A mixed-ligand-based thermo-chemically robust and undulated metal-organic framework (MOF) is developed that embraces carboxamide moiety-grafted porous channels and activation-induced generation of open-metal site (OMS). The guest-free MOF acts as an outstanding heterogeneous catalyst in Hantzsch condensation for electronically assorted substrates with low catalyst loading and short duration under greener conditions than the reported materials. Besides Lewis acidic OMS, the carboxamide group activates the substrate via two-point hydrogen bonding, highlighting the effectiveness of custom-made functionalities in this multi-component reaction. Importantly, the framework demonstrates first ever one-pot synthesis of 1,4-dihydropyridine-based antihypertensive drug foridon, along with four therapeutic molecules ethidine, nifedipine, nemadipine B and Nitrendipine, which are characterized via X-ray crystallography besides conventional spectroscopic analyses. The integration of redox-active Co(II) center and acid-base dual sites benefit the activated MOF catalyzing mild-condition alcohol oxidation-Knoevenagel condensation to produce benzylidene malononitriles with wide substrate tolerance and multicyclic performance. For both the multi-component and atom-economic reactions, astutely designed control experiments and density functional theory-based reaction energy profile rationalize synergistic catalysis via pore-decked antagonistic sites that predominantly transpires inside the MOF channel. This study marks a paradigm shift in sustainable catalysis through task-specific functionality fuelling, and provides valuable insights on structure-property synergism at the cutting-edge MOF design.

Crystal-size-dependent Optical Properties of H-atoms on the Nodes of Ti-based Metal-organic Framework

Proton-coupled electron transfer (PCET) reactions are fundamental to energy storage and conversion processes. By coupling electrons with protons, the net charge neutrality is retained, preventing electrode decomposition due to charge imbalance. PCET reactions with equimolar amounts of protons and electrons can be considered as a net H-atom transfer (HAT) reaction. Many redox-active metal-organic frameworks (MOFs) have demonstrated that the inorganic nodes and/or the organic linkers can be tailored to undergo HAT reactions. In particular, the Ti-oxo nodes of the MOF focused on this work, Ti-MIL-125, can accept up to two H-atoms. H-atom binding on the nodes of Ti-MIL-125 has long been known to correlate with the color change in the crystals from white to blue-black, but its exact optical properties, such as molar extinction coefficient (ϵ) and wavelength with maximum ϵ, λmax, have yet to be determined. The presented work determines these parameters using colloidally stable Ti-MIL-125 of three different crystallite sizes. These studies revealed that both parameters are highly dependent on the crystal size and are likely indicating a distortion of the Ti-oxo nodes at the crystal surface. Together, these highlight the importance of considering defects in understanding HAT reactions of otherwise structurally uniform and periodic MOFs.

Mesoporous Atomically Dispersed Fe Catalysts with Enhanced Nonradical Pathways in Fenton-like Reactions: The Role of SiO2 Templates

Single-atom catalysts (SACs) are extensively applied in Fenton-like catalytic processes to treat water pollutants. However, the role of the porous structures of SACs supports in catalytic reactions is often overlooked despite its significant contribution to mass diffusion during the reaction. Herein, we adopted a hard-template-assisted approach to fabricate Fe-based SACs (Fe-SACs) featuring a mesoporous architecture. The SiO2 template not only adjusts the pore architecture of the support but also facilitates the conversion of active sites from nanoscale sites to single-atom sites, thereby improving the selectivity for pollutant degradation via nonradical pathways (singlet oxygen and electron transfer mechanism). The experimental results demonstrated that using large-sized SiO2 (∼200 nm) as a template leads to metal aggregation on its surface, forming Fe nanoparticles (Fe-NPs). Fe-NPs exhibit narrow pore structures that prevent peroxymonosulfate (PMS) from being activated, resulting in a slow degradation of pollutants primarily through radical pathways. In contrast, employing small-sized SiO2 (∼10 nm) as a hard template not only produces supports with mesoporous structures but also promotes the building of single-atom active sites. The prepared Fe-SACs effectively activated PMS through nonradical pathways and removed contaminants at a rate k of 0.89 min-1, 33 times faster than Fe-NPs. This template-assisted method sheds light on the synthesis of effective Fenton-like catalysts with porous structures that enhance the efficient breakdown of contaminants in wastewater.

Hybrid Metal-Organic Frameworks (MOFs) for Various Catalysis Applications

Porous materials have been gaining popularity in catalysis applications, solving the current ecological challenges. Metal-organic frameworks (MOFs) are especially noteworthy for their high surface areas and customizable chemistry, giving them a wide range of potential applications in catalysis remediation. The review study delves into the various applications of MOFs in catalysis and provides a comprehensive summary. This review thoroughly explores MOF materials, specifically focusing on their diverse catalytic applications, including Lewis catalysis, oxidation, reduction, photocatalysis, and electrocatalysis. Also, this study emphasizes the significance of high-performance MOF materials, which possess adjustable properties and exceptional features, as a novel approach to tackling technological challenges across multiple sectors. MOFs make it an ideal candidate for catalytic reactions, as it enables efficient conversion rates and selectivity. Furthermore, the tunable properties of MOF make it possible to tailor its structure to suit specific catalytic requirements. This feature improves performance and reduces costs associated with traditional catalysts. In conclusion, MOF materials have revolutionized the field of catalysis and offer immense potential in solving various technological challenges across different industries.

Electrochemically Determined and Structurally Justified Thermochemistry of H atom Transfer on Ti-Oxo Nodes of the Colloidal Metal-Organic Framework Ti-MIL-125

Titanium dioxide (TiO2) has long been employed as a (photo)electrode for reactions relevant to energy storage and renewable energy synthesis. Proton-coupled electron transfer (PCET) reactions with equimolar amounts of protons and electrons at the TiO2 surface or within the bulk structure lie at the center of these reactions. Because a proton and an electron are thermochemically equivalent to an H atom, these reactions are essentially H atom transfer reactions. Thermodynamics of H atom transfer has a complex dependence on the synthetic protocol and chemical history of the electrode, the reaction medium, and many others; together, these complications preclude the understanding of the H atom transfer thermochemistry with atomic-level structural knowledge. Herein, we report our success in employing open-circuit potential (EOCP) measurements to quantitatively determine the H atom transfer thermochemistry at structurally well-defined Ti-oxo clusters within a colloidally stabilized metal-organic framework (MOF), Ti-MIL-125. The free energy to transfer H atom, Ti3+O-H bond dissociation free energy (BDFE), was measured to be 68(2) kcal mol-1. To the best of our understanding, this is the first report on using EOCP measurements to quantify thermochemistry on any MOFs. The proton topology, the structural change upon the redox reaction, and BDFE values were further quantitatively corroborated using computational simulations. Furthermore, comparisons of the EOCP-derived BDFEs of Ti-MIL-125 to similar parameters in the literature suggest that EOCP should be the preferred method for quantitatively accurate BDFE calculations. The reported success in employing EOCP for nanosized Ti-MIL-125 should lay the ground for thermochemical measurements of other colloidal systems, which are otherwise challenging. Implications of these measurements on Ti-MIL-125 as an H atom acceptor in chemical reactions and comparisons with other MOFs/metal oxides are discussed.

Unlocking the catalytic potential of heterogeneous nonprecious metals for selective hydrogenation reactions

Selective hydrogenation has been employed extensively to produce value-added chemicals and fuels, greatly alleviating the problems of fossil resources and green synthesis. However, the design and synthesis of highly efficient catalysts, especially those that are inexpensive and abundant in the earth's crust, is still required for basic research and subsequent industrial applications. In recent years, many studies have revealed that the rational design and synthesis of heterogeneous catalysts can efficaciously improve the catalytic performance of hydrogenation reactions. However, the relationship between nonprecious metal catalysts and hydrogenation performance from the perspective of different catalytic systems still remains to be understood. In this review, we provide a comprehensive and systematic overview of the recent advances in the synthesis of nonprecious metal catalysts for heterogeneous selective hydrogenation reactions including thermocatalytic hydrogenation/transfer hydrogenation, photocatalytic hydrogenation and electrocatalytic reduction. In addition, we also aim to provide a clear picture of the recent design strategies and proposals for the nonprecious metal catalysed hydrogenation reactions. Finally, we discuss the current challenges and future research opportunities for the precise design and synthesis of nonprecious metal catalysts for selective hydrogenation reactions.

Anchoring Pt Single-Atom Sites on Vacancies of MgO(Al) Nanosheets as Bifunctional Catalysts to Accelerate Hydrogenation-Cyclization Cascade Reactions

The direct hydrogenation of 2-nitroacylbenzene to 2,1-benzisoxazole presents a significant challenge in the pharmaceutical and fine chemicals industries. In this study, a defect engineering strategy is employed to create bifunctional single-atom catalysts (SACs) by anchoring Pt single atoms onto metal vacancies within MgO(Al) nanosheets. The resultant Pt1/MgO(Al) SAC displays an exceptional catalytic activity and selectivity in the hydrogenation-cyclization of 2-nitroacylbenzene, achieving a 97.5 % yield at complete conversion and a record-breaking turnover frequency of 458.8 h-1 under the mild conditions. The synergistic catalysis between the fully exposed single-atom Pt sites within a unique Pt-O-Mg/Al moiety and the abundant basic sites of the MgO(Al) support is responsible for this outstanding catalytic performance. The current work, therefore, paves the way for developing bifunctional or multifunctional SACs that can enhance efficient organocatalytic conversions.

Antimicrobial zeolites and metal-organic frameworks

The current surge in antibiotic resistance and the emergence of pandemics have created an urgent need for novel antimicrobial strategies. The controlled release of antimicrobial active principles remains the most viable strategy to date, and transition metal ions currently represent the main alternative to antibiotics. In this review, we explore the potential of two types of materials, zeolites and metal-organic frameworks (MOFs), for the controlled release of antimicrobial active principles, notably transition metal ions. These materials have unique crystalline microporous structures that act as reservoirs, enabling sustained bactericidal effects in various applications such as coatings, packaging, and medical devices. However, there are currently no convenient and standardised methods for evaluating their metal ion release and antimicrobial efficacy. This work discusses analytical techniques and the proposed mechanisms of action while highlighting recent advances in film, membrane, and coating technologies. By addressing the current limitations, microporous materials can revolutionise antimicrobial approaches, offering enhanced effectiveness and long-term sustainability.

Reticular Imine-Linked Coordination Polymers Based on Paddlewheel Diruthenium/Dirhodium Nodes: Synthesis and Metal-Site Dependent Photocatalytic Reduction of CO2

The paddlewheel-type dimetal core ([M2]) is a ubiquitous motif in the nodes in coordination polymers (CPs) and metal-organic frameworks (MOFs). However, their preparation has relied on ligand-substitution-labile metal ions owing to challenges associated with crystallization. Consequently, examples featuring ligand-substitution-inert metal ions, such as Ru or Rh, are scarce. This study presents the synthesis of novel reticular imine-linked CPs incorporating the paddlewheel-type diruthenium(II, II) ([Ru2 II,II]; 1-Ru) or dirhodium(II, II) ([Rh2 II,II]; 1-Rh) subunits. The synthetic approach involved a Schiff base dehydration condensation reaction between p-formylbenzoate-bridged [Ru2 II,II] or [Rh2 II,II] precursors (i. e., CHO-Ru and CHO-Rh, respectively) and 2,5-dimethyl-1,4-phenylenediamine in a 1 : 2 ratio. The catalytic activities of 1-Ru and 1-Rh for the photochemical reduction of CO2 in a heterogeneous system depended on the metal site. The 1-Ru system exhibited exceptional selectivity, generating 3.0×104 μmol g-1 of CO after 24 h of irradiation, whereas the 1-Rh system generated a lower amount of CO (3.2×103 μmol g-1). The catalytic activity of 1-Ru ranked with that of all relevant catalytic systems. This study paves the way for the exploration of [Ru2 II,II]- or [Rh2 II,II]-based polymers with open metal site-dependent functional properties.

Electronic regulation of single-atomic Ti sites on metal hydroxide for boosting photocatalytic CO2 reduction

Photocatalytic CO2 reduction is considered a sustainable method to address energy and environmental issues by converting CO2 into fuels and chemicals, yet the performance is still unsatisfactory. Single atom catalysts hold promising potential in photocatalysis, but the selection of metal species is still limited, especially in early transition metals. Herein, inspired by the structure of anatase TiO2, single Ti sites were successfully incorporated into a metal hydroxide support for the first time via cationic defects, significantly enhancing the photocatalytic performance by more than 30 times (from 0.26 to 8.09 mmol g-1 h-1). Based on the theoretical calculation and in situ characterization, the enhancement of photocatalytic performance can be attributed to the regulation of the electronic structure by the introduction of atomically dispersed Ti sites, leading to stronger binding with intermediates and enhanced charge transfer.

Spatiotemporally Guided Single-Atom Bionanozyme for Targeted Antibiofilm Treatment

The heterogeneous and dynamic microenvironment of biofilms complicates bacterial infection treatment. Nanozyme catalytic therapy has recently been promising in treating biofilm infections. However, active nanozymes designed with the required precision targeting the biofilm microenvironment are lacking. This work proposes a spatiotemporally guided single-atom bionanozyme (BioSAzyme) for targeted antibiofilm therapy based on protein engineering of copper single-atom nanozyme (Cu SAzyme). The Cu SAzyme, synthesized via a novel mechanochemistry-assisted method, features highly accessible Cu-N4 active sites exposed on 2D N-doped carbon, exhibiting excellent triple enzyme-like activities according to experimental results and density functional theory calculations. Inheriting biofunctionality from both glucose oxidase and concanavalin A, BioSAzyme can localize the biofilm glycocalyx and catalyze endogenous glucose into H₂O₂ and gluconic acid, thus triggering multiplex cascade reactions with pH self-adaption to consume glucose and glutathione and generate •OH radicals. This spatiotemporally guided bionanocatalytic agent effectively inhibits E. coli O157: H7 and methicillin-resistant S. aureus biofilms in vitro and in vivo. Taking together, this work opens up new avenues for the rational design of single-atom nanozymes for precise antibiofilm therapy.

Robust Cd(4,5-Imdb)-MOF for Lewis-Acid Assisted Catalysis and Selective Sensing of 2,4,6-Trinitrophenol

Developing multifunctional metal-organic frameworks (MOFs) for effective catalysis and sensing remain a significant challenge. This study presents the synthesis of an imidazole-based angular linker, 4,4'-(1-methyl-1H-imidazole-4,5-diyl)dibenzoic acid (4,5-H2Imdb), which is used in the synthesis of the Cd(4,5-Imdb)-MOF. This MOF demonstrates robust and recyclable properties, making it suitable for solvent-free Strecker synthesis and in the detection of the secondary explosive 2,4,6-trinitrophenol (TNP) molecule, with a limit of detection (LOD) of 7.5 ppb in methanol. The material's hydrolytic stability and reusability are thoroughly evaluated. Additionally, density functional theory (DFT) calculations provide insights into the selective detection mechanism of TNP. These findings highlight the potential of Cd(4,5-Imdb)-MOF in catalysis and sensing applications.

Fabrication of Ultrahigh-Loading Dual Copper Sites in Nitrogen-Doped Porous Carbons Boosting Electroreduction of CO2 to C2H4 Under Neutral Conditions

Synthesis of high-loading atomic-level dispersed catalysts for highly efficient electrochemical CO2 reduction reaction (eCO2RR) to ethylene (C2H4) in neutral electrolyte remain challenging tasks. To address common aggregation issues, a host-guest strategy is employed, by using a metal-azolate framework (MAF-4) with nanocages as the host and a dinuclear Cu(I) complex as the guest, to form precursors for pyrolysis into a series of nitrogen-doped porous carbons (NPCs) with varying loadings of dual copper sites, namely NPCMAF-4-Cu2-21 (21.2 wt%), NPCMAF-4-Cu2-11 (10.6 wt%), and NPCMAF-4-Cu2-7 (6.9 wt%). Interestingly, as the loading of dual copper sites increased from 6.9 to 21.2 wt%, the partial current density for eCO2RR to yield C2H4 also gradually increased from 38.7 to 93.6 mA cm-2. In a 0.1 m KHCO3 electrolyte, at -1.4 V versus reversible hydrogen electrode (vs. RHE), NPCMAF-4-Cu2-21 exhibits the excellent performance with a Faradaic efficiency of 52% and a current density of 180 mA cm-2. Such performance can be attributed to the presence of ultrahigh-loading dual copper sites, which promotes C─C coupling and the formation of C2 products. The findings demonstrate the confinement effect of MAF-4 with nanocages is conducive to the preparation of high-loading atomic-level catalysts.

Single Atom Catalysts Based on Earth-Abundant Metals for Energy-Related Applications

Anthropogenic activities related to population growth, economic development, technological advances, and changes in lifestyle and climate patterns result in a continuous increase in energy consumption. At the same time, the rare metal elements frequently deployed as catalysts in energy related processes are not only costly in view of their low natural abundance, but their availability is often further limited due to geopolitical reasons. Thus, electrochemical energy storage and conversion with earth-abundant metals, mainly in the form of single-atom catalysts (SACs), are highly relevant and timely technologies. In this review the application of earth-abundant SACs in electrochemical energy storage and electrocatalytic conversion of chemicals to fuels or products with high energy content is discussed. The oxygen reduction reaction is also appraised, which is primarily harnessed in fuel cell technologies and metal-air batteries. The coordination, active sites, and mechanistic aspects of transition metal SACs are analyzed for two-electron and four-electron reaction pathways. Further, the electrochemical water splitting with SACs toward green hydrogen fuel is discussed in terms of not only hydrogen evolution reaction but also oxygen evolution reaction. Similarly, the production of ammonia as a clean fuel via electrocatalytic nitrogen reduction reaction is portrayed, highlighting the potential of earth-abundant single metal species.

Aldehyde Directed In Situ Loading of Ag Nanodots Around the Open Metal Sites of MOFs for the Tandem Catalysis of Nitrate to Ammonia

Both spatial arrangement and intrinsic activity of electrocatalysts with dual-active sites are widely designed to match the coupling reaction between nitrate and water, in which most of the reactive intermediates can be optimized to achieve a high yield rate of ammonia. Herein, by introducing the aldehyde group inside metal-organic frameworks (MOFs) in advance, an aldehyde-induced method is achieved to direct the in situ nucleation of Ag nanodots depending on the mesopores of MOFs via a simple silver mirror reaction. The key point here is that the spatial arrangement between the aldehyde group and open metal sites is fixed end to end, which makes the aldehyde group a built-in redox-active site to drive the in situ nucleation of Ag nanodots next to the open metal sites of MOFs. Accordingly, by varying the metal sites of MOFs, a group of M-MOFs@Ag (M = Fe, Co, Ni, Cu, etc.) hybrids with dual active sites are acquired. Taking Ni-MOFs@Ag as an example, the interaction between Ni2+ and Ag sites makes it available for the tandem catalysis of nitrate-to-ammonia, in which the H· and NO2 - generated on the open Ni2+ sites and Ag nanodots, respectively, can migrate to each other to evolve into ammonia.

Location-Specific Microenvironment Modulation Around Single-Atom Metal Sites in Metal-Organic Frameworks for Boosting Catalysis

Despite coordination environment of catalytic metal sites has been recognized to be of great importance in single-atom catalysts (SACs), a significant challenge remains in the understanding how the location-specific microenvironment in the higher coordination sphere influences their catalysis. Herein, a series of Cu-based SACs, namely Cu1/UiO-66-X (X=-NO2, -H, and -NH2), are successfully constructed by anchoring single Cu atoms onto the Zr-oxo clusters of metal-organic frameworks (MOFs), i.e., UiO-66-X. The -X functional groups dangling on the MOF linkers could be regarded as location-specific remote microenvironment to regulate electronic properties of the single Cu atoms. Remarkably, they exhibit significant differences in the catalysis toward the hydroboration of alkynes. The activity follows the order of Cu1/UiO-66-NO2 > Cu1/UiO-66 > Cu1/UiO-66-NH2 under identical reaction conditions, where Cu1/UiO-66-NO2 showcases the phenylacetylene conversion of 92 %, ~3.5 times higher efficiency than that of Cu1/UiO-66-NH2. Experimental and calculation results jointly support that the Cu electronic structure is modulated by the location-specific microenvironment, thereby regulating the product desorption and promoting the catalysis.

Incorporation of enzyme-mimic species in porous materials for the construction of porous biomimetic catalysts

The unique catalytic properties of natural enzymes have inspired chemists to develop biomimetic catalyst platforms for the intention of retaining the unique functions and solving the application limitations of enzymes, such as high costs, instability and unrecyclable ability. Porous materials possess unique advantages for the construction of biomimetic catalysts, such as high surface areas, thermal stability, permanent porosity and tunability. These characteristics make them ideal porous matrices for the construction of biomimetic catalysts by immobilizing enzyme-mimic active sites inside porous materials. The developed porous biomimetic catalysts demonstrate high activity, selectivity and stability. In this feature article, we categorize and discuss the recently developed strategies for introducing enzyme-mimic active species inside porous materials, which are based on the type of employed porous materials, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), molecular sieves, porous metal silicate (PMS) materials and porous carbon materials. The advantages and limitations of these porous materials-based biomimetic catalysts are discussed, and the challenges and future directions in this field are also highlighted.

Hierarchically Ordered Pore Engineering of Carbon Supports with High-Density Edge-Type Single-Atom Sites to Boost Electrochemical CO2 Reduction

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in-plane sites. However, creating single-atom catalysts with high-density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal-organic framework-based materials to construct high-density edge-type single-atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single-atomic Ni sites on the ordered macroporous carbon with ultra-thin hollow walls (Ni/H-OMC) exhibit Faraday efficiencies of CO above 90% in an ultra-wide potential window of 600 mV and a turnover frequency of 3.4 × 104 h-1, much superior than that of the microporous material with dominant plane-type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron-rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn-CO2 battery using the Ni/H-OMC cathode shows an unprecedentedly high power density of 15.9 mW cm-2 and maintains an exceptionally stable charge-discharge performance over 100 h.

Pioneering technologies over time to rehabilitate crude oil-contaminated ecosystems: a review

The unremitting pollution of our environment induced by crude oil spillage and drilling site accidents has jeopardized every living species in the biological ecosystem. Removing heavy crude oil constituents with the help of traditional and mainstream oil sorbents because of their ingrained raised viscosities is a strenuous venture. Lighter distillates of crude oil, like condensate, do not aggregate with tremulous shine on the aquatic surface nor settle at the bottom sediment of the water bodies like the heavier components do with time. Fabricating optimally designed materials capable of capturing, degrading, or removing toxic chemical constituents of this fossil fuel is critical in this modern era. This review comprehensively discusses the evolution of scientific technologies developed to separate these constituents from land and aquatic bodies. We provide an overview of the latest physical and chemical strategies and prevalent biological remediation schemes for removing these pollutants from soils and water for environmental protection. The article highlights the urgency of preventing oil spill accidents, whose anticipation is challenging to harness. A spectrum of advanced functional methodologies is also discussed to adequately treat discharged hydrocarbon contaminants, establish public safety, and pave the path to enhancing the circular economy metrics linked with oil industries.

Recent Functionalized Strategies of Metal-Organic Frameworks for Anode Protection of Aqueous Zinc-Ion Battery

The inherent benefits of aqueous Zn-ion batteries (ZIBs), such as environmental friendliness, affordability, and high theoretical capacity, render them promising candidates for energy storage systems. Nevertheless, the Zn anodes of ZIBs encounter severe challenges, including dendrite formation, hydrogen evolution reaction, corrosion, and surface passivation. These would result in the infeasibility of ZIBs in practical situations. To this end, artificial interfaces with functionalized materials are crafted to protect the Zn anode. They have the capability to modulate the zinc ion flux in proximity to the electrode surface and shield it from aqueous electrolytes by leveraging either size effects or charge effects. Considering metal-organic frameworks (MOFs) with tunable pore size, chemical composition, and stable framework structures, they have emerged as effective materials for building artificial interfaces, prolonging the lifespan, and improving the unitization of Zn anode. In this review, the contributions of MOFs for protecting Zn anode, which mainly involves facilitating homogeneous nucleation, manipulating selective deposition, regulating ion and charge flux, accelerating Zn desolvation, and shielding against free water and anions are comprehensively summarized. Importantly, the future research trajectories of MOFs for the protection of the Zn anode are underscored, which may propose new perspectives on the practical Zn anode and endow the MOFs with high-value applications.

A general flame aerosol route to kinetically stabilized metal-organic frameworks

Metal-organic frameworks (MOFs) are highly attractive porous materials with applications spanning the fields of chemistry, physics, biology, and engineering. Their exceptional porosity and structural flexibility have led to widespread use in catalysis, separation, biomedicine, and electrochemistry. Currently, most MOFs are synthesized under equilibrium liquid-phase reaction conditions. Here we show a general and versatile non-equilibrium flame aerosol synthesis of MOFs, in which rapid kinetics of MOF formation yields two distinct classes of MOFs, nano-crystalline MOFs and amorphous MOFs. A key advantage of this far-from-equilibrium synthesis is integration of different metal cations within a single MOF phase, even when this is thermodynamically unfavorable. This can, for example, produce single-atom catalysts and bimetallic MOFs of arbitrary metal pairs. Moreover, we demonstrate that dopant metals (e.g., Pt, Pd) can be exsolved from the MOF framework by reduction, forming nanoclusters anchored on the MOF. A prototypical example of such a material exhibited outstanding performance as a CO oxidation catalyst. This general synthesis route opens new opportunities in MOF design and applications across diverse fields and is inherently scalable for continuous production at industrial scales.

Selective Monoborylation of Methane by a Mono Bipyridyl-Nickel(II) Hydride Catalyst

We report the development of an earth-abundant metal catalyst for methane C-H borylation. The post-synthetic metalation of bipyridine-functionalized zirconium metal-organic framework (MOF) with NiBr2, followed by treatment with NaEt3BH affords MOF-supported monomeric bipyridyl-nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 °C using pinacolborane (HBpin) to afford CH3Bpin in 61 % yield with a turnover number (TON) up to 1388. The confinement of the active NiH2-species within the uniformly porous MOF allows selective monoborylation of methane via shape-selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF-Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl-nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover-limiting σ-bond metathesis. This work shows promise in designing MOF-based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

Structural engineering in hierarchical nanoarchitectures of metal-organic frameworks and their derivatives

Metal-organic frameworks (MOFs) have attracted much attention owing to their tuneable structures, high surface areas, and good functionalization. Nanoreactors derived from various MOFs are now widely used in heterogeneous catalysis, electrocatalysis and photocatalysis. The nanoarchitectures of MOFs and their derivatives have a great impact on mass and energy transfer pathways, thus affecting the activity and selectivity of the catalysts. In this review, we intend to provide a universal survey of reported methods to synthesize MOF-based core-satellite, core-shell, yolk-shell and hollow-shell structures or their derivatives in recent years and present a continuous evolution among them. We hope that this review could provide some perspectives for exploring new facile methods to prepare different hierarchical nanoarchitectures of MOFs or their derivatives.

Strategy of Constructing Ratio-Dependent Coordination Polymer probes and Their Film Application with a Smart Phone for Detection of Lomefloxacin Hydrochloride and Sodium Salicylate

Lomefloxacin hydrochloride (LMFX) and sodium salicylate (SS) are important targets for real-time detection due to their widespread uses in daily life; accurate and portable monitoring of LMFX and SS is crucial for human health concerns accordingly. Developing a precise and smart platform for determination of the above analytes remains a significant challenge. Herein, a high-sensitivity platform incorporating a luminescence electrospinning film, self-designed smart-phone app, and portable 3D printing device has been developed to identify LMFX and SS. In this work, two heterometallic coordination polymers with two-dimensional layer structures have been synthesized based on 2,2'-oxidiacetic acid ligand (H2oda), namely, [LnPb(oda)2(CH3COO)]n [Ln = Eu (IMU-1); Tb (IMU-2)]. IMU-1 and IMU-2 were ratio-dependent luminescence probes, which could selectively and sensitively sense with LMFX and SS, respectively. Additionally, the synthesized electrospinning films incorporating IMU-1 and IMU-2 were employed to identify LMFX and SS. Both films could rapidly photograph and color-capture through a portable 3D printing device, along with a self-designed smart-phone app that enabled convenient and quick determination of the concentrations of the above analytes. Remarkably, the mechanism exploration indicated that electron transfer from ligands to analytes affected the antenna effect and further utilized the intrinsic luminescence of analytes along with the luminescence quenching of Ln3+ ions. Furthermore, a strategy for constructing ratio-based fluorescent probes by exploiting the luminescence of analytes and Ln3+ ions in host coordination polymers is proposed. This work provides a new insight by combining luminescence probes, portable devices, and a smart-phone app for real-time detection of drugs and food additives.

Second-shell modulation on porphyrin-like Pt single atom catalysts for boosting oxygen reduction reaction

The first coordination shell is considered crucial in determining the performance of single atom catalysts (SACs), but the significance of the second coordination shell has been overlooked. In this study, we developed a post-doping strategy to realize predictable and controlled modulation on the second coordination shell. By incorporating a P atom into the second coordination shell of a porphyrin-like Pt SAC, the charge density at the Fermi level of Pt single atom increases, enhancing its intrinsic activity. Moreover, the P atom shows stronger adsorption towards large size anions (ClO4 -) than Pt atoms, preventing the Pt site poisoning in acid. As a result, the Pt-N4P-C catalyst exhibits significantly higher activity than the Pt-N4-C catalyst. It even outperforms commercial Pt/C (20 wt% Pt) with a Pt content of only 0.22 wt% in both alkaline and acidic solutions. This work indicates the second coordination shell modulation also greatly impacts the performance of SACs.

Dual Metallosalen-Based Covalent Organic Frameworks for Artificial Photosynthetic Diluted CO2 Reduction

Directly converting CO2 in flue gas using artificial photosynthetic technology represents a promising green approach for CO2 resource utilization. However, it remains a great challenge to achieve efficient reduction of CO2 from flue gas due to the decreased activity of photocatalysts in diluted CO2 atmosphere. Herein, we designed and synthesized a series of dual metallosalen-based covalent organic frameworks (MM-Salen-COFs, M: Zn, Ni, Cu) for artificial photosynthetic diluted CO2 reduction and confirmed their advantage in comparison to that of single metal M-Salen-COFs. As a results, the ZnZn-Salen-COF with dual Zn sites exhibits a prominent visible-light-driven CO2-to-CO conversion rate of 150.9 μmol g-1 h-1 under pure CO2 atmosphere, which is ~6 times higher than that of single metal Zn-Salen-COF. Notably, the dual metal ZnZn-Salen-COF still displays efficient CO2 conversion activity of 102.1 μmol g-1 h-1 under diluted CO2 atmosphere from simulated flue gas conditions (15 % CO2), which is a record high activity among COFs- and MOFs-based photocatalysts under the same reaction conditions. Further investigations and theoretical calculations suggest that the synergistic effect between the neighboring dual metal sites in the ZnZn-Salen-COF facilitates low concentration CO2 adsorption and activation, thereby lowering the energy barrier of the rate-determining step.

Effects of zeolite imidazole frameworks on rice seedlings (Oryza sativa L.): Phytotoxicity, transformation, and bioaccumulation

Zeolite imidazole frameworks (ZIFs), a class of the metal organic framework, have been extensively studied in environmental applications. However, their environmental fate and potential ecological impact on plants remain unknown. Here, we investigated the phytotoxicity, transformation, and bioaccumulation processes of two typical ZIFs (ZIF-8 and ZIF-67) in rice (Oryza sativa L.) under hydroponic conditions. ZIF-8 and ZIF-67 in the concentration of 50 mg/L decreased root and shoot dry weight maximally by 55.2% and 27.5%, 53.5% and 37.5%, respectively. The scanning electron microscopy (SEM) imaging combined with X-ray diffraction (XRD) patterns revealed that ZIFs on the root surface gradually collapsed and transformed into nanosheets with increasing cultivation time. The fluorescein isothiocyanate (FITC) labeled ZIFs were applied to trace the uptake and translocation of ZIFs in rice. The results demonstrated that the transformed ZIFs were mainly distributed in the intercellular spaces of rice root, while they cannot be transported to culms and leaves. Even so, the Co and Zn contents of rice roots and shoots in the ZIFs treated groups were increased by 1145% and 1259%, 145% and 259%, respectively, compared with the control groups. These findings suggested that the phytotoxicity of ZIFs are primarily attributed to the transformed ZIFs and to a less extent, the metal ions and their ligands, and they were internalized by rice root and increased the Co and Zn contents of shoots. This study reported the transformation of ZIFs and their biological effectiveness in rice, highlighting the potential environmental hazards and risks of ZIFs to crop plants.

Bifunctional In-MOFs for Selective and Sensitive Detection of Trace Nitrobenzene Compounds in Water and Possessing High Proton Conductivity

With the escalating prevalence of terrorism and global environmental pollution, nitroaromatic compounds (NACs) have increasingly come into focus as the primary culprit. To counter these challenges, it is imperative to develop simple and efficient methods for detecting NACs. Considering the electron-deficient structure of NAC molecules, this paper constructed a novel three-dimensional In-MOF with permanent porosity using electron-rich organic molecules 4'-[1,2,2-tris(3',5'-dicarboxy[1,1'-biphenyl]-4-yl)ethenyl]-[1,1'-biphenyl]-3,5-dicarboxylic acid (H8ETTB) for fluorescence detection by photoinduced electron transfer. The results indicated that In-ETTB can sensitively detect trace NACs in water. In-ETTB exhibited the best detection performance for 3-NP, achieving a Ksv value of 8.75 × 104 M-1 with a limit of detection of 0.27 μΜ in aqueous solution; this belongs to a relatively high level among the reported metal organic framework (MOF) materials. Subsequently, anti-interference experiments revealed that In-ETTB exhibits strong specificity fluorescence recognition of NACs, and it could still maintain its structural integrity and fluorescence emission intensity even after 7 cycles of testing. We confirmed that the fluorescence detection of NACs was due to a combined effect of competitive absorption and photoinduced electron transfer through experimental collaboration DFT calculations in detail. Meanwhile, the proton conductivity reached 2.45 × 10-2 S·cm-1 at 98% relative humidity and 90 °C, which is also a high level in MOFs. This work provides a universal method theoretical basis for designing NAC detectors with practical application prospects.

f-π* Back-Bonding Orbital Induced by a Lutetium-Based Conducting Metal-Organic Framework Promotes Highly Selective CO2-to-CH4 Conversion at Low Potential

The research on electrocatalytic carbon dioxide reduction (ECR) catalysts using renewable energy is particularly crucial in energy conversion studies, especially for viable hydrocarbon production. This study employs density functional theory calculations to screen a series of non-radioactive lanthanide two-dimensional metal-organic frameworks (MOFs) for product selectivity in ECR. Based on theoretical screening, our focus is on a lutetium (Lu)-based conducting MOF (Lu-HHTP), which exhibits a Faradaic efficiency of approximately 77 % for methane (CH4) production and maintains a stable current density of -280 mA/cm2 at -1.1 V vs. RHE. In situ electrochemical experiments and material characterization demonstrate that the Lu sites possess high coordination stability and structural recoverability during catalytic CO2 reduction, attributed to the overlap between Lu's f-orbitals and the π*-orbitals of the ligand O, and the formation of back bonding orbitals between the f-orbitals of Lu and the π* orbitals of CO contribute increasing CH4 selectivity and lowering the potential. This study leverages rare-earth MOF-type materials, offering a novel approach to addressing low conductivity and stabilizing rare-earth materials, thereby establishing a theoretical framework for the conversion of linearly adsorbed *CO into hydrocarbons.

Effect of pore structure in bismuth metal-organic framework nanorod derivatives on adsorption and organic pollutant degradation

This study explores the synthesis, characterization, and photocatalytic properties of bismuth metal-organic framework (Bi-MOF) nanorods and their derivatives such as Ag/Bi-MOF and Ag/Bi2O3. Bi-MOF nanorods exhibit significant photocatalytic activity under visible light, with the addition of silver (Ag) enhancing electron-hole pair separation and reducing their recombination. This leads to improved photocatalytic performance, particularly in the degradation of organic pollutants such as Rhodamine B (RhB) and Methylene Blue (MB). The results show that Bi-MOF and its derivatives demonstrate excellent chemical stability and high performance in photocatalytic applications, even when subjected to high temperatures and tested across a wide pH range. The large surface area and microporous structure facilitate selective adsorption of small organic molecules like MB. The pores and large surface area not only provide numerous active sites but also enhance the interaction between reactants and the catalyst surface, improving photocatalytic efficiency. Bi-MOF and its derivatives perform optimally across a broad pH range, from acidic to alkaline environments, where strong oxidizing hydroxyl radicals (·OH) are easily formed, aiding in the effective degradation of organic compounds. The study also shows that Bi-MOF and its derivatives can be reused multiple times without significant loss in performance. This research contributes to the development of advanced materials for environmental remediation, highlighting the potential of Bi-MOF-based nanocomposites in practical applications.

Unveiling the scope and perspectives of MOF-derived materials for cutting-edge applications

Although synthesis and design of MOFs are crucial factors to the successful implementation of targeted applications, there is still lack of knowledge among researchers about the synthesis of MOFs and their derived composites for practical applications. For example, many researchers manipulate study results, and it has become quite difficult to quit this habit specifically among the young researchers Undoubtedly, MOFs have become an excellent class of compounds but there are many challenges associated with their improvement to attain diverse applications. It has been noted that MOF-derived materials have gained considerable interest owing to their unique chemical properties. These compounds have exhibited excellent potential in various sectors such as energy, catalysis, sensing and environmental applications. It is worth mentioning that most of the researchers rely on commercially available MOFs for use as precursor supports, but it is an unethical and wrong practice because it prevents the exploration of the hidden diversity of similar materials. The reported studies have significant gaps and flaws, they do not have enough details about the exact parameters used for the synthesis of MOFs and their derived materials. For example, many young researchers claim that MOF-based materials cannot be synthesized as per the reported instructions for large-scale implementation. In this regard, current article provides a comprehensive review of the most recent advancements in the design of MOF-derived materials. The methodologies and applications have been evaluated together with their advantages and drawbacks. Additionally, this review suggests important precautions and solutions to overcome the drawbacks associated with their preparation. Applications of MOF-derived materials in the fields of energy, catalysis, sensing and environment have been discussed. No doubt, these materials have become excellent class but there are still many challenges ahead to specify it for the targeted applications.

Palladium(II) Modulation Enhances the Water Stability and Aqueous 99TcO4-/ReO4- Removal Performance of Metal-Organic Frameworks

Improving the water stability of metal-organic frameworks (MOFs) is essential for their use in water pollution treatment and environmental remediation, though it remains technically challenging. Herein, we report a novel cationic MOF constructed with [Th6O4(OH)4(COO)12] units and [CoN4·Cl2] units possessing a ftw-type topology (denoted as 1-Th-Co). 1-Th-Co itself exhibited poor water stability but excellent stability following a palladium(II) modulation strategy. Experimental studies reveal that Co(II) ions in 1-Th-Co were replaced by Pd(II) ions through cation exchange in N,N-diethylformamide (yielding 1-Th-Pd). The planar PdN4 units in 1-Th-Pd were responsible for improving the water stability of the framework. As a result, 1-Th-Pd offered excellent stability, fast adsorption kinetics, and high removal ratios for 99TcO4- and ReO4- (as a 99TcO4- surrogate) in contaminated water. When used in packed columns, 1-Th-Pd can dynamically capture ReO4- from groundwater. This work provides a new avenue for improving the water stability of MOFs, offering new vistas for the decontamination of aqueous solutions containing 99TcO4- and ReO4-.

Composite Eu@Cd-CP as a fluorescent probe for the detection of some food additives

A transition metal coordination polymer (CP), [Cd(Hdpcp)]n (Cd-CP) was prepared based on 3-(2,4-dicarboxyphenyl)-6-carboxypyridine ligand (H3dpcp), and then its composite Eu@Cd-CP was synthesized by the post-modification through loading Eu3+ ions on Cd-CP. Eu@Cd-CP has outstanding fluorescence stability in aqueous solution with a wide range of pH. Furthermore, Eu@Cd-CP can distinguish sodium salicylate (SS) and sodium dehydroacetate (SA) in some food additives by quenching the characteristic fluorescence of Eu3+ ion. Eu@Cd-CP is the first known CP-based fluorescent probe for selective detection of SS and SA. In addition, the fluorescence mechanisms of discerning above analytes by Eu@Cd-CP have been thoroughly evaluated. It has found that synergistic effect of the dynamic process, photoinduced electron transfer (PET) process, energy absorption competition, and formation of Eu-O bonding interactions in sensing SA lead to the fluorescence quenching of Eu@Cd-CP. The fluorescence response mechanism of Eu@Cd-CP with SA is ascribed to the combination of the dynamic process, PET process, and energy absorption competition. A series of portable devices based on Eu@Cd-CP including fluorescence test strips, lamp beads, and composite films were developed to discern SS and SA via visual changes in luminescence color. This composite material can be potentially used as a multifunctional fluorescent probe for practical applications.

Complexes Based on Zinc and Cadmium for Visible Light-Driven Hydrogen Production

Photocatalytic water decomposition using solar energy is one of the most effective hydrogen production technologies. The development of a structurally stable photocatalyst for hydrogen production without cocatalysts and photosensitizers remains a great challenge. In this paper, complex photocatalyst compounds 1 and 2 with different crystal structures were designed and obtained by connecting the 4'-(2,4-disulfophenyl)-4,2':6',4″-terpyridine organic ligands with Zn(Ac)2·2H2O and CdCO3. These products were used for photocatalytic hydrogen production separately, and the hydrogen production rates of compounds 1 and 2 were 0.66 mol·mol-1·h-1 and 0.12 mol·mol-1·h-1, respectively, without the addition of any cocatalysts and photosensitizers, and their charge separation and transfer processes were verified by PL, time-resolved PL, and photocurrent. Compound 1 was tested in 6 cycles over 18 h and showed high stability and reproducibility.

Leveraging experimental and computational tools for advancing carbon capture adsorbents research

CO2 emissions have been steadily increasing and have been a major contributor for climate change compelling nations to take decisive action fast. The average global temperature could reach 1.5 °C by 2035 which could cause a significant impact on the environment, if the emissions are left unchecked. Several strategies have been explored of which carbon capture is considered the most suitable for faster deployment. Among different carbon capture solutions, adsorption is considered both practical and sustainable for scale-up. But the development of adsorbents that can exhibit satisfactory performance is typically done through the experimental approach. This hit and trial method is costly and time consuming and often success is not guaranteed. Machine learning (ML) and other computational tools offer an alternate to this approach and is accessible to everyone. Often, the research towards materials focuses on maximizing its performance under simulated conditions. The aim of this study is to present a holistic view on progress in material research for carbon capture and the various tools available in this regard. Thus, in this review, we first present a context on the workflow for carbon capture material development before providing various machine learning and computational tools available to support researchers at each stage of the process. The most popular application of ML models is for predicting material performance and recommends that ML approaches can be utilized wherever possible so that experimentations can be focused on the later stages of the research and development.

Atomically Dispersed Metal Catalysts for the Conversion of CO2 into High-Value C2+ Chemicals

The conversion of carbon dioxide (CO2) into value-added chemicals with two or more carbons (C2+) is a promising strategy that cannot only mitigate anthropogenic CO2 emissions but also reduce the excessive dependence on fossil feedstocks. In recent years, atomically dispersed metal catalysts (ADCs), including single-atom catalysts (SACs), dual-atom catalysts (DACs), and single-cluster catalysts (SCCs), emerged as attractive candidates for CO2 fixation reactions due to their unique properties, such as the maximum utilization of active sites, tunable electronic structure, the efficient elucidation of catalytic mechanism, etc. This review provides an overview of significant progress in the synthesis and characterization of ADCs utilized in photocatalytic, electrocatalytic, and thermocatalytic conversion of CO2 toward high-value C2+ compounds. To provide insights for designing efficient ADCs toward the C2+ chemical synthesis originating from CO2, the key factors that influence the catalytic activity and selectivity are highlighted. Finally, the relevant challenges and opportunities are discussed to inspire new ideas for the generation of CO2-based C2+ products over ADCs.

Atomic Molybdenum Nanomaterials for Electrocatalysis

As a sustainable energy technology, electrocatalytic energy conversion requires electrocatalysts, which greatly motivates the exploitation of high-performance electrocatalysts based on nonprecious metals. Molybdenum-based nanomaterials have demonstrated promise as electrocatalysts because of their unique physiochemical and electronic properties. Among them, atomic Mo catalysts, also called Mo-based single-atom catalysts (Mo-SACs), have the most accessible active sites and tunable microenvironments and are thrivingly explored in various electrochemical conversion reactions. A timely review of such rapidly developing topics is necessary to provide guidance for further exploration of optimized Mo-SACs toward electrochemical energy technologies. In this review, recent advances in the synthetic strategies for Mo-SACs are highlighted, focusing on the microenvironment engineering of Mo atoms. Then, the representative achievements of their applications in various electrocatalytic reactions involving the N2, H2O, and CO2 cycles are summarized by combining experimental and computational results. Finally, prospects for the future development of Mo-SACs in electrocatalysis are provided and the key challenges that require further investigation and optimization are highlighted.

Catalytic Nanoparticles in Biomedical Applications: Exploiting Advanced Nanozymes for Therapeutics and Diagnostics

Catalytic nanoparticles (CNPs) as heterogeneous catalyst reveals superior activity due to their physio-chemical features, such as high surface-to-volume ratio and unique optical, electric, and magnetic properties. The CNPs, based on their physio-chemical nature, can either increase the reactive oxygen species (ROS) level for tumor and antibacterial therapy or eliminate the ROS for cytoprotection, anti-inflammation, and anti-aging. In addition, the catalytic activity of nanozymes can specifically trigger a specific reaction accompanied by the optical feature change, presenting the feasibility of biosensor and bioimaging applications. Undoubtedly, CNPs play a pivotal role in pushing the evolution of technologies in medical and clinical fields, and advanced strategies and nanomaterials rely on the input of chemical experts to develop. Herein, a systematic and comprehensive review of the challenges and recent development of CNPs for biomedical applications is presented from the viewpoint of advanced nanomaterial with unique catalytic activity and additional functions. Furthermore, the biosafety issue of applying biodegradable and non-biodegradable nanozymes and future perspectives are critically discussed to guide a promising direction in developing span-new nanozymes and more intelligent strategies for overcoming the current clinical limitations.

Recent Advances in Engineering Fe-N-C Catalysts for Oxygen Electrocatalysis in Zn-Air Batteries

Fe-N-C single-atom catalysts (SACs) have emerged as one of the most promising candidates for oxygen electrocatalysis due to their maximized atom utilization efficiency, high intrinsic activity, and strong metal-support interaction. Significant progress has been made in engineering Fe-N-C SACs for oxygen electrocatalysis in Zn-air batteries (ZABs). This review provides a comprehensive overview of the recent advancements in Fe-N-C SACs, with a special focus on effective engineering strategies, their performance in oxygen electrocatalysis, and their potential applications in ZABs. The review also discusses the key challenges and future directions in the development of Fe-N-C SACs for efficient and durable oxygen electrocatalysis in ZABs. This review aims to offer valuable insights into the current state of research in this field and to guide future efforts in the development of advanced oxygen electrocatalysts for ZABs.

Metal-Organic Frameworks for Electrocatalytic CO2 Reduction: From Catalytic Site Design to Microenvironment Modulation

The electrochemical reduction of CO2 to high-value carbon-based chemicals provides a sustainable approach to achieving an artificial carbon cycle. In the decade, metal-organic frameworks (MOFs), a kind of porous crystalline porous materials featuring well-defined structures, large surface area, high porosity, diverse components, easy tailorability, and controllable morphology, have attracted considerable research attention, serving as electrocatalysts to drive CO2 reduction. In this review, the reaction mechanisms of electrochemical CO2 reduction and the structure/component advantages of MOFs meeting the requirements of electrocatalysts for CO2 reduction are analyzed. After that, the representative progress for the precise fabrication of MOF-based electrocatalysts for CO2 reduction, focusing on catalytic site design and microenvironment modulation, are systemically summarized. Furthermore, the emerging applications and promising research for more practical scenarios related to electrochemical CO2 conversion are specifically proposed. Finally, the remaining challenges and future outlook of MOFs for electrochemical CO2 reduction are further discussed.

A review on synthesis of MOF-derived carbon composites: innovations in electrochemical, environmental and electrocatalytic technologies

Carbon composites derived from Metal-Organic Frameworks (MOFs) have shown great promise as multipurpose materials for a range of electrochemical and environmental applications. Since carbon-based nanomaterials exhibit intriguing features, they have been widely exploited as catalysts or catalysts supports in the chemical industry or for energy or environmental applications. To improve the catalytic performance of carbon-based materials, high surface areas, variable porosity, and functionalization are thought to be essential. This study offers a thorough summary of the most recent developments in MOF-derived carbon composite synthesis techniques, emphasizing innovative approaches that improve the structural and functional characteristics of the materials. Their uses in electrochemical technologies, such as energy conversion and storage, and their function in environmental electrocatalysis for water splitting and pollutant degradation are also included in the debate. This review seeks to clarify the revolutionary effect of carbon composites formed from MOFs on sustainable technology solutions by analyzing current research trends and innovations, opening the door for further advancements in this rapidly evolving sector.

Exploring the Dynamics of Charge Transfer in Photocatalysis: Applications of Femtosecond Transient Absorption Spectroscopy

Artificial photocatalytic energy conversion is a very interesting strategy to solve energy crises and environmental problems by directly collecting solar energy, but low photocatalytic conversion efficiency is a bottleneck that restricts the practical application of photocatalytic reactions. The key issue is that the photo-generated charge separation process spans a huge spatio-temporal scale from femtoseconds to seconds, and involves complex physical processes from microscopic atoms to macroscopic materials. Femtosecond transient absorption (fs-TA) spectroscopy is a powerful tool for studying electron transfer paths in photogenerated carrier dynamics of photocatalysts. By extracting the attenuation characteristics of the spectra, the quenching path and lifetimes of carriers can be simulated on femtosecond and picosecond time scales. This paper introduces the principle of transient absorption, typical dynamic processes and the application of femtosecond transient absorption spectroscopy in photocatalysis, and summarizes the bottlenecks faced by ultrafast spectroscopy in photocatalytic applications, as well as future research directions and solutions. This will provide inspiration for understanding the charge transfer mechanism of photocatalytic processes.

Hierarchically Micro-, Meso-, and Macro-Porous MOF Nanosystems for Localized Cross-Scale Dual-Biomolecule Loading and Guest-Carrier Cooperative Anticancer Therapy

Mass transfer of bulky molecules, e.g., bioenzymes, particularly for cross-scale multibiomolecules, imposes serious challenges for microporous metal-organic frameworks (MOFs). Here, we create a hierarchically porous MOF heterostructure featuring highly region-ordered micro-, meso-, and macro-pores by growing a microporous ZIF-8 shell onto a hollow Prussian blue core through an epitaxial growth strategy. This allows for localized loading of large bioenzyme glucose oxidase (GOx) and small drug 5-fluorouracil (5-FU) within specific pores simultaneously and triggers unique guest-carrier cooperative anticancer capabilities. The stable ZIF-8 outer layer effectively blocks the core pores, preventing the undesired leakage of GOx into normal tissues. The acidity-induced ZIF-8 degradation gradually releases Zn2+ and loaded 5-FU for chemotherapy under acidic tumor microenvironments. With the loss of the shielding effect of the ZIF-8 coating, the released GOx depletes intratumoral glucose (Glu) for starvation therapy. Notably, an accelerated cascade reaction occurs between ZIF-8 decomposition and GOx release, facilitated by the modulator factor of Glu. This culminates in the realization of synergistic cancer therapy, as comprehensively demonstrated by in vitro and in vivo experiments, as well as transcriptome sequencing analyses. Our work not only introduces a hierarchically porous MOF heterostructure with highly region-ordered pores but also provides a perspective for guest-carrier cooperative anticancer therapy.

An n-type semiconducting diazaporphyrin-based hydrogen-bonded organic framework

Significant effort has been devoted to the development of materials that combine high electrical conductivity and permanent porosity. This paper discloses a diazaporphyrin-based hydrogen-bonded organic framework (HOF) with porosity and n-type semiconductivity. A 5,15-diazaporphyrin Ni(ii) complex with carboxyphenyl groups at the meso positions afforded a HOF due to hydrogen-bonding interactions between the carboxy groups and meso-nitrogen atoms. The thermal and chemical stabilities of the HOF were examined using powder X-ray diffraction analysis, and the charge-carrier mobility was determined to be 2.0 × 10-7 m2 V-1 s-1 using the flash-photolysis time-resolved microwave conductivity (FP-TRMC) method. An analogous diazaporphyrin, which does not form a HOF, exhibited mobility that was 20 times lower. The results presented herein highlight the crucial role of hydrogen-bonding networks in achieving conductive pathways that can tolerate thermal perturbation.

Monodentate Phosphinoamine Nickel Complex Supported on a Metal-Organic Framework for High-Performance Ethylene Dimerization

Ethylene dimerization is an efficient industrial chemical process to produce 1-butene, with demanding selectivity and activity requirements on new catalytic systems. Herein, a series of monodentate phosphinoamine-nickel complexes immobilized on UiO-66 are described for ethylene dimerization. These catalysts display extensive molecular tunability of the ligand similar to organometallic catalysis, while maintaining the high stability attributed to the metal-organic framework (MOF) scaffold. The highly flexible postsynthetic modification method enables this study to prepare MOFs functionalized with five different substituted phosphines and 3 N-containing ligands and identify the optimal catalyst UiO-66-L5-NiCl2 with isopropyl substituted nickel mono-phosphinoamine complex. This catalyst shows a remarkable activity and selectivity with a TOF of 29 000 (molethyl/molNi/h) and 99% selectivity for 1-butene under ethylene pressure of 15 bar. The catalyst is also applicable for continuous production in the packed column micro-reactor with a TON of 72 000 (molethyl/molNi). The mechanistic insight for the ethylene oligomerization has been examined by density functional theory (DFT) calculations. The calculated energy profiles for homogeneous complexes and truncated MOF models reveal varying rate-determining step as β-hydrogen elimination and migratory insertion, respectively. The activation barrier of UiO-66-L5-NiCl2 is lower than other systems, possibly due to the restriction effect caused by clusters and ligands. A comprehensive analysis of the structural parameters of catalysts shows that the cone angle as steric descriptor and butene desorption energy as thermodynamic descriptor can be applied to estimate the reactivity turnover frequency (TOF) with the optimum for UiO-66-L5-NiCl2. This work represents the systematic optimization of ligand effect through combination of experimental and theoretical data and presents a proof-of-concept for ethylene dimerization catalyst through simple heterogenization of organometallic catalyst on MOF.