Visible-light-switched electron transfer over single porphyrin-metal atom center for highly selective electroreduction of carbon dioxide

Optical Phenomena in Molecule-Based Magnetic Materials

Since the last century, we have witnessed the development of molecular magnetism which deals with magnetic materials based on molecular species, i.e., organic radicals and metal complexes. Among them, the broadest attention was devoted to molecule-based ferro-/ferrimagnets, spin transition materials, including those exploring electron transfer, molecular nanomagnets, such as single-molecule magnets (SMMs), molecular qubits, and stimuli-responsive magnetic materials. Their physical properties open the application horizons in sensors, data storage, spintronics, and quantum computation. It was found that various optical phenomena, such as thermochromism, photoswitching of magnetic and optical characteristics, luminescence, nonlinear optical and chiroptical effects, as well as optical responsivity to external stimuli, can be implemented into molecule-based magnetic materials. Moreover, the fruitful interactions of these optical effects with magnetism in molecule-based materials can provide new physical cross-effects and multifunctionality, enriching the applications in optical, electronic, and magnetic devices. This Review aims to show the scope of optical phenomena generated in molecule-based magnetic materials, including the recent advances in such areas as high-temperature photomagnetism, optical thermometry utilizing SMMs, optical addressability of molecular qubits, magneto-chiral dichroism, and opto-magneto-electric multifunctionality. These findings are discussed in the context of the types of optical phenomena accessible for various classes of molecule-based magnetic materials.

Single Zn Atoms with Acetate-Anion-Enabled Asymmetric Coordination for Efficient H2 O2 Photosynthesis

Exploring unique single-atom sites capable of efficiently reducing O2 to H2 O2 while being inert to H2 O2 decomposition under light conditions is significant for H2 O2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn-N3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N4 sites when sulfate (SO4 ) is adopted (CN/Zn-SO4 ). Both experimental and theoretical investigations demonstrate that the Zn-N3 O moiety exhibits higher intrinsic activity for O2 reduction to H2 O2 than the Zn-N4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H2 O2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H2 O2 production activity under visible light irradiation.

Anchoring of Metal Complexes on Au25 Nanocluster for Enhanced Photocoupled Electrocatalytic CO2 Reduction

Atomically precise Au nanoclusters (NCs) with discrete energy levels can be used as photosensitizers for CO2 reduction. However, tight ligand capping of Au NCs hinders CO2 adsorption on its active sites. Here, a new hybrid material is obtained by anchoring of thiol functionalized terpyridine metal complexes (metal=Ru, Ni, Fe, Co) on Au NCs by ligand exchange reactions (LERs). The anchoring of Ru and Ni complexes on Au25 NC (Au25 -Ru and Au25 -Ni) leads to adequate CO2 to CO conversion for photocoupled electrocatalytic CO2 reduction (PECR) in terms of high selectivity, with Faradaic efficiency of CO (FECO ) exceeding 90 % in a wide potential range, remarkable activity (CO production rate up to two times higher than that for pristine Au25 PET18 ) and extremely large turnover frequencies (TOFs, 63012 h-1 at -0.97 V for Au25 -Ru and 69989 h-1 at -1.07 V vs. RHE for Au25 -Ni). Moreover, PECR stability test indicates the excellent long-term stability of the modified NCs in contrast with pristine Au NCs. The present approach offers a novel strategy to enhance PECR activity and selectivity, as well as to improve the stability of Au NCs under light illumination, which paves the way for highly active and stable Au NCs catalysts.

Porphyrin-based covalent organic polymers with customizable photoresponses for photodynamic inactivation of bacteria

Porphyrin-linked covalent organic polymers (COPs) provide a reliable photocatalytic platform, while photodynamic inactivation (PDI) induced by reliable porphyrin-based COPs is considered to be an effective method to resist microbial contamination. Herein, three tunable porphyrin-based covalent organic polymers (H2-Por-COPs, OH-Por-COPs, and Zn-Por-COPs) are designed and employed for the PDI of Staphylococcus aureus and Escherichia coli under visible light illumination. Interestingly, singlet oxygen (1O2) generation by the Por-COPs can be manipulated via intramolecular regulation with the order Zn-Por-COP > OH-Por-COP > H2-Por-COP. With rationally tune, the Zn-Por-COP demonstrated remarkable antibacterial activity against Staphylococcus aureus (kill percentage 99.65 % ± 0.24 %) and Escherichia coli (kill percentage 97.25 % ± 1.78 %) in only 15 min under visible-light irradiation. Density functional theory (DFT) calculations and photophysical tests showed that the presence of electron-donating -OH groups on the aromatic linkers and Zn2+ ions in porphyrin units narrowed the HOMO-LUMO gap, enhancing both light absorption, intersystem crossing (ISC) and 1O2 generation for more efficient bacteria inactivation. This work can be applied to efficiently screen suitable photosensitizers and provides a rational regulatory strategy for PDI of pathogenic bacteria.

CO2 electrocatalytic reduction to ethylene and its application outlook in food science

The efficient conversion of CO2 is considered to be an important step toward carbon emissions peak and carbon neutrality. Presently, great efforts have been devoted to the study of efficient nanocatalysts, electrolytic cell, and electrolytes to achieve high reactivity and selectivity in the electrochemical reduction of CO2 to mono- and multi-carbon (C2+) compounds. However, there are very few reviews focusing on highly reactive and selective ethylene production and application in the field of electrochemical carbon dioxide reduction reaction (CO2RR). Ethylene is a class of multi-carbon compounds that are widely applied in industrial, ecological, and agricultural fields. This review focuses especially on the convertibility of CO2 reduction to generate ethylene technology in practical applications and provides a detailed summary of the latest technologies for the efficient production of ethylene by CO2RR and suggests the potential application of CO2RR systems in food science to further expand the application market of CO2RR for ethylene production.

A novel magneto-mediated electrochemical biosensor integrated DNAzyme motor and hollow nanobox-like Pt@Ni-Co electrocatalyst as dual signal amplifiers for vanilla detection

Herein, a novel magneto-mediated electrochemical aptasensor using the signal amplification technologies of DNAzyme motor and electrocatalyst for vanilla (VAN) detection was fabricated. The D/B duplex, formed by the DNAzyme motor that was each silenced by a blocker, and hairpin DNA1 (H1) containing adenosine ribonucleotide (rA) site were tethered on the sites of the gold nanoparticles@hollow porphyrinic-Metal-organic framework/polyethyleneimine-reduced graphene oxide (AuHPCN-222/PEI-rGO)-modified gold electrode (AuE). Then, after homogeneous and specific recognition in the presence of the VAN, trigger DNA was released and enriched by magnetic separation technique and introduced to the sensing platform to activate the DNAzyme motor, which efficiently improved target recognition capability and avoided the obstacle of multiple DNA strands tangling. More interestingly, the activated DNAzyme motor could repeatedly bind to and cleave H1 in the presence of Mg2+, leading to the exposure of a plethora of capture probes. The thionine (Thi) functionalized hairpin DNA2 (H2)-Pt@Ni-Co as signal probes could hybridize with capture probes. Additionally, the Pt@Ni-Co electrocatalysts presented catalytic activity towards Thi to obtain stronger electrochemical signals. VAN with concentrations ranging from 1 × 10-6 to 10 μM was determined and a detection limit was down to 0.15 pM. The designed electrochemical sensor was highly selective with specificity, stability, reproducibility, and reliable capability for monitoring the VAN in real samples.

Photocoupled Electroreduction of CO2 over Photosensitizer-Decorated Covalent Organic Frameworks

Introducing an external visible-light field would be a promising strategy to improve the activity of the electrocatalytic CO2 reduction reaction (CO2RR), but it still remains a challenge due to the short excited-state lifetime of active sites. Herein, Ru(bpy)3Cl2 struts as powerful photosensitive donors were immobilized into the backbones of Co-porphyrin-based covalent organic frameworks (named Co-Bpy-COF-Rux, x is the molar ratio of Ru and Co species, x = 1/2 and 2/3) via coordination bonds, for the photo-coupled CO2RR to produce CO. The optimal Co-Bpy-COF-Ru1/2 displays a high CO Faradaic efficiency of 96.7% at -0.7 V vs reversible hydrogen electrode (RHE) and a CO partial current density of 16.27 mA cm-2 at -1.1 V vs RHE under the assistance of light, both of which were far surpassing the values observed in the dark. The significantly enhanced activity is mainly attributed to the incorporation of a Ru(bpy)3Cl2 donor with long excited-state lifetime and concomitantly giant built-in electric field in Co-Bpy-COF-Ru1/2, which efficiently accelerate the photo-induced electron transfer from Ru(bpy)3Cl2 to the cobalt-porphyrin under the external light. Thus, the cobalt-porphyrin active sites have a longer excited-state lifetime to lower the rate-determining steps' energy occurring during the actual photo-coupled electrocatalytic CO2RR process. This is the first work of porphyrin-based COFs for photo-coupled CO2RR, opening a new frontier for the construction of efficient photo-coupled electrocatalysts.

Covalent Organic Frameworks for Energy Conversion in Photocatalysis

Intensifying energy crises and severe environmental issues have led to the discovery of renewable energy sources, sustainable energy conversion, and storage technologies. Photocatalysis is a green technology that converts eco-friendly solar energy into high-energy chemicals. Covalent organic frameworks (COFs) are porous materials constructed by covalent bonds that show promising potential for converting solar energy into chemicals owing to their pre-designable structures, high crystallinity, and porosity. Herein, we highlight recent progress in the synthesis of COF-based photocatalysts and their applications in water splitting, CO2 reduction, and H2 O2 production. The challenges and future opportunities for the rational design of COFs for advanced photocatalysts are discussed. This Review is expected to promote further development of COFs toward photocatalysis.

Enhanced the Efficiency of Electrocatalytic CO2 -to-CO Conversion by Cd Species Anchored into Metal-Organic Framework

Metal-organic frameworks (MOFs) as a promising platform for electrocatalytic CO2 conversion are still restricted by the low efficiency or unsatisfied selectivity for desired products. Herein, zirconium-based porphyrinic MOF hollow nanotubes with Cd sites (Cd-PCN-222HTs) are reported for electrocatalytic CO2 -to-CO conversion. The dispersed Cd species are anchored in PCN-222HTs and coordinated by N atoms of porphyrin structures. It is discovered that Cd-PCN-222HTs have glorious electrocatalytic activity for selective CO production in ionic liquid-water (H2 O)-acetonitrile (MeCN) electrolyte. The CO Faradaic efficiency (FECO ) of >80% could be maintained in a wide potential range from -2.0 to -2.4 V versus Ag/Ag+ , and the maximum current density could reach 68.0 mA cm-2 at -2.4 V versus Ag/Ag+ with a satisfied turnover frequency of 26 220 h-1 . The enhanced efficiency of electrocatalytic CO2 conversion of Cd-PCN-222HTs is closely related to its hollow structure, anchored Cd species, and good synergistic effect with electrolyte. The density functional theory calculations indicate that the dispersed Cd sites anchored in PCN-222HTs not only favor the formation of *COOH intermediate but also hinder the hydrogen evolution reaction, resulting in high activity of electrocatalytic CO2 -to-CO conversion.

Progress in photocatalytic CO2 reduction based on single-atom catalysts

Reduced CO₂ emissions, conversion, and reuse are critical steps toward carbon peaking and carbon neutrality. Converting CO₂ into high-value carbon-containing compounds or fuels may effectively address the energy shortage and environmental issues, which is consistent with the notion of sustainable development. Photocatalytic CO₂ reduction processes have become one of the research focuses, where single-atom catalysts have demonstrated significant benefits owing to their excellent percentage of atom utilization. However, among the crucial challenges confronting contemporary research is the production of efficient, low-cost, and durable photocatalysts. In this paper, we offer a comprehensive overview of the study growth on single-atom catalysts for photocatalytic CO₂ reduction reactions, describe several techniques for preparing single-atom catalysts, and discuss the advantages and disadvantages of single-atom catalysts and present the study findings of three single-atom photocatalysts with TiO₂, g-C₃N₄ and MOFs materials as carriers based on the interaction between single atoms and carriers, and finally provide an outlook on the innovation of photocatalytic CO₂ reduction reactions.

Imaging Photon-Induced Near-Field Distributions of a Plasmonic, Self-Assembled Vesicle by a Laser-Integrated Electron Microscope

Plasmonic polymeric nanoassemblies offer valuable opportunities in photoconversion applications. Localized surface plasmon mechanisms behind such nanoassemblies govern their functionalities under light illumination. However, an in-depth investigation at the single nanoparticle (NP) level is still challenging, especially when the buried interface is involved, due to the availability of suitable techniques. Here, we synthesized an anisotropic heterodimer composed of a self-assembled polymer vesicle (THPG) capped with a single gold NP, enabling an 8-fold enhancement in hydrogen generation compared to the nonplasmonic THPG vesicle. We explored the anisotropic heterodimer at the single particle level by employing advanced transmission electron microscopes, including one equipped with a femtosecond pulsed laser, which allows us to visualize the polarization- and frequency-dependent distribution of the enhanced electric near fields at the vicinity of Au cap and Au-polymer interface. These elaborated fundamental findings may guide designing new hybrid nanostructures tailored for plasmon-related applications.

Porphyrin-Based Covalent Organic Frameworks Anchoring Au Single Atoms for Photocatalytic Nitrogen Fixation

The development of efficient photocatalysts for N₂ fixation to produce NH₃ under ambient conditions remains a great challenge. Since covalent organic frameworks (COFs) possess predesignable chemical structures, good crystallinity, and high porosity, it is highly significant to explore their potential for photocatalytic nitrogen conversion. Herein, we report a series of isostructural porphyrin-based COFs loaded with Au single atoms (COFX-Au, X = 1-5) for photocatalytic N₂ fixation. The porphyrin building blocks act as the docking sites to immobilize Au single atoms as well as light-harvesting antennae. The microenvironment of the Au catalytic center is precisely tuned by controlling the functional groups at the proximal and distal positions of porphyrin units. As a result, COF1-Au decorated with strong electron-withdrawing groups exhibits a high activity toward NH₃ production with rates of 333.0 ± 22.4 μmol g^-1 h^-1 and 37.0 ± 2.5 mmol g_Au^-1 h^-1, which are 2.8- and 171-fold higher than that of COF4-Au decorated with electron-donating functional groups and a porphyrin-Au molecular catalyst, respectively. The NH₃ production rates could be further increased to 427.9 ± 18.7 μmol g^-1 h^-1 and 61.1 ± 2.7 mmol g_Au^-1 h^-1 under the catalysis of COF5-Au featuring two different kinds of strong electron-withdrawing groups. The structure-activity relationship analysis reveals that the introduction of electron-withdrawing groups facilitates the separation and transportation of photogenerated electrons within the entire framework. This work manifests that the structures and optoelectronic properties of COF-based photocatalysts can be finely tuned through a rational predesign at the molecular level, thus leading to superior NH₃ evolution.

Role of the Support Effects in Single-Atom Catalysts

In recent years, single-atom catalysts (SACs) have received a significant amount of attention due to their high atomic utilization, low cost, high reaction activity, and selectivity for multiple catalytic reactions. Unfortunately, the high surface free energy of single atoms leads them easily migrated and aggregated. Therefore, support materials play an important role in the preparation and catalytic performance of SACs. Aiming at understanding the relationship between support materials and the catalytic performance of SACs, the support effects in SACs are introduced and reviewed herein. Moreover, special emphasis is placed on exploring the influence of the type and structure of supports on SAC catalytic performance through advanced characterization and theoretical research. Future research directions for support materials are also proposed, providing some insight into the design of SACs with high efficiency and high loading.

Gold single-atoms confined at the CeOx-TiO2interfaces with enhanced low-temperature activity toward CO oxidation

We use CeO_x-TiO₂hetero-interfaces generated on the surface of CeO_x-TiO₂hybrid oxide supporting powders to stabilize Au single-atoms (SAs) with excellent low-temperature activity toward CO oxidation. Based on intriguing density functional theory calculation results on the preferential formation of Au-SAs at the CeO_x-TiO₂interfaces and the high activity of Au-SAs toward the Mars-van Krevelen type CO oxidation, we synthesized a Au/CeO_x-TiO₂(ACT) catalyst with 0.05 wt.% of Au content. The Au-SAs stabilized at the CeO_x-TiO₂interfaces by electronic coupling between Au and Ce showed improved low-temperature CO oxidation activity than the conventional Au/TiO₂control group catalyst. However, the light-off profile of ACT showed that the early activated Au-SAs are not vigorously participating in CO oxidation. The large portion of the positive effect on the overall catalytic activity from the low activation energy barrier of ACT was retarded by the negative impact from the decreasing active site density at high temperatures. We anticipate that the low-temperature activity and high-temperature stability of Au-SAs that stand against each other can be optimized by controlling the electronic coupling strength between Au-SAs and oxide clusters at the Au-oxide-TiO₂interfaces. Our results show that atomic-precision interface modulation could fine-tune the catalytic activity and stability of Au-SAs.

In situ Cu single atoms anchoring on MOF-derived porous TiO2 for the efficient separation of photon-generated carriers and photocatalytic H2 evolution

Single atom catalysts (SACs) have an extremely high atom utilization and distinctive structures and properties in the field of photocatalysis. However, the premise of conducting scientific research and applications is still the stability and catalytic activity of single atoms on suitable substrates. Metal organic frameworks (MOFs), as one of the most suitable single-atom substrates, have tunable internal structures, unsaturated coordination bonds, and high specific surface areas. In this work, Ti-based MOF, MIL-125, was adopted as the precursor to prepare mesoporous Cu-loaded TiO₂. During the synthesis of MIL-125, a Cu source was added, and Cu atoms were fixed by partly replacing Ti atoms in the Ti-O octahedron to coordinate with O atoms, resulting in a good dispersity, good stability and high loading amount. Experimental investigations demonstrated that dispersed Cu single atoms act as reaction centres, besides being able to accelerate the transfer of photoelectrons. Under simulated sunlight, the H₂ evolution rate of the optimum Cu-TiO₂ sample reaches 17.77 mmol g^-1 h^-1, nearly 101 times higher than that of the pure mesoporous TiO₂. The apparent quantum efficiency (AQE) is 20.15% under 365 nm irradiation. This research opens a new thinking to preparing high stability and high activity single atom photocatalysts.

Advances in Biomimetic Photoelectrocatalytic Reduction of Carbon Dioxide

Emerging photoelectrocatalysis (PEC) systems synergize the advantages of electrocatalysis (EC) and photocatalysis (PC) and are considered a green and efficient approach to CO₂ conversion. However, improving the selectivity and conversion rate remains a major challenge. Strategies mimicking natural photosynthesis provide a prospective way to convert CO₂ with high efficiency. Herein, several typical strategies are described for constructing biomimetic photoelectric functional interfaces; such interfaces include metal cocatalysts/semiconductors, small molecules/semiconductors, molecular catalysts/semiconductors, MOFs/semiconductors, and microorganisms/semiconductors. The biomimetic PEC interface must have enhanced CO₂ adsorption capacity, preferentially activate CO₂ , and have an efficient conversion ability; with these properties, it can activate CO bonds effectively and promote electron transfer and CC coupling to convert CO₂ to single-carbon or multicarbon products. Interfacial electron transfer and proton coupling on the biomimetic PEC interface are also discussed to clarify the mechanism of CO₂ reduction. Finally, the existing challenges and perspectives for biomimetic photoelectrocatalytic CO₂ reduction are presented.

V-Porphyrins Encapsulated or Supported on Siliceous Materials: Synthesis, Characterization, and Photoelectrochemical Properties

Metalloporphyrin-containing mesoporous materials, named VTPP@SBA, were prepared via a simple anchoring of vanadyl porphyrin (5,10,15,20-Tetraphenyl-21H,23H-porphine vanadium(IV) oxide) through a SBA-15-type mesoporous material. For comparison, vanadyl porphyrin was also impregnated on SiO₂ (VTPP/SiO₂). The characterization results of catalysts by XRD, FTIR, DR-UV-vis, and EPR confirm the incorporation of vanadyl porphyrin within the mesoporous SBA-15. These catalysts have also been studied using electrochemical and photoelectrochemical methods. Impedance measurements confirmed that supporting the porphyrin in silica improved the electrical conductivity of samples. In fact, when using mesoporous silica, current densities associated with oxidation/reduction processes appreciably increased, implying an enhancement in charge transfer processes and, therefore, in electrochemical performance. All samples presented n-type semiconductivity and provided an interesting photoelectrocatalytic response upon illumination, especially silica-supported porphyrins. This is the first time that V-porphyrin-derived materials have been tested for photoelectrochemical applications, showing good potential for this use.

Photocatalytic Carbon Dioxide Conversion by Structurally and Materially Modified Titanium Dioxide Nanostructures

TiO₂ has aroused considerable attentions as a promising photocatalytic material for decades due to its superior material properties in several fields such as energy and environment. However, the main dilemmas are its wide bandgap (3–3.2 eV), that restricts the light absorption in limited light wavelength region, and the comparatively high charge carrier recombination rate of TiO₂, is a hurdle for efficient photocatalytic CO₂ conversion. To tackle these problems, lots of researches have been implemented relating to structural and material modification to improve their material, optical, and electrical properties for more efficient photocatalytic CO₂ conversion. Recent studies illustrate that crystal facet engineering could broaden the performance of the photocatalysts. As same as for nanostructures which have advantages such as improved light absorption, high surface area, directional charge transport, and efficient charge separation. Moreover, strategies such as doping, junction formation, and hydrogenation have resulted in a promoted photocatalytic performance. Such strategies can markedly change the electronic structure that lies behind the enhancement of the solar spectrum harnessing. In this review, we summarize the works that have been carried out for the enhancement of photocatalytic CO₂ conversion by material and structural modification of TiO₂ and TiO₂-based photocatalytic system. Moreover, we discuss several strategies for synthesis and design of TiO₂ photocatalysts for efficient CO₂ conversion by nanostructure, structure design of photocatalysts, and material modification.

Accurate Determination of Adsorption-Energy Differences of Metalloporphyrins on Rutile TiO2(110) 1 × 1

Understanding the adsorption of organic molecules on surfaces is of essential importance for many applications. Adsorption energies are typically measured using temperature-programmed desorption. However, for large organic molecules, often only desorption of the multilayers is possible, while the bottom monolayer in direct contact to the surface cannot be desorbed without decomposition. Nevertheless, the adsorption energies of these directly adsorbed molecules are the ones of the most interest. We use a layer-exchange process investigated with X-ray photoelectron spectroscopy to compare the relative adsorption energies of several metalated tetraphenylporphyrins on rutile TiO₂(110) 1 × 1. We deposit a mixture of two different molecules, one on top of the other, and slowly anneal above their multilayer desorption temperature. During the slow heating, the molecules begin to diffuse between the layers and the molecules with the stronger interaction with the surface displace the weaker-interacting molecules from the surface and push them into the multilayer. The multilayers eventually desorb, leaving behind a monolayer of strongly interacting molecules. From the ratio of the two different porphyrin molecules in the residual monolayer and the desorbed multilayer, we can calculate the equilibrium constant of the layer-exchange process and thereby the difference in adsorption energy between the two different porphyrin molecules.

Porphyrins and phthalocyanines as biomimetic tools for photocatalytic H2 production and CO2 reduction

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H₂ is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO₂ into chemical fuels can reduce the CO₂ emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H₂ production and CO₂ reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application.

Reductive Upgrading of Biomass-Based Levulinic Acid to γ-Valerolactone Over Ru-Based Single-Atom Catalysts

With the great adjustment of world industrialization and the continuous improvement of energy consumption requirements, the selective conversion of biomass-based platform molecules to high-value chemicals and biofuels has become one of the most important topics of current research. Catalysis is an essential approach to achieve energy-chemical conversion through the “bond breaking-bond formation” principle, which opens a broad world for the energy sector. Single-atom catalysts (SACs) are a new frontier in the field of catalysis in recent years, and exciting achievements have been made in biomass energy chemistry. This mini-review focuses on catalytic conversion of biomass-based levulinic acid (LA) to γ-valerolactone (GVL) over SACs. The current challenges and future development directions of SACs-mediated catalytic upgrading of biomass-based LA to produce value-added GVL, and the preparation and characterization of SACs are analyzed and summarized, aiming to provide theoretical guidance for further development of this emerging field.

Ultrahigh Photocatalytic CO2 Reduction Efficiency and Selectivity Manipulation by Single-Tungsten-Atom Oxide at the Atomic Step of TiO2

The photocatalytic CO₂ reduction reaction is a sustainable route to the direct conversion of greenhouse gases into chemicals without additional energy consumption. Given the vast amount of greenhouse gas, numerous efforts have been devoted to developing inorganic photocatalysts, e.g., titanium dioxide (TiO₂ ), due to their stability, low cost, and environmentally friendly properties. However, a more efficient TiO₂ photocatalyst without noble metals is highly desirable for CO₂ reduction, and it is both difficult and urgent to produce selectively valuable compounds. Here, a novel "single-atom site at the atomic step" strategy is developed by anchoring a single tungsten (W) atom site with oxygen-coordination at the intrinsic steps of classic TiO₂ nanoparticles. The composition of active sites for CO₂ reduction can be controlled by tuning the additional W⁵⁺ to form W⁵⁺ -O-Ti³⁺ sites, resulting in both significant CO₂ reduction efficiency with 60.6 μmol g^{- 1} h^{- 1} and selectivity for methane (CH₄ ) over carbon monoxide (CO), which exceeds those of pristine TiO₂ by more than one order of magnitude. The mechanism relies on the accurate control of the single-atom sites at step with 22.8% coverage of surface sites and the subsequent excellent electron-hole separation along with the favorable adsorption-desorption of intermediates at the sites.

Tailoring Layer Number of 2D Porphyrin-Based MOFs Towards Photocoupled Electroreduction of CO2

Inspired by the success of graphene, a series of single- or few-layer 2D materials have been developed and applied in the past decade. Here, the successful preparation of monolayer and bilayer 2D porphyrin-based metal-organic frameworks (MOFs) by a facile solvothermal method is reported. The structure transition from monolayer to bilayer drives distinct electronic properties and restructuring behaviors, which finally results in distinct catalytic pathways towards CO₂ electrocatalysis. The monolayer favors CO₂ -to-C₂ pathway due to the restructuring of CuO₄ sites, while CO and HCOO^- are the major products over the bilayer. In photocoupled electrocatalysis, the Faradaic efficiency (FE) of the C₂ compounds shows a nearly fourfold increase on the monolayer than that under dark conditions (FE_C2 increases from 11.9% to 41.1% at -1.4 V). For comparison, the light field plays a negligible effect on the bilayer. The light-induced selectivity optimization is investigated by experimental characterization and density functional theory (DFT) calculations. This work opens up a novel possibility to tune the selectivity of carbon products just by tailoring the layer number of the 2D material.

Nanoarchitectonics of Metal-Free Porous Polyketone as Photocatalytic Assemblies for Artificial Photosynthesis

The main component of natural gas is methane, whose combustion contributes to global warming. As such, sustainable, energy-efficient, nonfossil-based methane production is needed to satisfy current energy demands and chemical feedstocks. In this article, we have constructed a metal-free porous polyketone (TPA-DPA PPK) with donor-acceptor (D-A) groups with an extensive π-conjugation by facile Friedel-Crafts acylation reaction between triphenylamine (TPA) and pyridine-2,6-dicarbonyl dichloride (DPA). TPA-DPA PPK is a metal-free catalyst for visible-light-driven CO₂ photoreduction to CH₄, which can be used as a solar fuel in the absence of any cocatalyst and sacrificial agent. CH₄ production (152.65 ppm g^-1) is ∼5 times greater than that of g-C₃N₄ under the same test conditions. Charge-density difference plots from excited-state time-dependent density functional theory (TD-DFT) calculations indicate a depletion and accumulation of charge density among the donor/acceptor functional groups upon photoexcitation. Most notably, binding energies from DFT demonstrate that H₂O is more strongly bound with the pyridinic nitrogen group than CO_2, which shed insight into mechanistic pathways for photocatalytic CO₂ reduction.

Loading Single-Ni Atoms on Assembled Hollow N-Rich Carbon Plates for Efficient CO2 Electroreduction

The rational design of catalysts' spatial structure is vitally important to boost catalytic performance through exposing the active sites, enhancing the mass transfer, and confining the reactants. Herein, a dual-linker zeolitic tetrazolate framework-engaged strategy is developed to construct assembled hollow plates (AHP) of N-rich carbon (NC), which is loaded with single-Ni atoms to form a highly efficient electrocatalyst (designated as Ni-NC(AHP)). In the carbonization process, the thermally unstable linker (5-aminotetrazole) serves as the self-sacrificial template and the other linker (2-methylimidazole) mainly serves as the carbon and nitrogen source to form hollow NC matrix. The formed Ni-NC(AHP) catalyst possesses enhanced mesoporosity and more available surface area, thus promoting mass transport and affording abundant accessible single-Ni sites. These features contribute to remarkable performance for electrochemical CO₂ reduction with exceptionally high selectivity of nearly 100% towards CO in a wide potential range and dramatically enhanced CO partial current density.

A single-atom Cu-N2 catalyst eliminates oxygen interference for electrochemical sensing of hydrogen peroxide in a living animal brain

Hydrogen peroxide (H₂O₂) plays essential roles in various physiological and pathological processes. The electrochemical hydrogen peroxide reduction reaction (HPRR) has been recognized as an efficient approach to H₂O₂ sensing; however, the HPRR has always suffered from low tolerance against the oxygen reduction reaction (ORR), resulting in poor selectivity of the HPRR-based sensing platform. In this study, we find that the electrochemical HPRR occurs preferentially compared to the ORR when isolated Cu atoms anchored on carbon nitride (Cu₁/C₃N₄) are used as a single-atom electrocatalyst, which is theoretically attributed to the lower energy barrier of the HPRR than that of the ORR on a Cu₁/C₃N₄ single-atom catalyst (SAC). With the Cu₁/C₃N₄ SAC as the electrocatalyst, we fabricated microsensors that have a good response to H₂O₂, but not to O₂ or other electroactive neurochemicals. When implanted into a living rat brain, the microsensor shows excellent in vivo sensing performance, enabling its application in real-time quantitative investigation of the dynamics of H₂O₂ production induced by mercaptosuccinate and glutathione monoethyl ester in a living animal brain.

We have achieved the selective monitoring of H₂O₂ fluctuation in vivo free from O₂ interference by a single-atom Cu–N₂ electrocatalyst.

Electron-Rich Pincer Ligand-Coupled Cobalt Porphyrin Polymer with Single-Atom Sites for Efficient (Photo)Electrocatalytic CO2 Reduction at Ultralow Overpotential

Porphyrin and phthalocyanine complexes bearing single-atom catalytic sites (M-N₄ ) have been explored as promising electrocatalysts for CO₂ reduction reaction (CO₂ RR), whose activity can be improved by regulating the ligands and/or the metal centers. Moreover, their photosensitive features also provide the possibility for highly efficient photoelectrocatalytic CO₂ RR. Herein, a novel N'NN'-pincer-ligand (N₃ )-coupled cobalt porphyrin (CoPor-N₃ ) polymer is developed for realizing efficient (photo)electrocatalytic CO₂ RR. The unraveled electronic structure and (photo)electrocatalytic features suggest that a synergistic effect between the electron-rich N₃ ligands and the Co-N₄ single-atom sites in the CoPor-N₃ polymer results in the Co centers attaining more electrons, which is beneficial to facilitating the electron transfer to CO₂ for the activation and reduction processes. As expected, the resultant CoPor-N₃ polymer delivers a good long-term durability and high CO faradaic efficiency (96%) at an ultralow overpotential (0.39 V), which outperforms the CoPor alone and most porphyrin-/phthalocyanine-based electrocatalysts reported so far. Moreover, the photosensitivity of CoPor units can further reduce the overpotential to 0.34 V with a CO faradaic efficiency over 90% under light illumination. The present findings offer a new approach to constructing porphyrin-based photosensitive electrocatalysts with high-efficiency photoelectrocatalytic CO₂ RR.

Recent Advances in Interface Engineering for Electrocatalytic CO2 Reduction Reaction

Electrocatalytic CO₂ reduction reaction (CO₂RR) can store and transform the intermittent renewable energy in the form of chemical energy for industrial production of chemicals and fuels, which can dramatically reduce CO₂ emission and contribute to carbon-neutral cycle. Efficient electrocatalytic reduction of chemically inert CO₂ is challenging from thermodynamic and kinetic points of view. Therefore, low-cost, highly efficient, and readily available electrocatalysts have been the focus for promoting the conversion of CO₂. Very recently, interface engineering has been considered as a highly effective strategy to modulate the electrocatalytic performance through electronic and/or structural modulation, regulations of electron/proton/mass/intermediates, and the control of local reactant concentration, thereby achieving desirable reaction pathway, inhibiting competing hydrogen generation, breaking binding-energy scaling relations of intermediates, and promoting CO₂ mass transfer. In this review, we aim to provide a comprehensive overview of current developments in interface engineering for CO₂RR from both a theoretical and experimental standpoint, involving interfaces between metal and metal, metal and metal oxide, metal and nonmetal, metal oxide and metal oxide, organic molecules and inorganic materials, electrode and electrolyte, molecular catalysts and electrode, etc. Finally, the opportunities and challenges of interface engineering for CO₂RR are proposed.

Mechanistic and multiscale aspects of thermo-catalytic CO2 conversion to C1 products

The increasing environmental concerns due to anthropogenic CO2 emissions have called for an alternate sustainable source to fulfill rising chemical and energy demands and reduce environmental problems. The thermo-catalytic activation and conversion of abundantly available CO2, a thermodynamically stable and kinetically inert molecule, can significantly pave the way to sustainably produce chemicals and fuels and mitigate the additional CO2 load. This can be done through comprehensive knowledge and understanding of catalyst behavior, reaction kinetics, and reactor design. This review aims to catalog and summarize the advances in the experimental and theoretical approaches for CO2 activation and conversion to C1 products via heterogeneous catalytic routes. To this aim, we analyze the current literature works describing experimental analyses (e.g., catalyst characterization and kinetics measurement) as well as computational studies (e.g., microkinetic modeling and first-principles calculations). The catalytic reactions of CO2 activation and conversion reviewed in detail are: (i) reverse water-gas shift (RWGS), (ii) CO2 methanation, (iii) CO2 hydrogenation to methanol, and (iv) dry reforming of methane (DRM). This review is divided into six sections. The first section provides an overview of the energy and environmental problems of our society, in which promising strategies and possible pathways to utilize anthropogenic CO2 are highlighted. In the second section, the discussion follows with the description of materials and mechanisms of the available thermo-catalytic processes for CO2 utilization. In the third section, the process of catalyst deactivation by coking is presented, and possible solutions to the problem are recommended based on experimental and theoretical literature works. In the fourth section, kinetic models are reviewed. In the fifth section, reaction technologies associated with the conversion of CO2 are described, and, finally, in the sixth section, concluding remarks and future directions are provided.

ZIF/Co-C3N4 with enhanced electrocatalytic reduction of carbon dioxide activity by the photoactivation process

Introducing the effect of light into an electrocatalytic system is an effective method to improve electrocatalytic carbon dioxide reduction (CO₂RR). Here, the composite catalyst (ZIF/Co-C₃N₄) was prepared for the electrocatalytic reduction of carbon dioxide. The Faraday efficiency of the catalytic reduction of CO₂ to CO under light could reach 90.34% at -0.67 V vs. the RHE (reversible hydrogen electrode), which was 30% higher than that obtained under darkness, and the overpotential was reduced by 200 mV. Chemical kinetics experiments and in-situ transient photovoltage (TPV) tests show that the reason for highly efficient CO₂RR is intermediate CO₂^- formed by activated CO₂ in the electrocatalytic system under light. This work offers a deep insight into the photo-activated electrocatalytic reduction of carbon dioxide, and also opens a new way to devise efficient catalysts for CO₂RR.

Applications of medicinal chemistry for drug discovery against Acanthamoeba infections

Acanthamoeba is a genus of free-living amoebae, pervasively found in the environment. Most of its pathogenic species are the causative agent of sight-threatening Acanthamoeba keratitis and fatal granulomatous amoebic encephalitis. Despite the advancements in the field of chemotherapy, treating Acanthamoeba infections is still challenging due to incomplete knowledge of the complicated pathophysiology. In case of infection, the treatment regimen for the patients is often ineffective due to delayed diagnosis, poor specificity, and side-effects. Besides the resistance of Acanthamoeba cysts to most of the drugs, the recurrence of infection further complicates the recovery. Thus, it is necessary to develop an effective treatment which can eradicate these rare, but serious infections. Based on various computational and in vitro studies, it has been established that the synthetic scaffolds such as heterocyclic compounds may act as potential drug leads for the development of antiamoebic drugs. In this review, we report different classes of synthetic compounds especially heterocyclic compounds which have shown promising results against Acanthamoeba. Moreover, the antiamoebic activities of synthetic compounds with their possible mode of actions against Acanthamoeba, have been summarized and discussed in this review.

Polyoxometalate Interlayered Zinc-Metallophthalocyanine Molecular Layer Sandwich as Photocoupled Electrocatalytic CO2 Reduction Catalyst

Developing efficient and robust heterogeneous metallophthalocyanine electrocatalysts for CO₂ reduction remains a challenge. Here, a general synthetic method of zinc-metallophthalocyanine (MPc) molecular layer/polyoxometalate (POM) sandwich lamellar material is developed, and thus improved performance of electrocatalytic and photocoupled electrocatalytic CO₂ reduction is achieved. The incorporation of POM could prevent the packing of MPc molecular layers from aggregation, which would be favorable to the exposure of active sites. The molecular layer sandwich catalyst presents superior CO₂ reduction activity, delivering the highest CO Faradaic efficiency (FE_CO) of 96.1% at -0.7 V vs RHE in dark field. Under light irradiation, over 93% FE_CO is achieved in a broad potential range from -0.6 to -0.9 V vs RHE with a maximum of 96.2%, and the carbon monoxide turnover frequency could exceed 2060 h^-1. Photoelectrochemical tests and luminescence characterizations reveal the molecular layer is beneficial for carrier separation during light irradiation; density functional theory calculations and electron paramagnetic resonance indicated a 2-fold enhancement of the external light field on the catalytic performance.

Capturing Visible Light in Low-Band-Gap C4 N-Derived Responsive Bifunctional Air Electrodes for Solar Energy Conversion and Storage

We report facile synthesis of low-band-gap mesoporous C₄ N particles and their use as responsive bifunctional oxygen catalysts for visible-light-sensitive (VLS) rechargeable Zn-air battery (RZAB) and polymer-air battery (RPAB). Compared to widely studied g-C₃ N₄ , C₄ N shows a smaller band gap of 1.99 eV, with a larger photocurrent response, and it can function as visible-light-harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts, enabling effective photocoupling to tune oxygen catalysis. The C₄ N-enabled VLS-RZAB displays a low charge voltage of 1.35 V under visible light, which is below the theoretical RZAB voltage of 1.65 V, corresponding to a high energy efficiency of 97.78 %. Pairing a C₄ N cathode with a polymer anode also endows an VLS-RPAB with light-boosted charge performance. It is revealed that the ORR and OER active sites in C₄ N are separate carbon sites near pyrazine-nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.

Boosting CO2 Electroreduction via the Synergistic Effect of Tuning Cationic Clusters and Visible-Light Irradiation

Introducing an external light field can increase the intrinsic activity and energy efficiency for electrochemical CO₂ reduction. Herein, a synergistic strategy that introduces photosensitive components and visible light into a stable system is reported to improve the performance for CO₂ reduction. The catalytic kinetics studies indicate that the synergistic effect of implantation of cationic Ti and additional light driving is the primary responsibility for accelerating the first electron transfer to form a *COO^- intermediate. This leads to a satisfactory CO₂ -to-CO conversion for Zr/Ti-NB-Co in terms of high selectivity (Faradaic efficiency of 93.6% at -0.7 V), remarkable catalytic activity (production rate up to 546 mmol g^-1 h^-1 at -1.1 V), excellent long-term stability (without performance decay over 11 h), and large turnover frequency of 1028 h^-1 at -1.1 V under visible light. These results imply that the photodriven Ti-based porphyrin catalyst not only can deliver more electrons, but also can act as a photoswitch to adjust the electron transfer pathway.

Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective

Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy, which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO, formic acid, and hydrogen. By contrast, a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand, biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts, which significantly governs the reactivity and selectivity of CO2R. However, in biotic CO2R, operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.

Carbon support tuned electrocatalytic activity of a single-site metal-organic framework toward the oxygen reduction reaction

Metal-organic frameworks (MOFs) possess fantastic features such as structural diversity, tunable accessible pores and atomically dispersed active sites, holding tremendous potential as highly versatile platforms for fabricating single-site catalysts. The electrocatalytic activity of single-site MOFs can be improved and tuned via several approaches; however, the exploitation of different carbon supports to modulate the nature of single active sites in MOFs for electrocatalysis has not been reported. Here, we find that the electrocatalytic activity of single-site MOFs toward the oxygen reduction reaction (ORR) can be tuned by using carbon nanomaterials, i.e., carbon nanotubes and graphene, as supports through MOF-support interactions in the manner of geometric and electronic effects. The introduction of MOF-support interactions not only greatly improves the electrocatalytic performance of MOFs toward the ORR in terms of onset and half-wave potentials and current density, but also alters the reaction pathway of the ORR. This finding provides a new horizon for the design and synthesis of single-site MOFs for electrocatalysis.

Recent advances in single atom catalysts for the electrochemical carbon dioxide reduction reaction

The electrochemical carbon dioxide reduction reaction (CO2RR) offers a promising solution to mitigate carbon emission and at the same time generate valuable carbonaceous chemicals/fuels. Single atom catalysts (SACs) are encouraging to catalyze the electrochemical CO2RR due to the tunable electronic structure of the central metal atoms, which can regulate the adsorption energy of reactants and reaction intermediates. Moreover, SACs form a bridge between homogeneous and heterogeneous catalysts, providing an ideal platform to explore the reaction mechanism of electrochemical reactions. In this review, we first discuss the strategies for promoting the CO2RR performance, including suppression of the hydrogen evolution reaction (HER), generation of C1 products and formation of C2+ products. Then, we summarize the recent developments in regulating the structure of SACs toward the CO2RR based on the above aspects. Finally, several issues regarding the development of SACs for the CO2RR are raised and possible solutions are provided.

High-Efficiency Separation of n-Hexane by a Dynamic Metal-Organic Framework with Reduced Energy Consumption

The separation of n-alkanes from their branched isomers is vitally important to improve octane rating of gasoline. To facilitate mass transfer, adsorptive separation is usually operated under high temperatures in industry, which require considerable energy. Herein, we present a kind of dynamic pillar-layered MOF that exhibits self-adjustable structure and pore space, a behavior induced by guest molecules. A combination of the flexibility of the framework with the commensurate adsorption for n-hexane results in exceptional performance in separating hexane isomers. More significantly, lower temperature prompts the guest molecules to open the dynamic pores, which may provide a new perspective for optimized separation performance at lower temperatures with less energy consumption.

Towards self-doping multimetal porphyrin systems

An approach for the possible production of novel bimetallic self-doped porphyrin-based compounds of potential interest in material science is reported. Heating Cu(II)tetraphenylporphyrin (TPPCu) with chromocene at 120°C in benzonitrile affords the crystalline multimetal porphyrin system TPPCu/TPPCr in good yield. The X-ray single crystal structural analysis reveals a random distribution of TPPCu and TPPCr, with a Cu:Cr ratio of 71(2):29(2)%. Exploratory DFT calculations of TPPCu/TPPCr indicate little if any electron transfer. In contrast, calculations of a hypothetical cationic TPPCu/TPPRu system indicates the possibility of self-doping.