Tunable Catalysts Research Articles

DNA Catalysis: Design, Function, and Optimization

Catalytic DNA has gained significant attention in recent decades as a highly efficient and tunable catalyst, thanks to its flexible structures, exceptional specificity, and ease of optimization. Despite being composed of just four monomers, DNA’s complex conformational intricacies enable a wide range of nuanced functions, including scaffolding, electrocatalysis, enantioselectivity, and mechano-electro spin coupling. DNA catalysts, ranging from traditional DNAzymes to innovative DNAzyme hybrids, highlight the remarkable potential of DNA in catalysis. Recent advancements in spectroscopic techniques have deepened our mechanistic understanding of catalytic DNA, paving the way for rational structural optimization. This review will summarize the latest studies on the performance and optimization of traditional DNAzymes and provide an in-depth analysis of DNAzyme hybrid catalysts and their unique and promising properties.

Tailored Metal-Based Catalysts: A New Platform for Targeted Anticancer Therapies.

Innovative strategies for targeted anticancer therapies have gained significant momentum, with metal complexes emerging as tunable catalysts for more effective and safer treatments. Rational design and engineering of metal complexes enable the development of tailored molecular structures optimized for precision oncology. The strategic incorporation of metal complex catalysts within combinatorial therapies amplifies their anticancer properties. This perspective highlights the advancements in synthetic strategies and rational design since 2019, showing how tailored metal catalysts are optimized by designing structures to release or in situ synthesize active drugs, leveraging the target-specific characteristics to develop more precise cancer therapies. This review explores metal-based catalysts, including those conjugated with biomolecules, nanostructures, and metal-organic frameworks (MOFs), highlighting their catalytic activity in biological environments and their in vitro/in vivo performance. To sum up, the potential of metal complexes as catalysts to reshape the landscape of anticancer therapies and foster novel avenues for therapeutic advancement is emphasized.

Restructuring dynamics of surface species in bimetallic nanoparticles probed by modulation excitation spectroscopy

Restructuring of metal components on bimetallic nanoparticle surfaces in response to the changes in reactive environment is a ubiquitous phenomenon whose potential for the design of tunable catalysts is underexplored. The main challenge is the lack of knowledge of the structure, composition, and evolution of species on the nanoparticle surfaces during reaction. We apply a modulation excitation approach to the X-ray absorption spectroscopy of the 30 atomic % Pd in Au supported nanocatalysts via the gas (H2 and O2) concentration modulation. For interpreting restructuring kinetics, we correlate the phase-sensitive detection with the time-domain analysis aided by a denoising algorithm. Here we show that the surface and near-surface species such as Pd oxides and atomically dispersed Pd restructured periodically, featuring different time delays. We propose a model that Pd oxide formation is preceded by the build-up of Pd regions caused by oxygen-driven segregation of Pd atoms towards the surface. During the H2 pulse, rapid reduction and dissolution of Pd follows an induction period which we attribute to H2 dissociation. Periodic perturbations of nanocatalysts by gases can, therefore, enable variations in the stoichiometry of the surface and near-surface oxides and dynamically tune the degree of oxidation/reduction of metals at/near the catalyst surface.

A Theoretical Benchmark of the Geometric and Optical Properties for 3d Transition Metal Nanoclusters via Density Functional Theory.

Understanding structure-property relationships in atomically precise metal nanoclusters is vital in finding selective and tunable catalysts. In this study, density functional theory (DFT) was used to benchmark seven exchange correlation functionals at different basis sets for 17 atomically precise nanoclusters against experimentally determined geometries, band gaps, and optical gaps. The set contains both monometallic and bimetallic clusters that possess at least two types of 3d transition metals (specifically, Cu, Ni, Fe, or Co). The benchmark highlights that PBE0 is a good functional to use regardless of the basis set, and Minnesota functionals do well with respect to specific metals. Further, while long-range corrected functionals overestimate band and optical gaps, they model absorption features better than the other considered functionals. The study additionally looks at the photoinduced hydrogen evolution reaction (HER) and the CO2 reduction mechanism on nanoclusters reported from the literature.

Photothermally Triggered Nanoreactors with a Tunable Catalyst Location and Catalytic Activity.

Thermosensitive microgels based on poly(N-isopropylacrylamide) (PNIPAm) have been widely used to create nanoreactors with controlled catalytic activity through the immobilization of metal nanoparticles (NPs). However, traditional approaches with metal NPs located only in the polymer network rely on electric heating to initiate the reaction. In this study, we developed a photothermal-responsive yolk-shell nanoreactor with a tunable location of metal NPs. The catalytic performance of these nanoreactors can be controlled by both light irradiation and conventional heating, that is, electric heating. Interestingly, the location of the catalysts had a significant impact on the reduction kinetics of the nanoreactors; catalysts in the shell exhibited higher catalytic activity compared with those in the core, under conventional heating. When subjected to light irradiation, nanoreactors with catalysts loaded in the core demonstrated improved catalytic performance compared to direct heating, while nanoreactors with catalysts in the shell exhibited relatively similar activity. We attribute this enhancement in catalytic activity to the spatial distribution of the catalysts and the localized heating within the polydopamine cores of the nanoreactors. This research presents exciting prospects for the design of innovative smart nanoreactors and efficient photothermal-assisted catalysis.

Dual Atom Catalysts for Energy and Environmental Applications.

The pursuit of high metal utilization in heterogeneous catalysis has triggered the burgeoning interest of various atomically dispersed catalysts. Our aim in this review is to assess key recent findings in the synthesis, characterization, structure-property relationship and computational studies of dual-atom catalysts (DACs), which cover the full spectrum of applications in thermocatalysis, electrocatalysis and photocatalysis. In particular, combination of qualitative and quantitative characterization with cooperation with DFT insights, synergies and superiorities of DACs compare to counterparts, high-throughput catalyst exploration and screening with machine-learning algorithms are highlighted. Undoubtably, it would be wise to expect more fascinating developments in the field of DACs as tunable catalysts.

Dual Atom Catalysts for Energy and Environmental Applications

AbstractThe pursuit of high metal utilization in heterogeneous catalysis has triggered the burgeoning interest of various atomically dispersed catalysts. Our aim in this review is to assess key recent findings in the synthesis, characterization, structure‐property relationship and computational studies of dual‐atom catalysts (DACs), which cover the full spectrum of applications in thermocatalysis, electrocatalysis and photocatalysis. In particular, combination of qualitative and quantitative characterization with cooperation with DFT insights, synergies and superiorities of DACs compare to counterparts, high‐throughput catalyst exploration and screening with machine‐learning algorithms are highlighted. Undoubtably, it would be wise to expect more fascinating developments in the field of DACs as tunable catalysts.

Operando Electrochemical Liquid-Cell Scanning Transmission Electron Microscopy (EC-STEM) Studies of Evolving Cu Nanocatalysts for CO2 Electroreduction

The design and synthesis of nanocatalysts with well-defined sizes, compositions, and structures have revolutionized our accessibility to tunable catalyst activity and selectivity for a variety of energy-related electrochemical reactions. Nonetheless, establishing structure-(re)activity correlations requires the understanding of the dynamic evolution of pristine nanocatalysts and the identification of their active states under operating conditions. We previously communicated the operando observation of Cu nanocatalysts evolving into active metallic Cu nanograins for CO2 electroreduction (Yang et al. Nature 2023, 614, 262−269). Here, we expand our discussion to the technical capabilities and further research applications of operando electrochemical liquid-cell scanning transmission electron microscopy (EC-STEM), which enables quantitative electrochemistry while tracking dynamic structural evolution of sub-10 nm Cu nanocatalysts. The coexistent H2 bubbles, often disruptive to operando spectroscopy, are an effective approach to create a thin-liquid layer that significantly improves spatial resolution while remaining electrochemically accessible to Cu nanocatalysts. Operando four-dimensional (4D) STEM in liquids provides insights into the complex structure of active polycrystalline metallic Cu nanograins. With continuous technical developments, we anticipate that operando EC-STEM will evolve into a powerful electroanalytical method to advance our understanding of a variety of nanoscale electrocatalysts at solid/liquid interfaces.

Electroreduction of Carbon Dioxide to Acetate using Heterogenized Hydrophilic Manganese Porphyrins.

The electrochemical reduction of carbon dioxide (CO2 ) to value-added chemicals is a promising strategy to mitigate climate change. Metalloporphyrins have been used as a promising class of stable and tunable catalysts for the electrochemical reduction reaction of CO2 (CO2 RR) but have been primarily restricted to single-carbon reduction products. Here, we utilize functionalized earth-abundant manganese tetraphenylporphyrin-based (Mn-TPP) molecular electrocatalysts that have been immobilized via electrografting onto a glassy carbon electrode (GCE) to convert CO2 with overall 94 % Faradaic efficiencies, with 62 % being converted to acetate. Tuning of Mn-TPP with electron-withdrawing sulfonate groups (Mn-TPPS) introduced mechanistic changes arising from the electrostatic interaction between the sulfonate groups and water molecules, resulting in better surface coverage, which facilitated higher conversion rates than the non-functionalized Mn-TPP. For Mn-TPP only carbon monoxide and formate were detected as CO2 reduction products. Density-functional theory (DFT) calculations confirm that the additional sulfonate groups could alter the C-C coupling pathway from *CO→*COH→*COH-CO to *CO→*CO-CO→*COH-CO, reducing the free energy barrier of C-C coupling in the case of Mn-TPPS. This opens a new approach to designing metalloporphyrin catalysts for two carbon products in CO2 RR.

Understanding the important variables to optimize glycolysis of polyethylene terephthalate with lanthanide-containing ionic liquids

Lanthanide metal ionic liquids (MILs) are tunable catalysts for the glycolysis of poly(ethylene terephthalate). Enhanced cooperativity with high ionic liquid : metal salt ratios lowers the required metal content to increase catalyst sustainability.

On the 3D printed catalyst for biomass-bio-oil conversion: Key technologies and challenges

The devastative effects of traditional fossil fuel consumption have made biomass (e.g., plants, wood, and waste) a widely used renewable source of energy. The variety in biomass properties makes tunable catalysts an essential ingredient to promote reactions for desired molecule outputs. Catalysts with optimal catalytic performance are typically structured with complicated morphology, such as high porosity and sophistic pore network, which makes it challenging for catalyst fabrication. Recent progress in utilizing 3D printing as the fabrication method has demonstrated great potential of handling the complex structure while improving catalytic performance; however, rare work has focused on biomass-bio-oil conversion (BBC). With the aim of developing the optimal structured catalysts for BBC applications, this paper particularly reviewed 1) typical catalysts used for biomass conversion applications, 2) 3D printed catalysts, and 3) design and optimization of structured catalysts. It is found that the BBC is often isolated from manufacturing and focused more on different catalyst composition with transition metals to provide the desired catalyst architecture and further to improve upgrading of the BBC product. Current work on 3D-printed catalysts also show deficiency in several aspects including formation of coke and catalyst deactivation, lack of a comprehensive design for the catalyst structure (e.g., mostly 2D structures), absence of manufacturing constraints in design operation, and insufficient resolution of 3D printing methods. To solve these issues, several potential research directions and opportunities are discussed at the end of the study.

Tuning the electrocatalytic CO reduction on bilayer C3N via rotation, translation and metal intercalation

Owing to the crucial role of the CO reduction in the sustainable development and carbon neutrality, designing tunable electrocatalyst with high efficiency is the top priority for the controllable CO reduction reaction (CORR). Inspired by the interlayer van der Waals coupling modification, we have theoretically explored the tunable catalyst for the CO electrochemical reduction based on the bilayer C3N (b-C3N) via the rotation, translation and transition metal intercalation. Through careful computational screening, we found that rotational and/or translational intermodulation to the transitional metal intercalated b-C3N (TM/b-C3N) can tune its catalytic activity and selectivity efficiently and therefore control the reaction rates and final product distribution. The electronic analysis revealed the half-metallic characteristic of the TM intercalated b-C3N and found that the electrons transferring from the intercalated metal to the adsorbed molecules with the rotated (or translated) b-C3N acting as transferring bridge can further activate the catalyst surface. This study provides a new strategy to design novel CORR catalyst with tunable catalytic activities by mechanical operations, such as rotation, translation and intercalation, and will open a new door for the application of controllable COx reduction.

Tug‐of‐War between Two Distinct Catalytic Sites Enables Fast and Selective Ring‐Opening Copolymerizations

AbstractRing‐opening copolymerizations have emerged as a powerful approach towards the creation of sustainable polymers. Typical H‐bonding catalysts for ring‐opening are subject to a single catalytic site. Here we describe a H‐bond‐donor/Lewis‐acidic‐boron organocatalyst featuring two distinct catalytic sites in one molecule. The ring‐opening copolymerization of epoxides with anhydride mediated by these modular, and tunable catalysts achieves high selectivity (>99 % polyester selectivity) and markedly higher activity compared to either of the di‐thiourea analogues or any combinations of them. Calculations and experimental studies reveal that the superior catalytic performance arises from tug‐of‐war between two differentiated catalytic sites: thiourea pulls off the propagating chain‐end from boron center, simultaneously enhancing the role of monomer activation and also nucleophilicity of the propagation intermediates.

Tug‐of‐War between Two Distinct Catalytic Sites Enables Fast and Selective Ring‐Opening Copolymerizations

AbstractRing‐opening copolymerizations have emerged as a powerful approach towards the creation of sustainable polymers. Typical H‐bonding catalysts for ring‐opening are subject to a single catalytic site. Here we describe a H‐bond‐donor/Lewis‐acidic‐boron organocatalyst featuring two distinct catalytic sites in one molecule. The ring‐opening copolymerization of epoxides with anhydride mediated by these modular, and tunable catalysts achieves high selectivity (>99 % polyester selectivity) and markedly higher activity compared to either of the di‐thiourea analogues or any combinations of them. Calculations and experimental studies reveal that the superior catalytic performance arises from tug‐of‐war between two differentiated catalytic sites: thiourea pulls off the propagating chain‐end from boron center, simultaneously enhancing the role of monomer activation and also nucleophilicity of the propagation intermediates.

A Hydrometalation Initiation Mechanism via a Discrete Cobalt-Hydride for a Rapid and Controlled Radical Polymerization.

Cobalt-mediated radical polymerization (CMRP) is a versatile technique for controlling the polymerization of vinyl monomers via reversible termination using CoII complexes as persistent radical deactivators. Here, we report a facile approach for the in situ generation of Co-H as a discrete initiator and mediator for CMRP of acrylate and acrylamide monomers, overcoming the limitations of existing initiation strategies. In situ oxidation of a CoII complex followed by transmetalation with silane generates a Co-H species, which initiates polymerization via hydrometalation of the monomer. This method precludes an induction period with excellent control over targeted molecular weight and dispersity. Strikingly, our approach allows complete polymerization when the induction period ends for conventional CMRP. A broad scope of monomers is amenable to this protocol, including acrylates and acrylamides. Tunable catalyst electronics afford tailored dispersity while maintaining agreement in molecular weight in stark contrast to conventional methods. Elimination of this induction period imbues polymerization behavior entirely to the catalyst electronic effects on reversible deactivation/activation rates.

Sterically Demanding Flexible Phosphoric Acids for Constructing Efficient and Multi-Purpose Asymmetric Organocatalysts.

Herein, we present a novel approach for various asymmetric transformations of cyclic enones. The combination of readily accessible chiral diamines and sterically demanding flexible phosphoric acids resulted in a simple and highly tunable catalyst framework. The careful optimization of the catalyst components led to the identification of a particularly powerful and multi‐purpose organocatalyst, which was successfully applied for asymmetric epoxidations, aziridinations, aza‐Michael‐initiated cyclizations, as well as for a novel Robinson‐like Michael‐initiated ring closure/aldol cyclization. High catalytic activities and excellent stereocontrol was observed for all four reaction types, indicating the excellent versatility of our catalytic system. Furthermore, a simple change in the diamine's configuration provided easy access to both product antipodes in all cases.

Sterically Demanding Flexible Phosphoric Acids for Constructing Efficient and Multi-Purpose Asymmetric Organocatalysts.

Herein, we present a novel approach for various asymmetric transformations of cyclic enones. The combination of readily accessible chiral diamines and sterically demanding flexible phosphoric acids resulted in a simple and highly tunable catalyst framework. The careful optimization of the catalyst components led to the identification of a particularly powerful and multi-purpose organocatalyst, which was successfully applied for asymmetric epoxidations, aziridinations, aza-Michael-initiated cyclizations, as well as for a novel Robinson-like Michael-initiated ring closure/aldol cyclization. High catalytic activities and excellent stereocontrol was observed for all four reaction types, indicating the excellent versatility of our catalytic system. Furthermore, a simple change in the diamine's configuration provided easy access to both product antipodes in all cases.

Hierarchical Fe Doped Co Oxide/Hydroxide Nanosheet Arrays as Highly Efficient Oxygen Evolution Catalysts Prepared by Hydrothermal Etching of FeCo Prussian Blue Analogue

AbstractEarth‐abundant metal oxides/hydroxides have recently been identified as promising catalysts for oxygen evolution reaction (OER) in alkaline media, while the overall efficiency is still limited by the sluggish kinetics. Therefore, searching for facile and effective method to prepare composition and morphology tunable catalyst, as well as understanding its reactivity are urgent tasks. Here, we report a hydrothermal etching strategy for the synthesis of Fe doped Co oxides/hydroxide hybrid catalyst with hierarchical nanosheet array architecture. The as‐obtained catalyst shows an overpotential of 219 mV without iR compensation at 10 mA/cm2 and a low Tafel slope of 46.4 mV/dec, surpassing the other control catalysts in this work and most similar catalysts in literature. Comprehensive studies confirm that both composition and morphology can be rationally tuned by adjusting the hydrothermal etching parameters, and the improvement of activity is attributed to the highly active Fe doped Co oxides/hydroxide species together with the unique 3D hierarchical structure.

Calcined polycyclotriphosphazene@NiAl-LDH@RhxNi1-x: A novel hierarchically oriented composition tunable catalyst for green and sustainable hydrogen generation

The ever decreasing amount of fossil fuels and increasing environmental pollution are alarming threats for green and sustainable future. Designing a new catalyst is, therefore, of paramount significance in the quest to discover sustainable, robust, and environmentally benign materials for clean and sustainable energy generation. Herein, we developed a hierarchically oriented catalyst of calcined poly(ferrocenedimethano)-cyclotriphosphazene-microspheres (CPFC-MS) supported with nickel-aluminum layered double hydroxide and decorated with nanoparticles (NPs) of rhodium-nickel, NiAl-LDH@RhxNi1-x (x = 2.06–6.75), for H2 generation from ammonia borane (AB) hydrolysis. The highly active catalyst was characterized by scanning electron microscopy (SEM), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) and TEM, energy dispersive X-ray spectroscopy (EDX), fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The as-fabricated CPFC-MS@NiAl-LDH@RhxNi1-x (x = 2.06–6.75) catalysts were tested for AB hydrolysis and the results showed remarkable performance and higher stability for H2 generation. The CPFC-MS@NiAl-LDH@Rh2.06Ni7.32 catalyst, having the lowest Rh-contents, exhibited maximum H2 generation with a turn over frequency (TOF) of 780 mol H2 hr−1 mol Rh−1 and an activation energy (Ea) of 40.3 kJ/mol with excellent sustainability. The superior activity is ascribed to the synergetic effect between RhNi NPs and their well-dispersion over hierarchically oriented CPFC-MS@NiAl-LDH support, while higher stability due to LDH-AlNi/RhNi attractions. This work will provide new opportunities for polyphosphazenes and LDH derived hierarchically oriented sustainable catalysts for green energy production for sustainable future.

High Performance Tunable Catalysts Prepared by Using 3D Printing.

Honeycomb monoliths are the preferred supports in many industrial heterogeneous catalysis reactions, but current extrusion synthesis only allows obtaining parallel channels. Here, we demonstrate that 3D printing opens new design possibilities that outperform conventional catalysts. High performance carbon integral monoliths have been prepared with a complex network of interconnected channels and have been tested for carbon dioxide hydrogenation to methane after loading a Ni/CeO2 active phase. CO2 methanation rate is enhanced by 25% at 300 °C because the novel design forces turbulent flow into the channels network. The methodology and monoliths developed can be applied to other heterogeneous catalysis reactions, and open new synthesis options based on 3D printing to manufacture tailored heterogeneous catalysts.