Super Catalyst Research Articles

Multifunction magnetic chiral MOF composite: A novel post-synthetic super catalyst for enhancing the asymmetric CO2 fixation

Here in, a novel neutral Chiral Metal−Organic Framework (CMOF) composite, Cu(II)-l-proline/TCT/APTES/Fe3O4/MIL-101(Fe) (Cu(II)-HPro/TCT/APTES/Fe3O4/MIL-101(Fe)), has been derived from the chiral Cu(II)-l-proline complex (Cu(II)-HPro) attached to TCT/APTES/Fe3O4 and MIL-101(Fe). Achiral MIL-101(Fe) was chiralized by the incorporation of chiral Cu(II)-HPro complex anchored to TCT/APTES/Fe3O4 using ultrasonic-assisted electrostatic self-assembly technique (postsynthetic modification). The resulted super catalyst has chiral species acting as Lewis base sites, together with two active metal sites (Fe and Cu) acting as Lewis acid centers leading to multifunctionality. Due to chiral auxiliary Lewis bases and Lewis acids, the catalytic activity of the Cu(II)-HPro/TCT/APTES/Fe3O4/MIL-101(Fe) composite was evaluated in asymmetric catalysis of prochiral substrates. This asymmetric super catalyst has proved to be highly active in CO2 fixation reaction at ambient pressure, low-temperature, solvent-free medium with high conversion and enantioselectivity. Based on the results, enantiomeric excess (ee) [97 % (S)], carbonate selectivity (>99 %), and conversion (>99 %) all demonstrate the superior performance of the investigated catalytic system. Furthermore, the magnetic characteristic, together with excellent structure stability, leads to high recyclability for 7 runs without a significant reduction of catalytic activity. The outcomes showed that chiralization of MIL-101(Fe) could occur through a simple and green approach, which may be a practical way to create chiral multifunctionalized metal−organic frameworks (MOFs).

Pt nanoparticles anchored on Ti3C2 MXene‐derived TiO2 nanosheets for enhanced hydrogen evolution reaction

AbstractPlatinum (Pt)‐based electrocatalysts are the most excellent catalysts for hydrogen evolution reaction (HER). But Pt is limited and expensive on earth, adding the proper matrix to disperse and anchor Pt is a viable way to reduce Pt consumption. Based on the excellent structure and electrochemical properties of two‐dimensional (2D) MXene, the Ti3C2 MXene‐derived TiO2 supported Pt nanoparticles (NPs) catalysts should have good catalytic performance in theoretically, but it has not been studied in experimentally. In this study, Pt NPs were anchored on the multilayer Ti3C2 MXene‐derived TiO2 nanosheets (NSs) to obtain super catalyst. The as‐prepared Pt/TiO2/Ti3C2 catalyst exhibited excellent HER performance under acidic conditions, with an overpotential of 147 mV and a small Tafel slope (54 mv dec−1) at 10 mA cm−2. Meanwhile, it has good stability under acidic conditions, and the activity has no obvious attenuation after 1000 CV cycles. In addition, the results show that anchoring Pt NPs on Ti3C2 MXene‐derived TiO2 NSs can help to reduce the binding energy and hybridization strength between H atoms and the support, thereby promoting the fast hydrogen adsorption‐desorption kinetics and enhancing the activity of HER. This work provides a new avenue for rational construction of high‐performance Ti3C2‐based catalysts.

Low temperature mechano-catalytic biofuel conversion using liquid metals

Liquid metals are super catalysts that facilitate reactions at low temperatures while also providing new reaction pathways by the incorporation of co-catalysts. Synthesising H2 and C2H4 from renewable resources, with a low carbon footprint, is crucial for environmental sustainability. However, the high temperature requirement and over-reliance on fossil fuels restrict the sustainable production of H2 and C2H4. Here we demonstrate a hybrid catalytic system, which realises the conversion of renewable biofuels into mostly H2 and C2H4 at near room temperature, by employing mechanical energy as the stimulus and liquid metal gallium (Ga) together with nickel (Ni) particles as co-catalysts. During the collision of the suspended nano/micro-sized Ga/Ni co-catalysts, the biofuels, including canola oil and other liquid hydrocarbons, are converted at the interfaces of the catalytic materials. Density functional theory calculations show that CH and CC bond dissociation reactions on the Ga surface proceed under low energy conditions. These biofuels are converted into mainly H2 and C2H4 with CH4, CO, CO2, C2H2, C3H6 and solid carbon as other by-products. With mild heating at ∼ 60 °C and the use of a 20 ml reactor, the process is capable of producing 2.15 cm3 of H2 and 2.47 cm3 of C2H4 per hour with canola oil as the feedstock. Meanwhile, the durability and potential practical applicability of the system are demonstrated with 10 days of continuous operation. This approach offers an alternative for H2 and C2H4 production without involving high reaction temperatures and fossil fuel hydrocarbons.

Offsite Sustainability—Disentangling the Rhetoric through Informed Mindset Change

The construction sector and concomitant supply chain has been acknowledged in the literature as a major contributor to environmental “stress”, from the design, sourcing and extraction of raw materials through to transportation, design, construction and demolition. Clear indicators/solutions have been showcased as vehicles for reducing this stress, ranging from lifecycle costing through to waste reduction strategies, carbon assessment and “green” environmental assessment tools to name but a few. However, this paper argues that whilst some of these (intervention strategies) may have had some positive effects, the main challenge rests with people—inter alia, the key decision-makers and leadership structures with the “position power” to effect change. Acknowledging this as a supposition, this paper uses three discreet construction organisations engaging in offsite construction as a micro-study (cf. cross-case study) to evaluate sustainability perceptions. In doing so, it focuses specifically on sustainability practices and business processes underpinning technology (adoption, absorption and diffusion), including the perceptions of different stakeholders involved in each of these three companies. In total, 30 respondents from three organisations (cases) participated in this study, representing three tiers of management (top, middle and first line). Priority areas are highlighted, along with the reasons supporting these perspectives. Findings from this work present a new technology diffusion sustainability model for offsite construction. This model identifies sustainability causal links, super catalysts, actuators, barriers, forces and facilitators. More importantly perhaps, this work presents a clear case for “conjoined thinking” in order to instill a collective mindset change and common purpose for those wishing to evidence offsite sustainability.

Chitosan@Carboxymethylcellulose/CuO-Co2O3 Nanoadsorbent as a Super Catalyst for the Removal of Water Pollutants.

In this work, an efficient nanocatalyst was developed based on nanoadsorbent beads. Herein, carboxymethyl cellulose–copper oxide-cobalt oxide nanocomposite beads (CMC/CuO-Co2O3) crosslinked by using AlCl3 were successfully prepared. The beads were then coated with chitosan (Cs), Cs@CMC/CuO-Co2O3. The prepared beads, CMC/CuO-Co2O3 and Cs@CMC/CuO-Co2O3, were utilized as adsorbents for heavy metal ions (Ni, Fe, Ag and Zn). By using CMC/CuO-Co2O3 and Cs@CMC/CuO-Co2O3, the distribution coefficients (Kd) for Ni, Fe, Ag and Zn were (41.166 and 6173.6 mLg−1), (136.3 and 1500 mLg−1), (20,739.1 and 1941.1 mLg−1) and (86.9 and 2333.3 mLg−1), respectively. Thus, Ni was highly adsorbed by Cs@CMC/CuO-Co2O3 beads. The metal ion adsorbed on the beads were converted into nanoparticles by treating with reducing agent (NaBH4) and named Ni/Cs@CMC/CuO-Co2O3. Further, the prepared nanoparticles-decorated beads (Ni/Cs@CMC/CuO-Co2O3) were utilized as nanocatalysts for the reduction of organic and inorganic pollutants (4-nitophenol, MO, EY dyes and potassium ferricyanide K3[Fe(CN)6]) in the presence of NaBH4. Among all catalysts, Ni/Cs@CMC/CuO-Co2O3 had the highest catalytic activity toward MO, EY and K3[Fe(CN)6], removing up to 98% in 2.0 min, 90 % in 6.0 min and 91% in 6.0 min, respectively. The reduction rate constants of MO, EY, 4-NP and K3[Fe(CN)6] were 1.06 × 10−1, 4.58 × 10−3, 4.26 × 10−3 and 5.1 × 10−3 s−1, respectively. Additionally, the catalytic activity of the Ni/Cs@CMC/CuO-Co2O3 beads was effectively optimized. The stability and recyclability of the beads were tested up to five times for the catalytic reduction of MO, EY and K3[Fe(CN)6]. It was confirmed that the designed nanocomposite beads are ecofriendly and efficient with high strength and stability as catalysts for the reduction of organic and inorganic pollutants.

Front Cover: Chemically Modified Lipase from Thermomyces lanuginosus with Enhanced Esterification and Transesterification Activities (ChemCatChem 21/2021)

The Front Cover shows a super catalyst (SC) lipase obtained through chemical modification for the production of several industrial products like ester-based compounds. In their Full Paper, J. Noro et al. studied the impact of the chemical modification of lipase from Thermomyces lanuginosus with dodecyl aldehyde, on its esterification and transesterification activity. The enzyme, modified with four dodecyl chains, showed an outstanding improvement of the catalytic performance for both reactions, comparing to the unmodified lipase. The most notorious results were achieved when longer chain-length alcohols were used for the transesterification of p-nitrophenyl palmitate and for the esterification of oleic acid. The novel enzyme modification strategy developed by the authors, resulted in the transformation of a super catalyst, with countless fields of applications, including the production of ester-based products for cosmetic and medical fields. More information can be found in the Full Paper by J. Noro et al.

Chemically Modified Lipase from Thermomyces lanuginosus with Enhanced Esterification and Transesterification Activities

AbstractLipase from Thermomyces lanuginosus is one of the most explored enzymes for the esterification of several added‐value industrial compounds, such as biodiesel, fragrances, and flavors. Its selectivity in these reactions is mostly related with its activity towards small alcohols. In this work, the impact of the chemical modification, with 4 dodecyl chains at its surface, was evaluated regarding its transesterification and esterification activities, comparing with the native form. Linear size‐differentiated alcohols (from 1 to 20 carbons in the aliphatic chain) were used to explore for the first time the effect of the chain length in both transesterification and esterification reactions, using p‐nitrophenyl palmitate and oleic acid as model compounds, respectively. The chemically modified lipase showed an outstanding improvement of its catalytic performance than the native enzyme, being this increase directly proportional to the size of the alcohols chain used as substrates. The enormous potential and remarkable versatility of this novel super catalyst was here demonstrated, where diverse types of esters, differing in their potential applications (biodiesel, cosmetics, fine chemistry), were efficiently synthesized. The produced esters were fully characterized by 1H NMR, GC‐MS, and FTIR.

Standardized Procedures Important for Improving Low-Temperature Ceramic Fuel Cell Technology: From Transient to Steady State Assessment.

As the stress–strain curve of standardized metal samples provides the basic details about mechanical properties of structural materials, the polarization curve or current–voltage characteristics of fuel cells are vitally important to explore the scientific mechanism of various solid oxide cells aiming at low operational temperatures (below 600 °C), ranging from protonic conductor ceramic cells (PCFC) to emerging Semiconductor ionic fuel cell (SIFC)/Semiconductor membrane fuel cells (SMFC). Thus far, worldwide efforts to achieve higher nominal peak power density (PPD) at a low operational temperature of over 0.1 s/cm ionic conductivity of electrolyte and super catalyst electrode is the key challenge for SIFCs. Thus, we illustrate an alternative approach to the present PPD concept and current–voltage characteristic. Case studies reveal that the holy grail of 1 W/cm2 from journal publications is expected to be reconsidered and normalized, since partial cells may still remain in a transient state (TS) to some extent, which means that they are unable to fulfill the prerequisite of a steady state (SS) characteristic of polarization curve measurement. Depending on the testing parameters, the reported PPD value can arbitrarily exist between higher transient power density (TPD) and lower stable power density (SPD). Herein, a standardized procedure has been proposed by modifying a quasi-steady state (QSS) characterization based on stabilized cell and time-prolonged measurements of common I–V plots. The present study indicates, when compared with steady state value, that QSS power density itself still provides a better approximation for the real performance of fuel cells, and concurrently recalls a novel paradigm transformation from a transient to steady state perspective in the oxide solid fuel cell community.

Boosting NAD+ with a small molecule that activates NAMPT

Pharmacological strategies that boost intracellular NAD+ are highly coveted for their therapeutic potential. One approach is activation of nicotinamide phosphoribosyltransferase (NAMPT) to increase production of nicotinamide mononucleotide (NMN), the predominant NAD+ precursor in mammalian cells. A high-throughput screen for NAMPT activators and hit-to-lead campaign yielded SBI-797812, a compound that is structurally similar to active-site directed NAMPT inhibitors and blocks binding of these inhibitors to NAMPT. SBI-797812 shifts the NAMPT reaction equilibrium towards NMN formation, increases NAMPT affinity for ATP, stabilizes phosphorylated NAMPT at His247, promotes consumption of the pyrophosphate by-product, and blunts feedback inhibition by NAD+. These effects of SBI-797812 turn NAMPT into a “super catalyst” that more efficiently generates NMN. Treatment of cultured cells with SBI-797812 increases intracellular NMN and NAD+. Dosing of mice with SBI-797812 elevates liver NAD+. Small molecule NAMPT activators such as SBI-797812 are a pioneering approach to raise intracellular NAD+ and realize its associated salutary effects.

Mesoporous carbon nanoparticles: a super catalyst support for fuel cells

Ionic liquid-modified mesoporous carbon nanoparticles exhibit good electrochemical activity compared with commercial Pt/C catalyst and Pt nanoparticles.

An approach for catalyst design in artificial photosynthetic systems: focus on nanosized inorganic cores within proteins

Some enzymes can be considered as a catalyst having a nanosized inorganic core in a protein matrix. In some cases, the metal oxide or sulfide clusters, which can be considered as cofactors in enzymes, may be recruited for use in other related reactions in artificial photosynthetic systems. In other words, one approach to design efficient and environmentally friendly catalysts in artificial photosynthetic systems for the purpose of utilizing sunlight to generate high energy intermediates or useful material is to select and utilize inorganic cores of enzymes. For example, one of the most important goals in developing artificial photosynthesis is hydrogen production. However, first, it is necessary to find a "super catalyst" for water oxidation, which is the most challenging half reaction of water splitting. There is an efficient system for water oxidation in cyanobacteria, algae, and plants. Published data on the Mn-Ca cluster have provided details on the mechanism and structure of the water oxidizing complex as a Mn-Ca nanosized inorganic core in photosystem II. Progress has been made in introducing Mn-Ca oxides as efficient catalysts for water oxidation in artificial photosynthetic systems. Here, in the interest of designing efficient catalysts for other important reactions in artificial photosynthesis, a few examples of our knowledge of inorganic cores of proteins, and how Nature used them for important reactions, are discussed.

Biological water oxidation: Lessons from Nature

Hydrogen production by water splitting may be an appealing solution for future energy needs. To evolve hydrogen efficiently in a sustainable manner, it is necessary first to synthesize what we may call a ‘super catalyst’ for water oxidation, which is the more challenging half reaction of water splitting. An efficient system for water oxidation exists in the water oxidizing complex in cyanobacteria, algae and plants; further, recently published data on the Manganese–calcium cluster have provided details on the mechanism and structure of the water oxidizing complex. Here, we have briefly reviewed the characteristics of the natural system from the standpoint of what we could learn from it to produce an efficient artificial system. In short, to design an efficient water oxidizing complex for artificial photosynthesis, we must learn and use wisely the knowledge about water oxidation and the water oxidizing complex in the natural system. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

ChemInform Abstract: Design of Super Catalysts for Asymmetric Hydrogenations and Their Utilization in Practical Asymmetric Syntheses

Recently, we have proposed a new designing concept, “Respective Control Concept”, for developing highly efficient chiral bisphosphine ligands. On the basis of our concept, new chiral bisphosphine ligands, BCPM, MOD-BPPM, MOD-DIOP, etc. have been synthesized. Their rhodium complexes have been found to show very high catalytic activity and enantioselectivity in the asymmetric hydrogenations of prochiral carbonyl and olefinic compounds. Practical asymmetric syntheses of useful biologically active compounds have been realized by using these hydrogenations as key reactions.