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Highly efficient electrochemical nitrate reduction could become a key process for sustainable ammonia production overcoming many limitations of the Haber–Bosch process. Current state-of-the-art electrocatalysts have severe drawbacks regarding yield, selectivity and energy efficiency when dealing with dilute nitrate solutions. Herein, we report a layered double hydroxide (LDH)/Cu foam hybrid electrocatalyst that offers a potential solution to this challenge. The [Ni0.75Fe0.25(OH)2](CO3)0.125 (Ni3Fe–CO3 LDH) exhibits an appropriate kinetic energy barrier for the Volmer step generating hydrogen radicals as well as suppressing H–H bond formation by inhibition of the Heyrovsky step. The electrochemically generated hydrogen radicals transfer to a Cu surface enabling NO3− reduction to NH3. The Ni3Fe–CO3 LDH/Cu foam hybrid electrode exhibits an 8.5-fold higher NH3 yield compared to a pristine Cu surface, while exhibiting an NH3 selectivity of 95.8% at 98.5% NO3− conversion. The best half-cell energy efficiency (36.6%) was recorded while achieving 96.8% faradaic efficiency at −0.2 V in 5 mM NO3−(aq).

The synthesis and characterization of new zirconium permethylpentalene (form)amidinate complexes are described: Pn*Zr{N(Dipp)2CH}Cl (1), Pn* = η8-C8Me6 and Dipp = 2,6-iPr-C6H3; [Pn*Zr{N(p-tol)2CH}Cl]2 (2), p-tol = 4-Me-C6H4; [Pn*Zr{N(iPr)2CMe}Cl]2 (3); Pn*Zr{N(iPr)2CPh}Cl (4); Pn*Zr{N(4-Me-C6H4)2CH}2 (5); [Pn*Zr{N(iPr)2CCH2}]2 (6); and Pn*Zr{N(iPr)2CPh}(O-2,6,-Me-C6H3) (7). The monohalide derivatives 1–4 demonstrate considerable structural diversity as the nature of the (form)amidinate-supporting ligand is changed. While complexes with acidic backbone protons proved susceptible to deprotonation using mild bases, those without underwent straightforward salt metathesis reactions with alkali metal salts, leading to complexes [Pn*Zr{N(iPr)2CCH2}]2 (6) and Pn*Zr{N(iPr)2CPh}(O-2,6-Me-C6H3) (7). Preliminary slurry-phase ethylene polymerization studies are also reported using complexes 2, 4, 5, and 7 to gain a direct comparison to the highly active, yet electronically saturated, Pn*Zr(CpR)Cl catalyst family.

The synthesis and characterization of group 4 permethylpentalene (Pn* = C8Me6) hydride complexes are explored; in all cases, multimetallic hydride clusters were obtained. Group 4 lithium metal hydride clusters were obtained when reacting the metal dihalides with hydride transfer reagents such as LiAlH4, and these species featured an unusual hexagonal bipyramidal structural motif. Only the zirconium analogue was found to undergo hydride exchange in the presence of deuterium. In contrast, a trimetallic titanium hydride cluster was isolated on reaction of the titanium dialkyl with hydrogen. This diamagnetic, mixed valence species was characterized in the solid state, as well as by solution electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The structure was further probed and corroborated by density functional theory calculations, which illustrated the formation of a metal-cluster bonding orbital responsible for the diamagnetism of the complex. These permethylpentalene hydride complexes have divergent structural motifs and reactivity in comparison with related classical cyclopentadienyl analogues.

Bimodal polyethylene is generated from a single immobilized catalyst on a single support under a single set of reaction conditions without introducing chain transfer agents. Using rac-ethylenebis(1-indenyl)zirconium dichloride [(EBI)ZrCl2] immobilized on a nickel-containing layered double hydroxide (LDH) support produces two distinct molecular weight distributions. The ratio of these two distinct fractions can be tuned by varying the LDH support as well as by changing the reaction conditions.

Developing heterogeneous catalysts with identifiable catalytic sites provides opportunities to explore their structure–activity relationship. Covalent organic framework (COF) represents an emerging class of porous materials that have exhibited great potential in various applications. Herein, a single-site heterogeneous photocatalyst consisting of 2D COF ultrathin nanobelts coordinated with single Cu–O/N sites (defined as Cu–COF) is synthesized and investigated for visible-light-driven CO2 reduction. The relatively weak N and O binding sites from the imine and methoxy groups of the organic linkers result in active Cu–O/N sites for charge transfer and CO2 reduction. The resultant Cu–COF with 0.2 wt% Cu only serves as a bifunctional photocatalyst for visible-light-driven CO2 reduction in the absence of a photosensitizer with triethanolamine as the sacrificial reagent. A high CO selectivity of 94% is obtained. This study further demonstrates the great potential of COFs in heterogeneous catalysis with the abundant choices of functional groups in the organic linkers.

Qiang Wang, Heriberto Pfeiffer, Rose Amal, and Dermot O'Hare introduce the Reaction Chemistry & Engineering themed collection on CO2 capture, utilization and storage (CCUS).

We report the synthesis and characterisation of new permethylpentalene zirconium bis(amido) and permethylpentalene zirconium cyclopentadienyl mono(amido) complexes, and their reactivity with carbon dioxide.

We report an atom economic synthesis of a new type of dense porous layered double hydroxides (SLDHs) using struvite which is a commonly produced undesirable waste in wastewater treatment plants. The obtained SLDHs exhibit significantly higher specific surface areas and larger pore volumes than conventional coprecipitated LDHs but retain a comparable particle density.

High gas barrier, transparent and non-toxic coatings are in increasing demand due to the need to develop easier recyclable food packaging technologies. Herein, we report a green synthesis of layered double hydroxide (LDH) nanoplatelets via a reconstruction process in concentrated amino acid solution. The effect of both the amino acid (nonpolar and polar) and the original LDH morphology (rosette and large platelet) on the formation of uniform dispersed LDH nanoplatelets was systematically studied. LDH nanosheet dispersions in polyvinyl alcohol (PVA) were coated on polyethylene terephthalate (PET) substrates. The oxygen barrier performance and optical properties of the LDH nanosheet coated PET films were evaluated. We found that the PET coated films retained excellent optical responses and exhibited a high oxygen barrier, with an oxygen transmission rate down to 0.35 cc m−2 day−1. This represents an oxygen barrier improvement factor (BIF) between the coated and uncoated PET films of 175.

The development of future mobility (e.g. electric vehicles) requires supercapacitors with high voltage and high energy density. Conventional active carbon-based supercapacitors have almost reached their limit of energy density which is still far below the desired performance. Advanced materials, particularly metal hydroxides/oxides with tailored structure are promising supercapacitor electrodes to push the limit of energy density. To date, research has largely focused on evaluation of these materials in aqueous electrolyte, while this may enable high specific capacitance, it results in low working voltage window and poor cycle stability. Herein, we report the development of Ni2Mn-layered double oxides (Ni2Mn-LDOs) as mixed metal oxide-based supercapacitor electrodes for use in an organic electrolyte. Ni2Mn-LDO obtained by calcination of [Ni0.66Mn0.33(OH)2](CO3)0.175·nH2O at 400 °C produced the best performing Ni2Mn-LDOs with high working voltage of 2.5 V and a specific capacitance of 44 F g−1 (at 1 A g−1). We believe the performance of the Ni2Mn-LDOs is related to its unique porous structure, high surface area and the homogeneous mixed metal oxide network. Ni2Mn-LDO outperforms both the single metal oxides (NiO, MnO2) and the equivalent physical mixture of the two oxides. We propose this performance boost arises from synergy between NiO and MnOx due to a more effective homogeneous network of NiO/MnOx domains in the Ni2Mn-LDO. This work clearly shows the advantage of an LDO over the single component metal oxides as well as the physical mixture of mixed metal oxides and highlights the possibilities of development of further mixed metal oxides-based supercapacitors in organic electrolyte using LDH precursors.

Potassium-promoted layered double hydroxide (LDH)-derived materials are suitable elevated temperature CO2 adsorbents for pre-combustion CO2 capture. A challenge for the commercialization of LDHs as efficient CO2 adsorbents is their low capacities (ca. 0.5–0.6 mmol/g@400 °C) due to their hydrogen-bonded stacked structure. In this study, the aqueous miscible organic solvent treatment (AMOST) was used to exfoliate Mg3Al–CO3 LDH into nanosheets with a flower-like morphology, resulting in high surface areas of 287 and 212 m2/g for CC1 (washed with ethanol) and CC2 (washed with acetone), respectively. The exfoliated LDH structure exposed more interlayered CO2 active sites and promoters for alkali metal modification. Six impregnation solvents, water, acetone, ethanediol, ethanol, DMAC, and methanol were screened to optimize the CO2 uptake of 20 wt% K2CO3-promoted CC1. K2CO3/CC1(ed) using ethanediol as the impregnation solvent reached a CO2 working capacity of 1.46 mmol/g at 400 °C in the first cycle and 1.23 mmol/g after 10 cycles, twice the capacity of the commercial K2CO3/MG70. Material characterization indicated that the unexpectedly high performance of K2CO3/CC1(ed) could be attributed to the uniform K+ dispersion on the surface of K2CO3/CC1(ed) rather than bulk phase formation and the release of the residual solvent during calcination that could generate more paths for CO2 diffusion.

Three permethylindenyl zirconocenes have been supported on a hexane-insoluble form of polymethylaluminoxane modified with 40 wt % pentafluorophenol (sMAO(PFP)). The solid precatalysts were characterized by solid-state nuclear magnetic resonance spectroscopy, and their ethylene polymerization activity was studied. When supported on sMAO(PFP), Me2SB(Cp,I*)ZrX2 ({(η5-C9Me6)Me2Si(η5-C5H4)}ZrX2; X = Cl, CH2Ph, and Me) showed ethylene polymerization activities up to 25% higher than when supported on unmodified sMAO with the same [Al]0/[Zr]0 catalyst loading: activities of 6454 and 5144 kgPE molZr–1 h–1 bar–1 at 80 °C for Me2SB(Cp,I*)ZrCl2 supported on sMAO(PFP) and sMAO, respectively. The systems produced relatively low-molecular weight polyethylenes (Mw < 170 kg mol–1 at 80 °C) with minimal defects and branching. The polymers showed good flowability, although they displayed more aggregated morphologies than polyethylenes produced from unmodified sMAO. On increasing the solvent volume fivefold, the activity and polymer molecular weights approximately doubled.

The search for efficient amine-functionalized materials for direct air capture (DAC) of CO2 is highly important to achieve negative emissions. Here we report a new family of class 1 adsorbents for DAC by loading 67 wt% branched poly(ethylenimine) (PEI) onto Mg–Al–CO3 layered double hydroxide-derived mixed metal oxides (MMOs), which exhibit unexpectedly large CO2 uptakes (2.27 mmol g−1), fast kinetics (1.1 mmol g−1 h−1), and high stability over 20 cycles at 25 °C under 0.4 mbar CO2. The prepared MMO nanosheets are self-assembled into spherical shaped particles with abundant slit-like mesopores and broad pore size distribution. This ideal nanostructure leads to the uniform distribution of the impregnated PEIs and optimal accessibility for CO2 molecules. The defect-abundant MMO layers provide strong electrostatic attraction to the attached polyamines, making the hybrid adsorbents thermally robust up to 300 °C. Enhanced capacity and stability are observed in the presence of moisture, thus facilitating the use of steam stripping to concentrate the desorbed CO2.

Physicochemical surface-structure studies of highly active slurry-phase ethylene polymerisation catalysts has been performed. Zirconocene complexes immobilised on solid polymethylaluminoxane (sMAO) (sMAO–Cp2ZrX2), have been investigated using SEM-EDX, diffuse reflectance FT-IR (DRIFT) and high field (21.1 T) solid state NMR (ssNMR) spectroscopy. The data suggest a common surface-bound cationic methylzirconocene is the catalytically active species. 91Zr solid sate NMR spectra of sMAO–Cp2ZrCl2 and sMAO–Cp2ZrMe2 are consistent with a common surface-bound Zr environment. However, variation of the σ-donor (X) groups on the metallocene precatalyst leads to significant differences in polymerisation activity. We report evidence for X group transfer from the precatalyst complex onto the surface of the aluminoxane support, which in the case of X = C6F5, results in a 38% increase in activity.

Two-dimensional layered double hydroxides (LDHs) are currently a topic of significant interest due to their extraordinary physiochemical properties. LDHs are potentially useful in a wide range of applications, particularly in environmental, energy, catalysis, and biomaterials related fields. Despite the unique intrinsic properties of LDHs, various functionalization strategies have been applied to LDHs that yield even more exciting performance opportunities, offering guides to design novel functional nanomaterials. In this review, we address how these strategies can improve the various properties of LDHs. We provide an overview of the functionalizing strategies of intercalation, surface modification, hybridization, layered compositions regulation, size and morphology control, and defect creation. These strategies contribute significantly to the enhancement of the performance of LDHs, across a diverse range of areas such as adsorptive, catalytic, electronic, electrochemical, and optical. As a result, functionalized LDHs exhibit great potential in a wide range of applications in the environmental and energy domains. We have comprehensively highlighted their emerging potential in the environmental, energy, catalysis, and biomaterials related fields, including heavy metal removal, radionuclide capture, organic contaminants purification, oil pollution elimination, hydrogen generation, supercapacitors, batteries, solar cells, catalysis, and biomaterial fabrication.

The performance profile of a supported metallocene catalyst in slurry-phase ethylene polymerisation can be significantly enhanced by tuning the chemical composition of the support. By employing catalyst supports derived from zinc-containing layered double hydroxides (LDHs), the slurry phase ethylene polymerisation productivity of (EBI)ZrCl2 (EBI = rac-ethylenebis(indenyl)) can be quadrupled relative to a magnesium-containing support. Productivity increases approximately linearly with zinc content of the LDH before reaching a plateau; our experiments suggest the productivity of this catalyst system is related to the overall Lewis acidity of the support surface. We have found that iron-containing LDH supports with a similar overall Lewis acidity also result in productivity enhancements, demonstrating the general nature of this phenomena.

Direct air capture (DAC) is becoming a technically feasible negative emission technology; however, the fabrication of affordable adsorbents with large CO2 capacities, fast kinetics, and high sorption-desorption stability are of critical importance for the large-scale deployment of the DAC process. In this study, amine functionalized, aqueous miscible organic MgxAl-CO3 layered double hydroxide (LDH) nanosheets are used to efficiently and rapidly capture CO2 from ambient air. 3-[2-(2-Aminoethylamino)ethylamino]propyl-trimethoxysilane (TRI) treatment of highly dispersed LDH nanosheets produces a sorbent exhibiting an impressive adsorption capacity of 1.05 mmol g−1 at 25°C when exposed to 400 ppm CO2, which is 30% higher than equivalent amine-functionalized SBA-15 supports. CO2 uptake reaches 70% of this maximum capacity within 30 min and is twice as fast as supported polyamines. The highly dispersed LDH nanosheets provide excellent thermal, hydrothermal, and chemical stability, with negligible performance degradation after 50 adsorption-desorption cycles.

Whilst applying a coating layer to a polymer film is a routine approach to enhance the gas barrier properties of the film, it is counter-intuitive to consider that the gas barrier performance of the film would improve by ageing the coating dispersion for weeks before application. Herein, we report that the oxygen barrier performance of a 12 μm PET film coated with a dispersion of inorganic nanosheets in polyvinyl alcohol can be significantly enhanced by ageing this coating dispersion for up to 8 weeks before application. We found up to a 37-fold decrease in the oxygen transmission rate (OTR) of the PET coated film using aged dispersions of [Mg0.66Al0.33(OH)2](NO3)0.33 layered double hydroxide nanosheets (Mg2Al-LDH NS) in polyvinyl alcohol (PVA) compared to the film coated with an equivalent freshly prepared LDH/PVA dispersion. A limiting OTR value of 0.31 cc m−2 day−1 was achieved using the PET film coated with a 3 week aged LDH NS/PVA dispersion. X-ray diffraction experiments show that the degree of in plane alignment of LDH NS on the PET film surface increased significantly from 70.6 ± 0.6 to 86.7 ± 0.6 (%) (100% represents complete alignment of LDH NS platelets on the film surface) for the 4 week aged dispersion compared to the freshly prepared layer. We postulate that when the Mg2Al-LDH NS are aged in PVA the coiled PVA aggregates start to unwrap and attach onto the Mg2Al-LDH NS through hydrogen bonding and eventually form a hydrogen bonded ordered network that facilitates the alignment of nanosheet dispersions during the coating process. Our results suggest that the ageing of inorganic nanosheet dispersions in PVA or other potential hydrogen bonding adhesive systems could be a general approach to improve the alignment of the nanosheets on the polymer film surface once applied and thus improve their performance characteristics for barrier coating applications.

Novel permethylindenyl-phenoxide (PHENI*)ansa-metallocene titanium complexes have been synthesised and immobilised on inorganic solid supports to afford highly effective catalysts for slurry-phase ethylene polymerisation. When supported on solid polymethylaluminoxane these complexes were both extremely active (up to 3.7 × 106gPEmolTi−1h−1bar−1) and produced substantially disentangled polyethylene with a weight-average molecular weight (Mw) of 3.4 MDa (disUHMWPE).

The development of future mobility (

Chloride ion batteries (CIBs) are an example of a promising new emerging rechargeable battery technology, that exhibits large theoretical volumetric energy density performance and good safety. However, unsatisfactory capacity and poor cycling lifetime of the cathode currently hinder the development of CIBs. Herein, we report the use of an Ni2+Fe3+-based layered double hydroxide (LDH) intercalated by chloride ions as a promising cathode material for CIBs. [Ni2Fe(OH)6]Cl·1.37H2O (NiFe–Cl LDH) exhibits a high maximum capacity of 350.6 mA h g−1and a long lifetime of over 800 cycles (at 101.1 mA h g−1) at a current density of 100 mA g−1, which is superior to most currently reported CIB cathodes.In situX-ray absorption near-edge structure (XANES) andex situX-ray photoelectron spectroscopy (XPS) reveal the valency changes of the Fe2+/Fe3+and Ni2+/Ni3+redox pairs within the metal hydroxide layers of the LDH during electrochemcial cycling.In situXRD reveals that 2D anion diffusion within the LDH results in only ∼3% structural change. Oxygen K-edge soft X-ray absorption spectroscopy (SXAS) reveals the oxygen atoms within the MO6octahedra reversibly participate in the electrochemical reaction. In view of the extensive chemical variation, low-cost, and ease-of-preparation of LDH-based materials we regard LDHs as a promising materials platform for application as cathode materials in chloride ion batteries.

Solid polymethylaluminoxane (sMAO) supported ansa-bridged permethylindenyl zirconocenes Me2SB(CpR,I*)ZrX2 ({(η5-C9Me6)Me2Si(η5-C5H3R)}ZrX2; R = H, Me, and nBu; X = Cl, Br, Me, and CH2Ph) have been investigated as catalysts for the slurry-phase polymerization of ethylene in the presence of H2. The catalysts demonstrated remarkable stability to H2 both in a high-throughput screening system and in a 2 L batch reactor, with an almost constant ethylene uptake maintained throughout the polymerization runs. The catalysts demonstrated very high ethylene polymerization activities, almost 3 times higher than sMAO-(CpnBu)2ZrCl2 (industrial standard zirconocene catalyst) under the same conditions. The presence of small quantities of H2 (

CO₂ electroreduction using renewable electricity is a promising pathway for CO₂ utilization. However, the development of highly active and selective catalysts for CO₂ reduction still poses significant challenges. Here, we report the use of an amino-functionalized metal–organic framework as a precursor to derive Ni-N-C active sites embedded in multilayer graphene shells as the dominant active sites for CO₂ electroreduction. During the process of high-temperature annealing and acid washing, the −NH₂ groups in the MOF precursors exhibit a greater tendency to generate structural defects on graphene layers and derive abundant Ni-N-C sites by Ni migration. Aggregated Ni particles, which incline to catalyze the competitive hydrogen evolution reaction, are successfully removed during the posttreatment, exposing numerous Ni-N-C active sites to facilitate the CO₂ electroreduction. The resulting catalyst displays excellent electrochemical CO₂ reduction activity to CO with Faradaic efficiencies above 90% in a wide range of potentials from −0.6 to −1.2 V versus reversible hydrogen electrode. The maximum Faradaic efficiency of 97% can be achieved at a low overpotential of 0.79 V with a CO partial current density of 27.2 mA cm–², which is among the best performance of Ni-based electrocatalysts reported so far. This work provides useful insights into the tuning of the metal sites by the coordination environment of MOFs toward the fabrication of highly active and selective electrocatalysts for CO₂ reduction.

A zeolite@layered double hydroxide (LDH) core–shell hybrid (Z13X@Mg2Al–CO3 LDH) and a metal organic framework (MOF) MOF@LDH core–shell hybrid (Mg-MOF-74@Mg2Al–CO3 LDH) have been synthesised using a simple, scalable co-precipitation method. The effects of the synthesis parameters on the phase purity, crystallinity, morphology, composition, thermal stability, Brunauer–Emmett–Teller (BET) specific surface area and porosity of the core–shell hybrid have been investigated. Rapid metal nitrate addition was found to facilitate the growth of LDH shells with good crystallinity and thickness (250 nm). Ageing times of 0.5 and 16 hours were found to promote the formation of core@shell materials with high BET specific surface areas of 517 and 514 m2 g−1, respectively.

A new solvothermal post-synthesis treatment for preparing high aspect ratio magnesium aluminium layered double hydroxides (MgAl–LDHs) has been developed. Treating laurate-intercalated MgAl–LDHs in pure ethanol in an autoclave for 48 h at 150 °C was found to produce delaminated MgAl–LDH nanosheets with a thickness of ∼2.6 nm and an aspect ratio of ∼105. It is proposed that the high pressure solvothermal process promotes the insertion of ethanol molecules into the LDH interlayer space, thereby facilitating delamination. This new post-synthesis treatment provides the opportunity for a facile, large scale route to highly delaminated high aspect ratio LDHs, which might be of interest towards novel nanomaterials for energy conversion and storage.

Rac- and meso-bis(1-hexamethylindenyl)phenylborane zirconium dichloride, {rac-, meso-( Ph BBI*)ZrCl 2 } has been synthesised and fully characterised. The slurry phase ethylene polymerisation performance of rac-( Ph BBI*)ZrCl 2 immobilised on a range of methylaluminoxane (MAO)-modified, solvent-dispersed, high surface area layered double hydroxides (AMO/AIM-Mg x Al-CO 3 LDHs) have been studied. The polymerisation activities show a strong dependence on the nature of the LDH. Rac-( Ph BBI*)ZrCl 2 supported on a MAO-modified 1-hexanol dispersed [Mg 0.73 Al 0.27 (OH) 2 ][CO 3 ] 0.135 LDH displayed a maximum ethylene polymerisation activity of 6641 kg PE mol Zr−1 h −1 bar −1 at 70 °C and 2 bar ethylene. Benchmarking studies reveal that some of the rac-( Ph BBI*)ZrCl 2 supported catalysts outperform a range of commonly used industrial metallocene PE catalysts.

Recently, lithium containing ceramic based high-temperature CO 2 sorbents have received tremendous attention due to their high CO 2 capture capacity, low regeneration temperatures, and relatively high stability. With the rapid development of these promising CO 2 capturing materials, a timely review is highly demanded. In this contribution, we critically summarize the performance of all types of lithium containing ceramics including lithium silicates, zirconates, titanates, aluminates, ferrites, cuprates, bismuthates and borates for capturing CO 2 at high temperatures. For these CO 2 sorbents, all possible schemes for improving their CO 2 capture capacity, kinetics, and cycling stability have been comprehensively reviewed. Their potential applications in high-temperature post-combustion CO 2 capture from stationary flue gases, sorption enhanced methane steaming reforming, sorption enhanced alcohol reforming, and CO oxidation coupled with subsequent CO 2 capture processes are compared and discussed. We hope this work can inspire and guide researchers from a wide range of backgrounds and help pave the way for major breakthroughs in both fundamental studies and industrial applications in this field.

Polymetallocenes based on ferrocene, and to a lesser extent cobaltocene, have been well-studied, whereas analogous systems based on nickelocene are virtually unexplored. It has been previously shown that poly(nickelocenylpropylene) [Ni(η5 -C5 H4 )2 (CH2 )3 ]n is formed as a mixture of cyclic (6x ) and linear (7) components by the reversible ring-opening polymerisation (ROP) of tricarba[3]nickelocenophane [Ni(η5 -C5 H4 )2 (CH2 )3 ] (5). Herein the generality of this approach to main-chain polynickelocenes is demonstrated and the ROP of tetracarba[4]nickelocenophane [Ni(η5 -C5 H4 )2 (CH2 )4 ] (8), and disila[2]nickelocenophane [Ni(η5 -C5 H4 )2 (SiMe2 )2 ] (12) is described, to yield predominantly insoluble homopolymers poly(nickelocenylbutylene) [Ni(η5 -C5 H4 )2 (CH2 )4 ]n (13) and poly(tetramethyldisilylnickelocene) [Ni(η5 -C5 H4 )2 (SiMe2 )2 ]n (14), respectively. The ROP of 8 and 12 was also found to be reversible at elevated temperature. To access soluble high molar mass materials, copolymerisations of 5, 8, and 12 were performed. Superconducting quantum interference device (SQUID) magnetometry measurements of 13 and 14 indicated that these homopolymers behave as simple paramagnets at temperatures greater than 50 K, with significant antiferromagnetic coupling that is notably larger in carbon-bridged 6x /7 and 13 compared to the disilyl-bridged 14. However, the behaviour of these polynickelocenes deviates substantially from the Curie-Weiss law at low temperatures due to considerable zero-field splitting.

A new family of group 4 permethylpentalene (C8Me62−; Pn*) aryloxide and alkoxide complexes have been synthesised and fully characterised by multinuclear NMR spectroscopy and single-crystal X-ray diffraction; (η8-C8Me6)Zr(OR)2(R =tBu (1), 2,6-Me-C6H3(2), 2,6-iPr-C6H3(3) and 4-OMe-C6H4(4)), (η8-C8Me6)Zr (OR) (R = 2,6-tBu-C6H3(5) and 2,6-tBu-4-Me-C6H2(6)), (η8-C8Me6)ZrCp(OR) (R =tBu (7), 2,6-Me-C6H3(8) and 2,6-iPr-C6H3(9)), (η8-C8Me6)TiCp(O-2,6-Me-C6H3) (10) and (η8-C8Me6)ZrCpMe(OR) (R = 2,6-Me-C6H3(11), 2,6-iPr-C6H3(12) and 2,4-tBu-C6H3(13)).2,3,6,7,9,10and12were studied as initiators for the ring-opening polymerisation (ROP) ofL-lactide, and2,3,6,7and10were studied as initiators for the ROP ofrac-lactide.3was found to be the most active initiator for the ROP ofL-lactide (kobs= 0.35 h−1) and2for the ROP ofrac-lactide (kobs= 0.21 h−1). These initiators produced isotactic PLA for the ROP ofL-lactide and moderately heterotactic enriched (maximumProf 0.69) or atactic PLA for the ROP ofrac-lactide with polymer chains consisting of polylactic acid repeat units with –OR and –OH end groups.

We report the synthesis and characterisation of new permethylpentalene zirconium bis(amido) and permethylpentalene zirconium cyclopentadienyl mono(amido) complexes, and their reactivity with carbon dioxide.

A new family of zirconocene complexes of the type (3-RInd#)2ZrX2 (where Ind# = C6Me5H and R = Me, Et and Ph) have been synthesised and fully characterised. Six new crystal structures have been reported (meso-(3-EtInd#)2ZrBr2, rac-(3-EtInd#)2ZrCl2, rac-(3-EtInd#)2Zr(CH2Ph)2, meso-(3-EtInd#)2Zr(CH2Ph)2, meso-(3-MeInd#)2ZrBr2 and meso-(3-MeInd#)2Zr(CH2Ph)2). The complexes were studied for slurry-phase ethylene polymerisation when immobilised on solid polymethylaluminoxane (sMAO). Variation in the initiation group was found to have greater influence over polymerisation activity for meso-catalysts than rac-catalysts, with meso-alkyl catalysts showing higher polymerisation activities than meso-halide. Below 70 °C, polymerisation activity follows the order sMAO-meso-(3-EtInd#)2Zr(CH2Ph)2, sMAO-meso-(3-EtInd#)2ZrCl2 and sMAO-meso-(3-EtInd#)2ZrBr2 (activities of 657, 561, and 452 kgPE molM−1 h−1 bar−1, respectively). sMAO-meso-(3-EtInd#)2ZrBr2 produces HDPE with the highest molecular weight, followed by sMAO-meso-(3-EtInd#)2ZrCl2 and sMAO-meso-(3-EtInd#)2Zr(CH2Ph)2 (Mw of 503, 406, and 345 kg mol−1, respectively, at 50 °C). sMAO-meso-(3-MeInd#)2ZrBr2 produced HDPE with almost identical molecular weights to sMAO-meso-(3-EtInd#)2ZrCl2 (395 kg mol−1 at 50 °C).

A family of permethylindenyl titanium constrained geometry complexes, Me

Embargado hasta 12/09/2023 New efficient photocatalysts are required to remediate polluted urban atmospheres. We prepared a series of highly dispersed aqueous miscible organic (AMO) solvent treated NiTi layered double hydroxide (NixTi-AMO-LDHs (x = 2,3)) and studied their performance in the photocatalytic abatement of NOx gases. These photocatalysts can be prepared by a simple and scalable coprecipitation method at room temperature. NixTi-AMO-LDHs (x = 2,3) have been prepared with specific N2 BET surface areas and pore volumes up to to 492 m2g–1 and 1.37 cm3 g–1 respectively. Under sunlight simulation, the De-NOx performance of the conventional LDH and P25 (TiO2) benchmarks were surpassed by 40% and 17% respectively by the NixTi-AMO-LDHs. The NixTi-AMO-LDHs photocatalyst also exhibited outstanding reusability and unusually low release of the toxic NO2. The selectivity for the De-NOx process was investigated by in situ DRIFT measurements, the high surface area and pore volume was observed to play a significant role on the adsorption of the NO2 and N2O4 intermediates. The 2D character of the AMO-LDHs contributed to an enhancement in the production of radical species under illumination and reduction charge carrier recombination.

Recently, the Innovation Team of Energy-Water-Air (ITEWA) from Shanghai Jiao Tong University has carried out researches on direct air capture of CO2. A new family of amine functionalized DAC adsorbent was reported by impregnating branched polyethyleneimine onto mixed metal oxide nanosheets, which exhibits excellent CO2 adsorption capacity (2.27 mmol/g) and kinetics (1.1 mmol/g∙h) under 400 ppm CO2 as well as good thermal stability and hydrothermal stability with almost no performance degradation after 20 adsorption cycles (DOI: 10.1039/D0TA05079B). On this basis, a three-step steam-assisted temperature vacuum swing adsorption (S-TVSA) cycle was designed for DAC (DOI: 10.1016/j.rser.2020.110651). Simulation results show that the S-TVSA cycle could capture CO2 at a rate of 4.45 mol/kg·day. By using novel adsorbents with better adsorption capacities and kinetics, the capture rate can be further increased by 280% and the energy consumption reduced to 32.8%.

A series of modified solid polymethylaluminoxane (sMAO) catalyst supports have been developed for slurry phase ethylene polymerisation, using aryl di-ol modifier groups. Characterisation using ICP-MS analysis, X-ray total scattering, SEM–EDX, diffuse FT-IR and solid state NMR spectroscopy shows that the organic linker groups are uniformly distributed in a proposed organic framework stucture we call a “sMAOF”. When used as a support for rac-ethylene{bis(1-indenyl)} zirconium dichloride, (EBI)ZrCl2, these linker modified sMAOF materials provide a 40% enhancement in polymerisation activity with respect to unmodified sMAO: activities of 163 × 103 and 116 × 103 kgPE molZr−1 h−1 at 80 °C for (EBI)ZrCl2 supported on sMAOF(1,4-HO(C6F4)OH) and sMAO, respectively. The observed activity increase is correlated with the higher BET surface area and increased porosity in the linker modified sMAOF activating support.

Nowadays, it is greatly concerning the harmful effects provoked over the environment and citizens by the urban pollution of NOx (NO + NO2) gases. With the aim to remediate this problem, photocatalytic Layered Double Hydroxides (LDH) have been applied recently to remove these pollutants (De-NOx action) directly from the air. In this work, Ni2+Ti+4 -LDH with the interlayer anion carbonate have been synthesized by the coprecipitation method (NiTi-LDH). In addition to this preparation procedure, a treatment, AMOST (Aqueous Miscible Organic Solvent Treatment) has been applied to the samples in order to increase its surface area and particle dispersion (NiTi-AM samples). Moreover, two Ni/Ti ratios have been prepared to examine its effect on the De-NOx performance. The samples were characterized in order to study its structure, porosity, morphology, and optical properties. The obtained results showed that the NiTi-AM chemical structure did not change after the AMOST, but they showed a high increase of the delamination degree, leading to high specific surface area values. The photocatalytic De-NOx performance increases in those samples with higher amount of Ti (Ni/Ti = 2/1) and those subjected to the AMOST process. This process had more effect on the Ni/Ti = 3/1 ratio samples exhibiting improved photoactivity (≈ 10 %) compared to those samples prepared by conventional method. The enhanced De-NOx performance was associated to the higher number of LDH nanosheets, which increases the number of actives sites accessible to the reactant molecules.

Potassium salt prepared AMO-MgxAl-LDH(K) (x = 2–5) have been studied as catalyst precursors for biodiesel synthesis. Calcined potassium salt prepared [AMO-Mg0.75Al0.25(OH)2](CO3)0.17K0.01 {AMO-Mg3Al-LDH(K)} with high surface area (366.1 m2 g−1) and Lewis basicity density (2.87 μmol m−2) catalyses the transesterification of sunflower oil with methanol to yield fatty acid methyl esters (FAMEs) after 300 minutes (99%), a much higher performance than conventional LDHs.

We report the synthesis and characterisation of eight constrained geometry complexes, with variation of the amido fragment, ansa-bridge, permethylindenyl group, metal centre and initiator groups from the parent complex Me2SB(tBuN,I*)TiCl2. These complexes have been shown to be highly active for slurry-phase ethylene polymerisation when supported on solid polymethylaluminoxane (sMAO), with activities up to 7048 kgPE/molTi/h/bar. Ethylene/1-hexene and ethylene/styrene copolymerisations have shown these complexes to be good incorporators of comonomers into the polymer chain.