Biogenic volatile organic compounds in forest therapy base: A source of air pollutants or a healthcare function?

Air pollution poses a significant threat to public health, while biogenic volatile organic compounds (BVOCs) play a crucial role in both aspects. However, the unclear relationship between BVOCs and air pollutants in the under-canopy space limits the accuracy of air pollution control and the exploitation of forest healthcare functions. To clarify the variation of BVOCs in forest therapy bases, and their impacts on ozone (O3) and fine particulate matter (PM2.5) at nose height, total VOCs (TVOCs) in the forest were collected during typical sunny days, while air pollutants and meteorological factors were observed simultaneously. The results showed that the branch-level emissions of P. tabuliformis were dominated by healthcare-effective monoterpenoids, with only α-pinene having relative air concentrations of over 5 % in forest air samples. The correlation between concentrations of under-canopy TVOCs and emission rates of BVOCs from P. tabuliformis was weak (p > 0.09) in all seasons. However, the correlation between concentrations of TVOCs and the concentrations of O3 and PM2.5 showed clear seasonal differences. In spring, TVOCs only showed a significant negative correlation with PM2.5 in the forest (p < 0.01). In summer and autumn, TVOCs were significantly negatively correlated with both O3 (p < 0.001) and PM2.5 (p < 0.01). Specifically, the negative linear relationships were more pronounced for O3 and oxygenated VOCs in autumn (R2 = 0.40, p < 0.001) than for other relationships. The relationship between air pollutant concentrations inside and outside the forest also showed significant seasonal differences, generally characterized by a weaker correlation between them during seasons of strong emissions. Therefore, BVOCs in coniferous forests are health functions as they can provide healthcare effects and mitigate the concentration of air pollutants in the forest, and the establishment of forest therapy bases in rural areas with low NOx can be a sensible approach to promote good health, well-being, and sustainable development.

Circular olefin copolymers made de novo from ethylene and α-olefins.

Ethylene/α-olefin copolymers are produced in huge scale and widely used, but their after-use disposal has caused plastic pollution problems. Their chemical inertness made chemical re/upcycling difficult. Ideally, PE materials should be made de novo to have a circular closed-loop lifecycle. However, synthesis of circular ethylene/α-olefin copolymers, including high-volume, linear low-density PE as well as high-value olefin elastomers and block copolymers, presents a particular challenge due to difficulties in introducing branches while simultaneously installing chemical recyclability and directly using industrial ethylene and α-olefin feedstocks. Here we show that coupling of industrial coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks by polycondensation, affords a series of ester-linked PE-based copolymers. These new materials not only retain thermomechanical properties of PE-based materials but also exhibit full chemical circularity via simple transesterification and markedly enhanced adhesion to polar surfaces.

[Pollution Characteristics and Source Apportionment of VOCs in Urban Areas of Liaocheng in Summer].

Based on the online monitoring data of volatile organic compounds(VOCs) and ozone(O3) in Liaocheng in June 2021, the concentration levels, compositional characteristics, daily variation characteristics, and ozone formation potential(OFP) of VOCs on polluted days and clean days were systematically analyzed. Potential source areas of VOCs were identified by the potential source contribution function(PSCF) and concentration-weighted trajectory(CWT). The sources of VOCs in Liaocheng were analyzed using the characteristic species ratio and positive matrix factorization(PMF). The results showed that the hourly mean values of VOCs concentrations on polluted days and clean days in Liaocheng in June 2021 were(115.38±59.12) µg·m-3 and(88.10±33.04) µg·m-3, respectively, and the concentration levels of VOCs in each category showed that oxygenated volatile organic compounds(OVOCs)>alkanes>halogenated hydrocarbons>aromatic hydrocarbons>alkenes>alkynes>organosulfur. VOCs species with large differences in concentrations between polluted and clean days were among the top ten species of the hourly mean VOCs concentrations. The daily trends of concentrations of total VOCs, alkanes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons, and organosulfur showed that the daytime concentrations were lower than the nighttime concentrations, and the daily changes in OVOCs concentrations showed the characteristics of high in the daytime and low at nighttime. The OFP was 285.29 µg·m-3 on polluted days and 212.00 µg·m-3 on clean days, and OVOCs, alkenes, and aromatic hydrocarbons contributed significantly to ozone formation. The PSCF and CWT results found that the potential source areas of VOCs in Liaocheng were concentrated in the northern and northeastern part of Dongchangfu District and the central and southwestern part of Chiping District. The results of the characteristic species ratio indicated that the VOCs in Liaocheng might have been more from coal combustion, gasoline volatilization, and motor vehicle exhaust. The results of PMF showed that industrial emission sources(30.57%), motor vehicle exhaust and oil and gas volatilization sources(19.44%), combustion sources(17.23%), air aging and secondary generation sources(13.69%), solvent usage sources(12.75%), and natural sources(6.32%) were the main sources of VOCs in Liaocheng.

Design of Bifunctional Cu-SSZ-13@Mn2Cu1Al1Ox Core-Shell Catalyst with Superior Activity for the Simultaneous Removal of VOCs and NOx.

Synchronous control of volatile organic compounds (VOCs) and nitrogen oxides (NOx) is of great importance for ozone and PM2.5 pollution control. Balancing VOC oxidation and the NH3-SCR reaction is the key to achieving the simultaneous removal of these two pollutants. In this work, a vertically oriented Mn2Cu1Al1Ox nanosheet is grown in situ on the surface of Cu-SSZ-13 to synthesize a core-shell bifunctional catalyst (Cu-SSZ-13@Mn2Cu1Al1Ox) with multiple active sites. The optimized Cu-SSZ-13@Mn2Cu1Al1Ox catalyst delivered excellent performance for the simultaneous removal of VOCs and NOx with both 100% conversion at 300 °C in the presence of 5% water vapor. Physicochemical characterization and density functional theory (DFT) calculations revealed that Cu-SSZ-13@Mn2Cu1Al1Ox possesses more surface acidity and oxygen vacancies. The charge transfer between the core and shell is the intrinsic reason for the improved activity for both VOC and NOx removal. The molecular orbital theory is used to explain the different adsorption energies due to the different bonding modes between the core-shell and mixed individual catalysts. This work provides a novel strategy for designing efficient catalysts for the simultaneous removal of VOCs and NOx or other multiple pollutants.

The promoting/inhibiting effect of water vapor on the selective catalytic reduction of NOx.

In the field of nitrogen oxides (NOx) abatement, developing selective catalytic reduction (SCR) catalysts that can operate stably in the practical conditions remains a big challenge because of the complexity and uncertainty of actual flue gas emissions. As water vapor is unavoidable in the actual flue gas, it is indispensable to explore its effect on the performance of SCR catalysts. Many studies have proved that the effects of H2O on de-NOx activity of SCR catalysts were indeed observed during SCR reactions operated under wet conditions. Whether the effect is promotive or inhibitory depends on the reaction conditions, catalyst types and reducing agents used in SCR reaction. This review focuses on the effect of H2O on SCR catalysts and SCR reaction, including promoting effect, inhibiting effect, as well as the effecting mechanism. Besides, various strategies for developing a water-resistant SCR catalyst are also included. We hope that this work can give a more comprehensive insight into the effects of H2O on SCR catalysts and help with the rational design of water-resistant SCR catalysts for further practical application in NOx abatement field.

Unravelling the Mechanism of Intermediate-Temperature CO2 Interaction with Molten-NaNO3 -Salt-Promoted MgO.

The optimization of MgO-based adsorbents as advanced CO2 -capture materials is predominantly focused on their molten-salt modification, for which theoretical and experimental contributions provide great insights for their high CO2 -capture performance. The underlying mechanism of the promotion effect of the molten salt on CO2 capture, however, is a topic of controversy. Herein, advanced experimental characterization techniques, including in situ environmental transmission electron microscopy (eTEM) and CO2 chemisorption by diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), transient 18 O-isotopic exchange, and density functional theory (DFT), are employed to elucidate the mechanism of the CO2 interaction with molten-salt-modified MgO in the 250-400 °C range. Herein, eTEM studies using low (2-3 mbar) and high (700 mbar) CO2 pressures illustrate the dynamic evolution of the molten NaNO3 salt promoted and unpromoted MgO carbonation with high magnification (<50 nm). The formation of 18 O-NaNO3 (use of 18 O2 ) and C16 O18 O following CO2 interaction, verifies the proposed reaction path: conversion of NO3 - (NO3 -  â†’ NO2 +  + O2- ), adsorption of NO2 + on MgO with significant weakening of CO2 adsorption strength, and formation of [Mg2+ … O2- ] ion pairs preventing the development of an impermeable MgCO3 shell, which largely increases the rate of bulk MgO carbonation.

Electrochemical Reduction of CO2 to CO over Transition Metal/N-Doped Carbon Catalysts: The Active Sites and Reaction Mechanism.

Electrochemical CO2 reduction to value-added chemicals/fuels provides a promising way to mitigate CO2 emission and alleviate energy shortage. CO2 -to-CO conversion involves only two-electron/proton transfer and thus is kinetically fast. Among the various developed CO2 -to-CO reduction electrocatalysts, transition metal/N-doped carbon (M-N-C) catalysts are attractive due to their low cost and high activity. In this work, recent progress on the development of M-N-C catalysts for electrochemical CO2 -to-CO conversion is reviewed in detail. The regulation of the active sites in M-N-C catalysts and their related adjustable electrocatalytic CO2 reduction performance is discussed. A visual performance comparison of M-N-C catalysts for CO2 reduction reaction (CO2 RR) reported over the recent years is given, which suggests that Ni and Fe-N-C catalysts are the most promising candidates for large-scale reduction of CO2 to produce CO. Finally, outlooks and challenges are proposed for future research of CO2 -to-CO conversion.

Direct copolymerization of ethylene with protic comonomers enabled by multinuclear Ni catalysts.

Ethylene/polar monomer coordination copolymerization offers an attractive way of making functionalized polyolefins. However, ethylene copolymerization with industrially relevant short chain length alkenoic acid remain a big challenge. Here we report the efficient direct copolymerization of ethylene with vinyl acetic acid by tetranuclear nickel complexes. The protic monomer can be extended to acrylic acid, allylacetic acid, ω-alkenoic acid, allyl alcohol, and homoallyl alcohol. Based on X-ray analysis of precatalysts, control experiments, solvent-assisted electrospray ionization-mass spectrometry detection of key catalytic intermediates, and density functional theory studies, we propose a possible mechanistic scenario that involves a distinctive vinyl acetic acid enchainment enabled by Ni···Ni synergistic effects. Inspired by the mechanistic insights, binuclear nickel catalysts are designed and proved much more efficient for the copolymerization of ethylene with vinyl acetic acid or acrylic acid, achieving the highest turnover frequencies so far for both ethylene and polar monomers simultaneously.

Preparation of ammonium polyphosphate and dye co-intercalated LDH/polypropylene composites with enhanced flame retardant and UV resistance properties.

In this paper, ammonium polyphosphate (APP) with flame retardant performance and acid red 88 (AR88) with UV absorption property were intercalated into layered double hydroxide (LDH) interlayers together, aiming to improve the flame retardancy and UV resistance properties of polypropylene (PP) simultaneous in one system. The synthesized LDHs and PP/LDH composites were characterized systematically and the results showed that AR88 and APP were intercalated into LDH interlayers successfully, and the content of APP and AR88 in LDH interlayers can be controlled through the synthesis process. Both APP-LDHs and AR88/APP-LDHs can greatly improve the flame retardancy performance of PP, with 25 wt% LDH addition, the peak heat release rate (PHRR) decreased by 42-63%, respectively. Temperature at 50% mass loss (T50) of PP also increased to some extent. In addition, the intercalation of AR88 in LDH also possessed good UV adsorption which can delay the ageing of PP during their use. Thus, a new approach to improve both flame retardant and UV resistance properties for polymers at the same time is achieved.

Industrial carbon dioxide capture and utilization: state of the art and future challenges.

Dramatically increased CO2 concentration from several point sources is perceived to cause severe greenhouse effect towards the serious ongoing global warming with associated climate destabilization, inducing undesirable natural calamities, melting of glaciers, and extreme weather patterns. CO2 capture and utilization (CCU) has received tremendous attention due to its significant role in intensifying global warming. Considering the lack of a timely review on the state-of-the-art progress of promising CCU techniques, developing an appropriate and prompt summary of such advanced techniques with a comprehensive understanding is necessary. Thus, it is imperative to provide a timely review, given the fast growth of sophisticated CO2 capture and utilization materials and their implementation. In this work, we critically summarized and comprehensively reviewed the characteristics and performance of both liquid and solid CO2 adsorbents with possible schemes for the improvement of their CO2 capture ability and advances in CO2 utilization. Their industrial applications in pre- and post-combustion CO2 capture as well as utilization were systematically discussed and compared. With our great effort, this review would be of significant importance for academic researchers for obtaining an overall understanding of the current developments and future trends of CCU. This work is bound to benefit researchers in fields relating to CCU and facilitate the progress of significant breakthroughs in both fundamental research and commercial applications to deliver perspective views for future scientific and industrial advances in CCU.

Bis-Ferrocenyl-Pyridinediimine Trinuclear Mixed-Valent Complexes with Metal-Binding Dependent Electronic Coupling: Synthesis, Structures, and Redox-Spectroscopic Characterization.

A family of metal dichloride complexes having a bis-ferrocenyl-substituted pyridinediimine ligand was systematically synthesized ((Fc2PDI)MCl2, M = Mg, Zn, Fe, and Co) and characterized crystallographically, spectroscopically, electrochemically, and computationally. Electronic coupling between the ligand ferrocene units is switched on upon binding to a MCl2 fragment, as evidenced by both sequential oxidation of the ferrocenes in cyclic voltammetry (ΔEox ≈ 200 mV) and by Inter-Valence Charge Transfer electronic excitations in the near IR. Additionally, UV-vis spectra are used to directly observe orbital mixing between the ferrocenyl units and the imine π system since breaking of the orbital symmetry results in allowed transitions (ϵ = 2800 M-1cm-1 vs ϵ ≈ 200 M-1cm-1 in free ferrocene) as well as broadening and red-shifting of the ferrocenyl transitions-indicating organic character in formerly pure metal-centered transitions. DFT analysis reveals that interaction between the ferrocenes and the MCl2 fragment is small and suggests that communication is mediated by better energy matching between the ferrocene and organic π* orbitals upon coordination, allowing superexchange coupling through the LUMO. Furthermore, single crystal diffraction data obtained from oxidation of one and both ferrocenes show distortions, introducing the empty dxy/dx2-y2 orbitals into the secondary coordination sphere of the MCl2 fragment. Such structural rearrangements are infrequent in ferrocenyl mixed-valent compounds, and implications for catalysis as well as electronic communication are discussed.

Preparation of MnO2 decorated Co3Fe1Ox powder/monolithic catalyst with improved catalytic activity for toluene oxidation.

In this paper, KMnO4 was used to pre-treat Co3Fe-layered double hydroxides (LDH) precursor to prepare MnO2 decorated Co3Fe1Ox catalyst. The toluene oxidation performance of the catalyst was investigated systematically. The optimized 0.1MnCF-LDO catalyst exhibited the best catalytic performance, and the temperatures of 50% and 90% toluene conversion (T50 and T90) were 218 and 243°C, respectively. The apparent activation energy (Ea) was 31.6 kJ/mol. The characterization results showed that the pre-redox reaction by KMnO4 could increase the specific surface area, Co3+ species amount and oxygen defect concentration of the catalyst, which are the main reason of the improved toluene catalytic activity. Besides, this method was also applied to enhance toluene oxidation of iron mesh based monolithic catalyst. The 0.1MnCF-LDO/Iron mesh (IM) catalyst showed a 90% toluene conversion at around 316°C which was much lower than that of without MnO2 addition (359°C). In addition, the water resistant of all the catalysts was studied as well, all the samples showed relatively good water resistance. The toluene conversion still remained to be over >80% even in the presence of 10 vol.% water vapor.

Experimental and theoretical evidence for hydrogen doping in polymer solution-processed indium gallium oxide.

The field-effect electron mobility of aqueous solution-processed indium gallium oxide (IGO) thin-film transistors (TFTs) is significantly enhanced by polyvinyl alcohol (PVA) addition to the precursor solution, a >70-fold increase to 7.9 cm2/Vs. To understand the origin of this remarkable phenomenon, microstructure, electronic structure, and charge transport of IGO:PVA film are investigated by a battery of experimental and theoretical techniques, including In K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS); resonant soft X-ray scattering (R-SoXS); ultraviolet photoelectron spectroscopy (UPS); Fourier transform-infrared (FT-IR) spectroscopy; time-of-flight secondary-ion mass spectrometry (ToF-SIMS); composition-/processing-dependent TFT properties; high-resolution solid-state 1H, 71Ga, and 115In NMR spectroscopy; and discrete Fourier transform (DFT) analysis with ab initio molecular dynamics (MD) liquid-quench simulations. The 71Ga{1H} rotational-echo double-resonance (REDOR) NMR and other data indicate that PVA achieves optimal H doping with a Ga···H distance of ∼3.4 Å and conversion from six- to four-coordinate Ga, which together suppress deep trap defect localization. This reduces metal-oxide polyhedral distortion, thereby increasing the electron mobility. Hydroxyl polymer doping thus offers a pathway for efficient H doping in green solvent-processed metal oxide films and the promise of high-performance, ultra-stable metal oxide semiconductor electronics with simple binary compositions.

Polyethylene Terephthalate Deconstruction Catalyzed by a Carbon-Supported Single-Site Molybdenum-Dioxo Complex.

Polyethylene terephthalate (PET) is selectively depolymerized by a carbon-supported single-site molybdenum-dioxo catalyst to terephthalic acid (PTA) and ethylene. The solventless reactions are most efficient under 1 atmosphere of H2 . The catalyst exhibits high stability and can be recycled multiple times without loss of activity. Waste beverage bottle PET or a PET + polypropylene (PP) mixture (simulating the bottle + cap) proceeds at 260 °C with complete PET deconstruction and quantitative PTA isolation. Mechanistic studies with a model diester, 1,2-ethanediol dibenzoate, suggest the reaction proceeds by initial retro-hydroalkoxylation/ß-C-O scission and subsequent hydrogenolysis of the vinyl benzoate intermediate.

Polar Isotactic and Syndiotactic Polypropylenes by Organozirconium-Catalyzed Masking-Reagent-Free Propylene and Amino-Olefin Copolymerization.

Polar functionalized isotactic and syndiotactic polypropylenes (PPs) are synthesized by direct, masking-reagent-free propylene and amino-olefin (AO, CH2 =CH(CH2 )x Nn Pr2 , x=2, 3, 6) copolymerizations using the activated precatalysts rac-[Me2 Si(indenyl)2 ]ZrMe2 and [Me2 C(Cp)(fluorenyl)]ZrMe2 , respectively. Polymerization activities at 25 °C are as high as 4208 and 535 kg/(mol h atm) with AO incorporation up to 4.0 mol % and 1.6 mol %, respectively. Remarkably, introducing the amino-olefin comonomers significantly enhances stereoselection for both isotactic (mmmm: 59.5 %→91.0 %) and syndiotactic (rrrr: 66.3 %→81.3 %) products.

Early Transition Metal Catalysis for Olefin-Polar Monomer Copolymerization.

Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentially upgrading polyolefins for advanced, value-added applications. The metal catalyst-mediated copolymerization of non-polar olefins with polar comonomers represents the seemingly most straightforward, atom- and energy-efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)-catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, largely associated with the Lewis basicity of the polar co-monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this Minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechanistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them.

A comparative study on the NOx storage and reduction performance of Pt/Ni1Mg2Al1Ox and Pt/Mn1Mg2Al1Ox catalysts.

A series of Ni1Mg2Al1Ox, Mn1Mg2Al1Ox, 0.5Pt/Ni1Mg2Al1Ox and 0.5Pt/Mn1Mg2Al1Ox catalysts were carefully prepared and their NOx storage and reduction (NSR) performance including NOx oxidation efficiency (NOE), NOx storage capacity (NSC), NOx conversion rate (XNO), N2 selectivity (SN2), N2O selectivity (SN2O) and NH3 selectivity (SNH3), was systematically investigated. A SO2 resistance test was also performed in the presence of 100 ppm SO2. The NOE and NSC experimental results revealed that the Ni1Mg2Al1Ox catalyst possesses a higher NSC, while the Mn1Mg2Al1Ox catalyst possesses a better NOE. With regard to XNO, 0.5Pt/Ni1Mg2Al1Ox presented higher results at 200 °C and 400 °C, while 0.5Pt/Mn1Mg2Al1Ox obtained the highest result at 300 °C, which was more than 60% for both. In addition, compared to 0.5Pt/Ni1Mg2Al1Ox, 0.5Pt/Mn1Mg2Al1Ox exhibited a relatively higher SN2 and lower SN2O and SNH3. The NOx-TPD and H2-TPSR results indicated that NOx adsorbed on Ni1Mg2Al1Ox and 0.5Pt/Ni1Mg2Al1Ox is more stable, and that NH3 can be formed in large amounts in a lower temperature range. Both Pt-containing catalysts presented a quite stable XNO in ten cycles in the presence of 100 ppm SO2, and their SN2 can be remarkably enhanced to more than 80%, which could be attributed to the reactions of NH3-SCR and SO2 + NH3. We believe this new insight can provide a new way of thinking for the development of NSR catalysts.

Synthesis of ZSM-5/Siliceous Zeolite Composites for Improvement of Hydrophobic Adsorption of Volatile Organic Compounds.

In this research, we investigated the hydrophobicity and dynamic adsorption-desorption behaviors of volatile organic compounds (VOCs) by applying different optimized coating dosage (25, 50, and 75%) on designed novel ZSM-5/MCM-41 and ZSM-5/Silicalite-1 hierarchical composites. The relatively large specific surface area and pore volume of adsorbents ZSM-5/MCM-41 and ZSM-5/Silicalite-1 composites with excellent stability were affirmed by ex-situ XRD, FTIR, BET, SEM, and water contact angle analyses. Regarding, toluene adsorption-desorption investigation, ZSM-5/MCM-41 composite lead a longer stable toluene breakthrough time no matter under dry or 50% humid conditions. However, under different loading dosage condition, the breakthrough time of 75% coating ratio was the longest, which was 1.6 times as long as that of pure ZSM-5 under wet adsorption. Meanwhile, the complete elimination of toluene for ZSM-5/MCM-41-75% was done by largest desorption peak area and the lowest desorption temperature of 101.9°C, while, the largest contact angle of ZSM-5/MCM-41-75% was 17.0° higher than pure ZSM-5 zeolite. Therefore, we believe that the present hydrophobic sorbent will provide new insight with great research potential for removing low concentration of VOCs at industrial scale.

Unexpected Precatalyst σ-Ligand Effects in Phenoxyimine Zr-Catalyzed Ethylene/1-Octene Copolymerizations.

Recent decades have witnessed intense research efforts aimed at developing new homogeneous olefin polymerization catalysts, with a primary focus on metal-Cl or metal-hydrocarbyl precursors. Curiously, metal-NR2 precursors have received far less attention. In this contribution, the Zr-amido complex FI2ZrX2 (FI = 2,4-di- tert-butyl-6-((isobutylimino)methyl)phenolate, X = NMe2) is found to exhibit high ethylene polymerization activity and relatively high 1-octene coenchainment selectivity (up to 7.2 mol%) after sequential activation with trimethylaluminum, then Ph3C+B(C6F5)4-. In sharp contrast, catalysts with traditional hydrocarbyl ligands such as benzyl and methyl give low 1-octene incorporation (0-1.0 mol%). This unexpected selectivity persists under scaled/industrial operating conditions and was previously inaccessible with traditional metal-Cl or -hydrocarbyl precursors. NMR, X-ray diffraction, and catalytic control experiments indicate that in this case an FI ligand is abstracted from FI2Zr(NMe2)2 by trimethylaluminum in the activation process to yield a catalytically active cationic mono-FIZr species. Heretofore this process was believed to serve only as a major catalyst deactivation pathway to be avoided. This work demonstrates the importance of investigating diverse precatalyst monodentate σ-ligands in developing new catalyst systems, especially for group 4 olefin polymerization catalysts.