Acetate Substrate Research Articles

Bioinspired dopamine modulating graphene oxide nanocomposite membrane interposed by super-hydrophilic UiO-66 with enhanced water permeability

A composite material constructed by intercalating super-hydrophilic UiO-66 into the graphene oxide (GO) nanosheets was synthesized under the modification of polydopamine (PDA), and the PDA/RGO/UiO-66 hybrid membranes with enhanced water permeability, favorable dye separation performance and anti-fouling property were prepared on the cellulose acetate (CA) substrate by vacuum-assisted filtration method. In this work, UiO-66 nanoparticles (NPs) were introduced into the GO interlayers to inhibit their accumulation, while PDA was used to partially reduce GO and ensure the stability of the composite material. The prepared powder samples and composite membranes were subjected to PXRD, FT-IR, SEM, AFM, XPS, WCA characterizations and zeta potential tests, respectively. The results indicated that PDA/RGO/UiO-66 complex films presented more hydrophilicity with a pure water flux as high as 167.14 L/(m2·h), which increased by 256.91% compared to the PDA/RGO membrane and maintained a high dye separation performance (99.54% for MB and 87.36% for CR). Also, the improvement in surface hydrophilicity of the membrane was advantageous for heightening its fouling resistance. In general, the PDA/RGO/UiO-66 composite membranes synthesized in this paper have great potential for efficient separation and purification of dye wastewater.

Effects of Different Substrates on MEC Anode Film Formation and Extracellular Polymer

In this paper, a single-cell microbial electrolysis cell (MEC) reactor is used, with activated sludge as the inoculum, glucose, sodium acetate, sodium propionate and sodium butyrate as substrates. The MEC anode film formation and the different nutritional conditions are studied for the influence of extracellular polymers. Experimental research shows that MECs running on different substrates show obvious current density and anode membrane electrochemical activity. MEC anode membrane current density of sodium acetate substrate culture is the highest (12.78 A/m2), followed by glucose and butyl Sodium and sodium propionate. MEC anode electroactive microorganisms can use a wide range of substrates. The energy efficiency of different substrates is different, and the energy efficiency of acetic acid is the highest. The electrochemical activity and hydrogen yield of the anode biofilm are the same as those of the MEC current density. Increasing the inoculum within a certain range is conducive to improving the electrochemical activity of the anode biofilm and the hydrogen yield of the anode film. Further analysis of the composition of the anode membrane biomass and extracellular polymer (EPS) showed that increasing the inoculation amount is beneficial to the increase of the anode membrane biomass. A large number of anode-attached bacteria can produce higher current density and EPS content. The protein in the anode membrane EPS The content is significantly higher than polysaccharides, and as the protein content increases, the electrical density also increases.

Brønsted Acid-Catalyzed Aza-Ferrier Reaction of N,O-Allenyl Acetals: Synthesis of β-Amino-α-methylene Aldehydes

A Tf2NH-catalyzed aza-Ferrier reaction of N,O-allenyl acetals was reported. This protocol provided various types of β-amino-α-methylene aldehydes as the products. The N,O-allenyl acetal substrates were easily prepared by base-induced isomerization of N,O-propargyl acetals with Triton B. The N,O-propargyl acetals were prepared from the corresponding aldehydes or lactams. Further synthetic applications of the products were also described.

The impact of temperature on the metabolism of volatile fatty acids by polyphosphate accumulating organisms (PAOs)

This study investigated the effects of different carbon sources on enriched Accumulibacter PAO cultures at high temperature (30 °C) and compared the carbon transformation with low temperature (20 °C) cases reported in literature, revealing several key metabolic differences. While PAOs seemed to prefer propionate anaerobically as compared to other VFAs at high temperature, high aerobic glycogen replenishment was realized with propionate as the anaerobic carbon source, a trait not previously observed at low temperatures. Therefore, it was found that propionate is not correlated with high P removal by Accumulibacter PAO at high temperatures. A combined substrate of acetate, propionate and perhaps butyrate seemed to be a better carbon source combination, since the total VFA uptake rate increased by up to 46%, and this increased the aerobic P-removal efficiency by up to 38.4% and reduced the glycogen recovery by more than 63% compared to the use of only propionate as substrate. This study improves our understanding of how to stimulate successful EBPR operation in warm climates by augmenting the P removal performance of PAOs.

Scratching and transplanting of electro-active biofilm in fruit peeling leachate by ultrasound: re-inoculation in new microbial fuel cell for enhancement of bio-energy production and organic matter detection.

An electro-active biofilm of Fruit Peeling (FP) leachate was formed onto the Carbon Felt (CF) bio-anode in a Microbial Fuel Cell (MFC), after functioning for a long time. The electro active-biofilm thus formed was then scratched by ultrasound and re-inoculated in a new leachate to be transplanted onto the bio-anode. This procedure allowed the microbial electron charge transfer and therefore the enhancement of the bio-energy production of the fuel cell. By using the repetitive mechanical biofilm removal, re-suspension and electrochemically facilitated biofilm formation, the voltage was substantially increased. In effect, the voltage of the 1st G of biofilm, rose gradually and reached its maximum value of 65mV after 10days. Whilst the 2nd generation allowed to obtain the maximum voltage 276mV and without any lag time. The DCO abatement using the 1st G biofilm was 68% greater than the 3rd G 26%. Besides, the electrochemical impedance spectroscopy characterization and cyclic voltammetry of bio-anode with 2nd G biofilm confirmed the ability of electro-active biofilm formation on a new support. The biofilm transplanted showed thus greater kinetic performance, with reduced lag time demonstrating the interest of the selection that took place during the formation of successive biofilms. Despite the transplantation of the electro-active biofilm onto the bio-anode, the MFC still produced relatively lower power output. Nevertheless, it has been tested successfully for monitoring and detecting the oxidation of sodium acetate substrate in the very wide concentration range 0.0025-35g/l.

Constructing substrate of low structural parameter by salt induction for high-performance TFC-FO membranes

Forward osmosis (FO) is a promising membrane-based technology for water treatment and desalination. But, internal concentration polarization (ICP), a unique phenomenon in FO, generally leads to the sharp performance decline. In this study, a novel polyacrylonitrile (PAN) substrate with low polymer concentration (4 wt%) of the thin-film composite (TFC) membrane with a low membrane structural parameter (S) is developed with sodium chloride (NaCl) aqueous solution as the coagulation bath, and exhibits high performance for FO applications. The existence of NaCl in the coagulation bath not only affects the phase inversion process significantly, resulting in the formation of a thin substrate with finely tuned morphology structure, but also benefits the formation of a uniform and defect-free top polyamide (PA) layer. Effects of NaCl content in the coagulation bath on the morphology and intrinsic properties of resulting PAN substrates, the formed PA layer, as well as the morphology and FO performance of resulting TFC membranes, are investigated systematically. Moreover, an extended study on cellulose acetate (CA) substrate is also conducted to study the universality of this salt induction method to fabricate high-performance TFC membranes. Compared to the control TFC membrane, modified TFC membranes show much lower S parameters and superior separation performance with the higher water flux (324% increment) and lower reverse salt flux (58% reduction).

Aedes aegypti vector resistance status on malation and activity of non specific esteration enzymes in Tembalang district, Semarang city

Background: Controlling of dengue vectors around dengue haemorrhagic fever cases is often conducted by using insecticides, including a malathion insecticide in the city of Semarang. A research on susceptibility status of Ae. aegypti to insecticides, used for fogging and based on a high number of hemorrhagic fever cases in Tembalang district, Semarang city, needs to be observed. Objective: This study aimed to determine resistance status of Ae. aegypti mosquitoes based on bioassay and biochemical tests of esterase non-specific enzyme activity in the Tembalang District. Methods: This study used a cross sectional design, it was conducted in June-September 2018 in a population of Aedes sp. from Tembalang District, Semarang City. Samples of F2 generations of female Ae. aegypti were obtained by ovitraps in the Tembalang District consisting of 12 urban villages, and their resistance status were tested by impregnated paper bioassay with malathion at a diagnostic dose of 0.8%. Esterase enzyme activity in the Ae. aegypti mosquito body of this population was tested biochemically to prove an increase in a non-specific esterase enzyme on the a-naphthyl acetate substrate. Results: The bioassay results showed that mortality rates of Ae. aegypti at the 12 villages in Tembalang district after 24 hourtest by impregnated paper indicated a range of 0-62%. Mechanism of resistance indicating an increase of non-specific enzyme esterase activity on a-naphthyl acetate at Rowosari, Kedungmundu, Sambiroto, and Meteseh could not be seen, It began to be seen in a low percentage (15%) at Sendang Mulyo, Tandang, Sendangguwo and Bubusan, and in a moderate percentage (45-75%) in Tembalang, Jangli and Mangunharjo. The mechanism of high esterase enzyme activity could be seen in the Ae. aegypti population at Kramas with AV=0,700-0,900 by a percentage of 20%, and AV=0,900 by a percentage of 80%. Conclusion: This study provided information about some Ae. aegypti mosquitoes from Tembalang District that showed resistance to the malathion insecticide with an elevation of non-specific esterase enzyme activity ona-naphthyl acetate substrate in several villages except Kelurahan Rowosari, Kedungmundu, Sambiroto, and Meteseh.

Investigation of growth kinetics and partial denitrification performance in strain Acinetobacter johnsonii under different environmental conditions.

A denitrifying strain ZY04 with a high nitrite-accumulating rate was isolated and purified from activated sludge in a laboratory-scale A2/O reactor. The strain was characterized and identified as Acinetobacter johnsonii by 16S rDNA phylogenetic analysis. The sequences of the key functional genes (napA, nirB, nirD) involved in partial denitrification were amplified via polymerase chain reaction, which provided a basis for exploring gene expression. The effects of different environmental factors (C/N ratio, pH and temperature) on the partial denitrification performance and transcriptional levels of the functional genes during the logarithmic growth phase were investigated by batch experiments. The results showed that the partial denitrification performance was optimal when the C/N ratio was 5, the pH value was 6–8 and the temperature was 25°C. The gene expression during the logarithmic growth phase indicated the good performance of partial denitrification under different environmental conditions. All three functional genes exhibited the highest expression levels at 25°C. The results of inhibitory kinetics analysis revealed that three biokinetic models (Aiba, Edwards and Andrews) simulated the growth pattern of strain ZY04 inhibited by a single substrate (nitrate or sodium acetate) well. In the double-substrate inhibitory model, five models of nine combinations successfully fitted the growth characteristics of the strain affected by the double substrate of nitrate and sodium acetate. The relevant semi-saturation parameters and substrate inhibition parameters were obtained, and the correlation coefficient (R2) reached 98%.

A biorefinery approach to bioethanol and bioelectricity co-production from tropical seaweeds

The use of biomass in biofuel production is known to harness only a fraction of the entire biomass leading to the generation of large quantities of waste. This underutilisation of biomass has become a major challenge in the development of biofuels, such as bioethanol, as an economical and eco-friendly alternative to fossil fuels. In this study, the algae Ulva fasciata, Hydropuntia dentata and Sargassum vulgare harvested from Ghanaian coasts were used for the co-production of bioethanol and bioelectricity using an integrated biorefinery approach as a means to maximise substrate use. The study obtained ethanol yields of 5.1, 3.7 and 2.4 g (100 g)−1 DM from U. fasciata, S. vulgare and H. dentata, respectively using Ambrosiozyma angophorae and various strains of Saccharomyces cerevisiae (SI17, C8T17, FT17 and PT17) as fermenting organisms. Seaweed bioethanol production residues obtained were used as substrates in microbial fuel cells to generate electric power densities of up to 0.50 W m−3, which were comparable to sodium acetate substrate by up to 52.6% with substantial substrate removal efficiencies of up to 46%. The novel co-production of bioethanol and bioelectricity from seaweeds successfully reduced waste generation to as low as 24.4% from a potential 69 to 79% from seaweed bioethanol production alone. The waste generated in the form of effluents from seaweed-residue-fed MFCs can be considered for soil amendment due to their ammonia content of up to 26%.

Photocatalytic Reductive Formation of α-Tertiary Ethers from Ketals.

A general photocatalytic reductive strategy for the construction of unsymmetrical α-tertiary dialkyl ethers is reported. By merging Lewis acid-mediated ketal activation and visible-light photocatalytic reduction, in situ-generated α-alkoxy radicals were found to engage in addition reactions with a variety of olefinic partners. Good reaction efficiency is demonstrated with a range of ketals of aromatic and aliphatic ketones. Extension to acetal substrates is also described, demonstrating the overall synthetic utility of this methodology for complex ether synthesis.

Detection and identification of acetylcholinesterase inhibitors in Annona cherimola Mill. by effect-directed analysis using thin-layer chromatography-bioassay-mass spectrometry.

Acetylcholinesterase (AChE) inhibitors are considered an important strategy in the treatment of neurological disorders such as Alzheimer's disease. A simple and fast planar chromatography-bioassay methodology has been established to detect bioactive molecules in cherimoya fruit. Detect and identify AChE inhibitors in cherimoya by high-performance thin-layer chromatography (HPTLC)-bioassay-mass spectrometry (MS) and related techniques. Effect-directed analysis by planar chromatography-bioassay-mass spectrometry was applied to detect and identify AChE inhibitors in pulp, peel and cherimoya seed. Bioassay was optimised establishing the following conditions: enzymatic solution (1.0UmL-1 ), 1-naphtyl acetate substrate (1.5mgmL-1 ) and Fast Blue B salt (1.0mgmL-1 ). TLC-MS interface was used to directly elute the active zones into a mass spectrometer or to a micro-vial for further off-line studies. Two AChE inhibitory bands were detected in peel extracts. An analysis via HPTLC-MS and high-performance liquid chromatography diode array detector tandem mass spectrometry (HPLC-DAD-MS/MS) allowed to characterise three potential AChE inhibitors: anonaine (m/z 266 [M+H]+ ; UV λmax = 269.6nm), glaucine (m/z 256 [M+H]+ ; UV λmax = 282.9 and 300.6nm) and xylopine (m/z 296 [M+H]+ ; UV λmax = 278.5nm). The application of this optimised high throughput method allowed to establish the presence of three potential AChE inhibitors in cherimoya peel. For the first time AChE inhibitory capacity of these alkaloids is reported.

Nanocomposite membranes for osmotic processes: Incorporation of functionalized hydroxyapatite in porous substrate and in selective layer

Development of new membrane materials for osmotic processes is an important field for increasing the efficiency of the technology. In this work, hydroxyapatite particles (Hapf) functionalized by plasma treatment were added to a porous cellulose acetate substrate and to a selective polyamide layer of nanocomposite membranes to evaluate its performance in osmotic processes. Contact angle, scanning electron microscopy, FT-IR, zeta potential and atomic force microscopy were performed to characterize nanocomposite membranes. Hapf incorporation in the porous CA substrate improved the water flux in forward osmosis from 13.8 to 18.0 L·h−1·m−2, which was related to the augmented hydrophilicity and lower diffusion resistance of the substrate. The addition of particles in the selective layer allowed a further increase up to 22.6 L·h−1·m−2, without affecting the reverse salt flux. For reverse osmosis, water permeability increased from 0.83 to 1.41 L·h−1·m−2·bar−1, maintaining high rejection for NaCl and MgSO4, when particles were incorporated into the selective layer. Composite membranes with CA porous substrate and PA selective layer exhibited promising properties for forward osmosis, and the incorporation of novel functionalized Hapf in both layers allowed for a further adjustment of the membrane hydrophilicity and indicates an advance in membrane material technology.

Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology

Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(eth-ylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 °C and subsequent cooling, whereby aflat substrate was achieved by compression at 72 °C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads, optical storage, or cell instructive substrates.

PVA/TEOS crosslinked membranes incorporating zinc oxide nanoparticles and sodium alginate to improve reverse osmosis performance for desalination

ABSTRACTPure water is becoming less available with increases in world population, so seawater desalination is becoming more important. For efficient seawater desalination, this paper proposes a novel mixed matrix membrane (MMM) based on the deposition of a poly(vinyl alcohol) (PVA) nanofibrous active layer on a 3‐triethoxysilylpropylamine‐functionalized cellulose acetate substrate. The active layer is fabricated by utilizing a tetraethyl orthosilicate–crosslinked PVA incorporating zinc oxide nanoparticles (ZnO‐NPs) and sodium alginate (NaAlg). The overall reverse osmosis performance of the MMMs is enhanced by the infusion of ZnO‐NPs and NaAlg in PVA; we find the optimum concentration for the best performance to be ZnO‐NPs at 0.1 wt % and NaAlg at 0.01 wt %. In terms of permeation flux, salt rejection, salt passage, stability, long‐term rejection, membrane antifouling, reusability, and chlorine resistance, the proposed MMMs are examined using a dead‐end reverse osmosis filtration setup. The results show that the active layer achieves an optimal permeation flux of 34.6 L/m2 h, a natural sea salt rejection of 97%, and a chlorine resistance of 93%, suggesting that the proposed MMMs can be useful for seawater desalination. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47559.

Enol Acetates: Versatile Substrates for the Enantioselective Intermolecular Tsuji Allylation.

A highly versatile enantioselective intermolecular Tsuji allylation that generates alpha-quaternary stereocenters is reported. The methodology utilizes a prochiral enol acetate as a substrate, which is the last class of the original Tsuji substrates to be successfully employed in an enantioselective variant of the venerable reaction. This development enables a highly convergent approach that lends itself to rapid diversification and analogue synthesis by facilitating the incorporation of the allyl moiety from an allylic alkoxide, obviating the need for the preparation of allylic enol carbonates. The reaction is operationally simple and employs the readily available PHOX ligand class. More than 30 examples are reported that proceed with enantiomeric excess (ee) values of up to 96% and a scope that tolerates a wide range of functional groups on the allylic component. The enol acetate substrates are readily prepared from both aryl and aliphatic ketones, where the regioselective preparation has long been known utilizing a variety of methods. The power of this methodology lies in its ability to quickly produce a diverse set of single enantiomer products using different allylic alcohols with a common prochiral enol acetate. This is demonstrated here by two rapid formal syntheses of hamigeran B that utilize a common intermediate to intercept both Clive and Stoltz intermediates, and also to prepare novel intermediate analogues.

Iridium-Catalyzed Enantioselective and Diastereoselective Allylation of Dioxindoles: A One-Step Synthesis of 3-Allyl-3-hydroxyoxindoles.

An iridium-catalyzed asymmetric allylation of dioxindoles, 3-hydroxyoxindoles, regulated by prosthetic groups has been accomplished under mild conditions. The methodology is applicable to a diverse array of 3-hydroxyoxindole and cinnamyl acetate substrates. A range of 3-allyl-3-hydroxyoxindoles containing vicinal tetrasubstituted and trisubstituted stereocenters can be efficiently synthesized in one-step with excellent enantioselectivity (up to >99% enaniomeric excess (ee)) and good diastereoselectivity (up to 11:1 diastereomeric ratio (dr)).

Self-assembled Cu doped CdS nanostructures on flexible cellulose acetate substrates using low cost sol–gel route

Copper doped Cadmium sulfide (CdS) nanostructures were assembled on flexible cellulose acetate substrates using low cost sol–gel route. The effects of doping concentrations of copper (Cu) on the CdS nanostructures were studied. The sol was prepared in ultrasonic environment and used for the growth of films using spin coater. The particles and films were characterized by structural, morphological, elemental, optical and electrical studies. Micrographs obtained by field emission scanning electron microscopy (FESEM) reveal the rod shape formation in the presence of Cu with increasing doping concentrations Williamson Hall plots obtained using x ray diffraction (XRD) studies indicate the presence of stress in the lattice due to copper doping. The reduction in crystallite size is observed from 7.29 nm to 5.66 nm. Current–voltage curves exhibit ohmic behavior with an appreciable increase in the conductivity with increasing Cu doping concentrations. Samples show excellent photoluminescence behavior with good absorption spectra in the visible region.

The Role of Acetylcholine Esterase in Resistance Mechanism of Plutella xylostella to Emamektin Benzoate

One of the resistance mechanism of P. xylostellato emamektin benzoate is target insensitivity which is acetylcholine esterase that responsible for resistance occurrence. The objective of this study was to determine the role of acetylcholinesterase in the resistance mechanism of P. xylostella population to emamektin benzoate. For enzyme activity analysis, larvae homogenate of the third instar of P. xylostella was prepared. The number of insects required for each scour is 1 for each field population. The protein content in P. xylostella homogenate was measured by the Folin-Ciocalteu test. Non-specific esterase activity with an absorption rate was read using ELISA reader tool with λ = 450 nm. The inhibition level of acetylcholinesterase activity by emamectin benzoate in the tested population was 36.84%. The highest inhibition occurs in Puasan (Ngablak) population. The result shows that a α-naphthyl acetate substrate was used so that it was recorded as non-specific esterase activity and did not exhibit esterase activity which specifically describes emamectin benzoate. Non-specific esterase enzyme activity of either α or β-naphthyl acetate substances to benzoic emamectin in the tested population most of the population was still susceptible. On α-naphthyl acetate substrate, the highest absorbance value found in susceptible population to benzoate emamectin (0.773), while the lowest found in Babrik (Ngablak) population (0.083).

Ex Situ Culturing Experiments Revealed Psychrophilic Hydrogentrophic Methanogenesis Being the Potential Dominant Methane-Producing Pathway in Subglacial Sediment in Larsemann Hills, Antarctic.

It was recognized only recently that subglacial ecosystems support considerable methanogenic activity, thus significantly contributing the global methane production. However, only limited knowledge is available on the physiological characteristics of this kind of methanogenic community because of the technical constraints associated with sampling and cultivation under corresponding environmental conditions. To elucidate methanogenesis beneath the glacial margin in East Antarctic Ice Sheet, we took an integrated approach that included cultivation of microbes associated with the sediment samples in the lab and analysis of mcrA gene therein. After 7 months of incubation, the highest rate of methanogenesis [398 (pmol/day)/gram] was observed at 1°C on a supply of H2. The rates of methanogenesis were lower on acetate or unamended substrate than on H2. The rates on these two substrates increased when the temperature was raised. Methanomicrobiales predominated before and after prolonged incubation, regardless whether H2, acetate, or unamended substrate were the energy source. Therefore, it was inferred that psychrophilic hydrogenotrophic methanogenesis was the primary methane-producing pathway in the subglacial ecosystem we sampled. These findings highlight the effects of temperature and substrate on potential methanogenesis in the subglacial sediment of this area, and may help us for a better estimation on the Antarctica methane production in a changing climate.

Insight into catalytic reduction of CO2 to methane with silanes using Brookhart's cationic Ir(iii) pincer complex.

Using density functional theory computations, we investigated in detail the underlying reaction mechanism and crucial intermediates present during the reduction of carbon dioxide to methane with silanes, catalyzed by the cationic Ir-pincer complex ((POCOP)Ir(H)(acetone)+, POCOP = 2,6-bis(dibutylphosphinito)phenyl). Our study postulates a plausible catalytic cycle, which involves four stages, by sequentially transferring silane hydrogen to the CO2 molecule to give silylformate, bis(silyl)acetal, methoxysilane and the final product, methane. The first stage of reducing carbon dioxide to silylformate is the rate-determining step in the overall conversion, which occurs via the direct dissociation of the silane Si–H bond to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O bond of a weakly coordinated Ir–CO2 moiety, with a free energy barrier of 29.5 kcal mol−1. The ionic SN2 outer-sphere pathway in which the CO2 molecule nucleophilically attacks at the η1-silane iridium complex to cleave the η1-Si–H bond, followed by the hydride transferring from iridium dihydride [(POCOP)IrH2] to the cation [OC–OSiMe3]+, is a slightly less favorable pathway, with a free energy barrier of 33.0 kcal mol−1 in solvent. The subsequent three reducing steps follow similar pathways: the ionic SN2 outer-sphere process with silylformate, bis(silyl)acetal and methoxysilane substrates nucleophilically attacking the η1-silane iridium complex to give the ion pairs [(POCOP)IrH2] [HC(OSiMe3)2]+, [(POCOP)IrH2] [CH2(OSiMe3)2(SiMe3)]+, and [(POCOP)IrH2] [CH3O(SiMe3)2]+, respectively, followed by the hydride transfer process. The rate-limiting steps of the three reducing stages are calculated to possess free energy barriers of 12.2, 16.4 and 22.9 kcal mol−1, respectively. Furthermore, our study indicates that the natural iridium dihydride [(POCOP)IrH2] generated along the ionic SN2 outer-sphere pathway could greatly facilitate the silylation of CO2, with a potential energy barrier calculated at a low value of 16.7 kcal mol−1.