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Formaldehyde is one of the most common indoor air pollutants that seriously damage human health. It is of significant importance to effectively remove indoor formaldehyde. In this work, a novel cement-based composite with ZIF-8@TiO2-coated activated carbon fibers (TiO2-ACFs) was prepared and shown to remove the indoor formaldehyde effectively. TiO2 was coated on ACFs via atomic layer deposition, and then ZIF-8 was grown on the surface of TiO2-ACFs. The ZIF-8@TiO2-ACFs were then mixed with cement slurry and thus formed a cement-based composite, which exhibited excellent formaldehyde removal performance. In particular, if assisted with UV light, the removal efficiency for formaldehyde by the cement-based composite showed an obvious increase.

Cocrystallization is an important method to obtain high-energy and low-sensitivity explosives. Therefore, the synthesis, structures, and properties of cocrystal energetic materials have become a highly active research topic. Studying the physical and chemical properties of cocrystal energetic materials by molecular dynamics is of great significance for the in-depth understanding and design/synthesis of new cocrystal energetic materials. This review introduces the method of molecular dynamics, the cocrystal energetic materials synthesized successfully to date, and the application of molecular dynamics to cocrystal energetic materials. The existing problems and future development directions are discussed. We hope that this review will encourage researchers interested in the field to design and synthesize high-energy and low-sensitive energetic materials with practical application value.

Density functional theory (DFT) is employed to investigate the promotion of B(C6F5)3 as a ligand for titanium (or vanadium) catalysts in ethylene/1-hexene copolymerization reactions. The results reveal that (I) Ethylene insertion into TiB (with B(C6F5)3 as a ligand) is preferred over TiH, both thermodynamically and kinetically. (II) In TiH and TiB catalysts, the 2,1 insertion reaction (TiH21 and TiB21) is the primary pathway for 1-hexene insertion. Furthermore, the 1-hexene insertion reaction for TiB21 is favored over TiH21 and is easier to perform. Consequently, the entire ethylene and 1-hexene insertion reaction proceeds smoothly using the TiB catalyst to yield the final product. (III) Analogous to the Ti catalyst case, VB (with B(C6F5)3 as a ligand) is preferred over VH for the entire ethylene/1-hexene copolymerization reaction. Moreover, VB exhibits higher reaction activity than TiB, thus agreeing with experimental results. Additionally, the electron localization function and global reactivity index analysis indicate that titanium (or vanadium) catalysts with B(C6F5)3 as a ligand exhibit higher reactivity. Investigating the promotion of B(C6F5)3 as a ligand for titanium (or vanadium) catalysts in ethylene/1-hexene copolymerization reactions will aid in designing novel catalysts and lead to more cost-effective polymerization production methods. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate the three-component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) using N-heterocyclic carbene silver as the catalyst. This study reveals that the addition reaction between the catalyst N-heterocyclic carbene silver and phenylacetylene (PAE) forms Ag_PAE. Subsequently, one hydrogen atom of the Ag_PAE migrates to the nitrogen atom of the Amine. Thereafter, the amine aldehyde condensation reaction generates a molecule of water and an imine ion with (Path one) or without (Path two) another amine catalyst. Path one has a lower reaction barrier than Path two. Subsequently, the imine ion reacts with silver phenylacetylide to generate the A3 coupling reaction product propargylamine (PPA). Furthermore, the triple bond and −N3 group in PPA undergo a cycloaddition reaction and generate the final product (PR). The entire reaction is strongly exothermic, and, therefore, the reaction is easy to conduct. Moreover, conceptual density functional theory calculations confirm the reaction mechanism. Investigating the mechanism of these reactions will be helpful for understanding and developing new synthesis strategies for similar functional compounds. [ABSTRACT FROM AUTHOR]

High-energy low-sensitivity explosives are research objectives in the field of energetic materials, and the formation of cocrystals is an important method to improve the safety of explosives. However, the sensitivity reduction mechanism of cocrystal explosives is still unclear. In this study, CL-20/TNT, CL-20 and TNT crystals were taken as research objects. On the basis of the ReaxFF-lg reactive force field, the propagation process of the wave front in the crystals at different impact velocities was simulated. The molecular dynamics data were used to analyze the molecular structure changes and initial chemical reactions, and to explore the sensitivity reduction mechanism of the CL-20/TNT cocrystal. The results showed that the chemical reaction of the CL-20/TNT cocrystal, compared with the CL-20 single crystal, is different under different impact velocities. At an impact velocity of 2 km/s, polymerization and separation of the component molecules weakened the decomposition of CL-20. At an impact velocity of 3 km/s, the decay rates of CL-20 and TNT in the cocrystal decreased, and the intermediate products were enhanced, such as nitrogen oxides. At an impact velocity of 4 km/s, the cocrystal had little effect on the decay rates of the molecules and formation of CO2, but it enhanced formation of N2 and H2O. This may explain the reason for the impact-sensitivity reduction of the CL-20/TNT cocrystal. [ABSTRACT FROM AUTHOR]

For a theoretical model study on the cyclic reaction of 4-hydroxybutanal (4-OH-BL), we have examined five assumed reaction pathways (I-V) by performing the B3LYP calculations in the gas phase and self-consistent isodensity polarized continuum model (SCIPCM)-B3LYP calculations in aqueous solution. Pathways II (4-OH-BL + [H.sup.+]), III (4-OH-BL + [H.sub.3][O.sup.+]), and IV (4-OH-BL + [H.sub.3][O.sup.+] + [H.sub.2]O) represent three models for the cyclic reaction catalyzed by Bronsted acids. The present study leads to the following conclusions concerning the five pathways (mainly on the basis of the calculation results in the solution). The high barrier along pathway I (with no catalyst) implies that the reaction does not occur without a catalyst, and the extremely large stabilization energy of the intermediate implies that pathway II is not a realistic model for the reaction catalyzed by Bronsted acid. Along pathway III, there are two intermediates and a transition state in between, and they are 10-16 kcal/mol lower in energy than the reactants (4-OH-BL + [H.sub.3][O.sup.+]). Along pathway IV, there is only one intermediate, and it is 20.6 kcal/mol lower in energy than the reactants (4-OH-BL + [H.sub.3][O.sup.+] + [H.sub.2]O). Pathways III and IV are predicted to be feasible. Energetically, pathway IV is more favourable than pathway III and it is considered as a rational model for the cyclic reaction of 4-OH-BL catalyzed by Bronsted acid. Our calculations for pathway V (catalyzed by [H.sub.2]O) indicate that the water molecule may also serve as a catalyst for the cyclic reaction. The transition state along pathway V is 20.0 kcal/mol higher in energy than the reactants (4-OH-BL + [H.sub.2]O), and one can clearly see the 'proton wire' in its structure. Our calculations show strong solvent effects on energetics of the charged intermediates along pathways II, III, and IV. Key words: cyclic reaction of 4-hydroxybutanal, catalyzed by Bronsted acid, B3LYP, self-consistent isodensity polarized continuum model (SCIPCM), model study. Comme modele theorique pour une etude de la reaction cyclique du 4-hydroxybutanal (4-OH-BL), on a etudie cinq presumees voies reactionnelles (I-V) en effectuant des calculs B3LYP en phase gazeuse et des calculs SCIPCM-B3LYP en solution et les voies reactionnelles II (4-OH-BL + [H.sup.+]), III (4-OH-BL + [H.sub.3][O.sup.+]) et IV (4-OH-BL + [H.sub.3][O.sup.+] + [H.sub.2]O) representent trois modeles pour la reaction cyclique catalysee par les acides de Bronsted. La presente etude conduit aux conclusions suivantes concernant les cinq voies reactionnelles (principalement sur la base des resultats de calculs en solution). La barriere elevee le long de la voie I (sans catalyseur) implique que la reaction ne se produit pas sans catalyseur et l'energie de stabilisation extremement grande de l'intermediaire implique que la voie reactionnelle II n'est pas un modele realiste pour la reaction catalysee par un acide de Bronsted. Le long de la voie III, on rencontre deux intermediaires et un etat de transition entre les deux et leurs energies sont de 10 a 16 kcal/mol inferieures a celles des reactifs (4-OH-BL + [H.sub.3][O.sup.+]). Le long de la voie IV, il n'existe qu'un intermediaire et son energie est de 20,6 kcal/mol inferieure a l'energie des reactifs (4-OH-BL + [H.sub.3][O.sup.+] + [H.sub.2]O). Les voies reactionnelles III et IV sont donc toutes les deux possibles. D'un point de vue energetique, la voie IV est plus favorable que la voie III et on la considere comme un modele rationnel pour la reaction du 4-OH-BL catalysee par un acide de Bronsted. Les calculs pour la voie V (catalysee par l'eau) indiquent que la molecule d'eau peut aussi servir de catalyseur pour la reaction cyclique. L'energie de transition de l'etat de transition le long de la voie V est de 20,0 kcal/mol plus elevee que celles des reactifs (4-OH-BL + [H.sub.2]O) et on peut voir le << treillis de proton >> dans sa structure. Les calculs montrent l'existence d'importants effets de solvant sur les energies des intermediaires charges le long des voies reactionnelles II, III et IV. Mots-cles : reaction cyclique du 4-hydroxybutanal, catalyse par un acide de Bronsted, B3LYP, SCIPCM, etude modele. [Traduit par la Redaction], Introduction Nucleophilic reactions are very important reactions in organic chemistry. (1) There are numerous theoretical studies (2-9) on nucleophilic substitution reactions ([S.sub.N]2 reactions), but less theoretical studies on nucleophilic addition [...]

Density functional theory has been used to elucidate the mechanism of Pd copolymerization of cyclopropenone with ethylene. The results reveal that introducing ethylene and cyclopropenone to Pd catalyst is thermodynamically feasible and generates the α,β-unsaturated ketone unit (UnitA). Cis-mode insertion and Path A1a are the most favorable reaction routes for ethylene and cyclopropenone, respectively. Moreover, cyclopropenone decomposition can generate CO in situ without a catalyst or with a Pd catalyst. The Pd-catalyzed decomposition of cyclopropenone exhibits a lower reaction barrier (22.7 kcal/mol) than its direct decomposition. Our study demonstrates that incorporating CO into the Pd catalyst can generate the isolated ketone unit (UnitB). CO is formed first; thereafter, UnitB is generated. Therefore, the total energy barrier of UnitB generation, accounting for the CO barrier, is 22.7 kcal/mol, which is slightly lower than that of UnitA generation (24.0 kcal/mol). Additionally, the possibility of copolymerizing ethylene, cyclopropenone, and allyl acetate (AAc) has been investigated. The free energy and global reactivity index analyses indicate that the cyclopropenone introduction reaction is more favorable than the AAc insertion, which is consistent with the experimental results. Investigating the copolymerization mechanism will help to develop of a functionalization strategy for polyethylene polymers. [ABSTRACT FROM AUTHOR]

The electronic structure of s-cis-1,3-butadiene (CH2=CH–CH=CH2) encouraged us to explore a transition metal (TM) free strategy for homolytic H2 activation by replacing both terminal CH2 groups of CH2=CH–CH=CH2 with X = NH, O, SiH2, PH, S, GeH2, AsH, and Se. The study predicts that the six molecules with X = SiH2, PH, S, GeH2, AsH, and Se may activate H2 with barriers lower than 21.7 kcal mol−1, but the three with X = CH2, NH, and O have barriers higher than 38.9 kcal mol−1. Unlike homolytic H2 activation by TM complexes, which occurs on an active site with only one reactive center, the present activations are enabled through an active site with two reactive centers. The greatly increased reactivity of these heavier analogs originates from the significantly reduced EOFMO–EUFMO gaps (EOFMO/EUFMO represents the occupied/unoccupied frontier molecular orbital that has the correct symmetry to interact with the H2σ*/σ orbital). Interestingly, H2 activations by experimentally reported derivatives with X = PH, S, and Se were predicted to have experimentally accessible barriers and to be exergonic, which is an exciting observation. The electronic structure of 1,3-dipoles is also suitable for designing geminal active sites for homolytic H2 activation. [ABSTRACT FROM AUTHOR]

The mechanistic details of nickel-catalyzed reduction of CO(2) with catecholborane (HBcat) have been studied by DFT calculations. The nickel pincer hydride complex ({2,6-C(6)H(3)(OP(t)Bu(2))(2)}NiH = [Ni]H) has been shown to catalyze the sequential reduction from CO(2) to HCOOBcat, then to CH(2)O, and finally to CH(3)OBcat. Each process is accomplished by a two-step sequence at the nickel center: the insertion of a C═O bond into [Ni]H, followed by the reaction of the insertion product with HBcat. Calculations have predicted the difficulties of observing the possible intermediates such as [Ni]OCH(2)OBcat, [Ni]OBcat, and [Ni]OCH(3), based on the low kinetic barriers and favorable thermodynamics for the decomposition of [Ni]OCH(2)OBcat, as well as the reactions of [Ni]OBcat and [Ni]OCH(3) with HBcat. Compared to the uncatalyzed reactions of HBcat with CO(2), HCOOBcat, and CH(2)O, the nickel hydride catalyst accelerates the H(δ-) transfer by lowering the barriers by 30.1, 12.4, and 19.6 kcal/mol, respectively. In general, the catalytic role of the nickel hydride is similar to that of N-heterocyclic carbene (NHC) catalyst in the hydrosilylation of CO(2). However, the H(δ-) transfer mechanisms used by the two catalysts are completely different. The H(δ-) transfer catalyzed by [Ni]H can be described as hydrogen being shuttled from HBcat to nickel center and then to the C═O bond, and the catalyst changes its integrity during catalysis. In contrast, the NHC catalyst simply exerts an electronic influence to activate either the silane or CO(2), and the integrity of the catalyst remains intact throughout the catalytic cycle. The comparison between [Ni]H and Cp(2)Zr(H)Cl in the stoichiometric reduction of CO(2) has suggested that ligand sterics and metal electronic properties play critical roles in controlling the outcome of the reaction. A bridging methylene diolate complex has been previously observed in the zirconium system, whereas the analogous [Ni]OCH(2)O[Ni] is not a viable intermediate, both kinetically and thermodynamically. Replacing HBcat with PhSiH(3) in the nickel-catalyzed reduction of CO(2) results in a high kinetic barrier for the reaction of [Ni]OOCH with PhSiH(3). Switching silanes to HBcat in NHC-catalyzed reduction of CO(2) generates a very stable NHC adduct of HCOOBcat, which makes the release of NHC less favorable.

This study extends our previous work of using π-FLP strategy to develop metal-free hydrogenation catalysts. Using small MeN=CMe(2) imine (im1) as a model, we previously designed cat1 and cat2 catalysts. But it is unclear whether they are capable of catalyzing the hydrogenations of bulky imines. Using tBuN=C(H)Ph (im2) as a representative of large imines, we assessed the energetics of the cat1- and cat2-catalyzed im2 hydrogenations. The predicted energetics indicates that they can still catalyze large imine hydrogenations with experimentally accessible kinetic barriers, although the energetics becomes less favorable. To improve the catalysis, we proposed new catalysts (cat3 and cat4) by tailoring cat1 and cat2. The study indicates that cat3 and cat4 could have better performance for the hydrogenation of the bulky im2 than cat1 and cat2. Remarkably, cat3 and cat4 are also found suitable for small imine (im1) hydrogenation. Examining the hydrogen transfer substeps in the eight hydrogenations involved in this study, we observed that the mechanism for the hydrogen transfer step in the catalytic cycles depends on the steric effect between catalyst and substrate. The mechanism can be switched from stepwise one in the case of large steric effect (e.g.im2/cat2) to the concerted one in the case of small steric effect (e.g.im1/cat3). The new catalysts could be better targets for experimental realization because of their simpler constructions.