Carbon dioxide utilisation technology can contribute to the reduction of atmospheric CO2 levels both through its sequestration from flue gases and indirectly by relieving pressure on conventional feedstocks in chemical manufacturing. A promising approach is to employ CO2 to produce valuable cyclic carbonates (CCs) in reaction with suitable epoxides. This also has the advantage that carbon dioxide replaces toxic and hazardous reactants such as phosgene. In earlier work we have investigated the synthesis of epoxides from cycloalkenes using supported gold and gold–palladium nanoparticles as catalysts and oxygen from air as the oxidant under solvent free conditions. A strong dependence of epoxide selectivity on ring size was observed with C5 < C6 < C7 ≪ C8. In this study we extend this work to the investigation of cycloaddition of CO2 to different cycloalkene oxides with the ultimate aim of designing a process in which both epoxidation of an alkene and incorporation of CO2 could be achieved in a single process. However, we have found the opposite trend for the selectivity to carbonates: smaller ring cycloalkene oxides giving the highest carbonate selectivities while large rings do not yield CCs at all. The product distributions suggest that an alternative ring opening of the epoxides to yield alcohols and ketones is preferred under all the experimental conditions explored for larger ring systems. Additionally, the mechanism of the CC synthesis using a quaternary ammonium salt and ZnBr2 as the catalyst system was investigated using DFT methods. The results of the calculations support the experimental findings.

Cu–ZrO2 catalysts were synthesized by the methanothermal (Me) and oxalate gel precipitation (Og) methods. Detailed characterization of the catalysts synthesized by the Me method shows that these contain only Cu substituted into the tetragonal ZrO2 lattice. For catalysts prepared using the Og method Cu is found not only in the tetragonal ZrO2 lattice but also in the form of CuO particles on the zirconia surface. When these materials were tested for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) it was found that Me materials show no catalytic activity, whereas GVL was formed using Og catalysts. A reduction treatment of the Og catalysts prior to use resulted in a marked increase in the catalytic activity, however, no activity increase was observed when the Me material was exposed to a similar treatment before testing. Based on these results and characterization data, we conclude that the catalytically active component of Cu–ZrO2 catalysts for the hydrogenation of LA is reduced Cu particles dispersed on the catalyst surface with strong interaction with the Cu incorporated zirconia support, while the role of Cu in the zirconia lattice is to improve the adhesion of these particles and maintain their dispersion.

•CO adsorption over Pd nanoparticles modelled by hybrid DFT calculations•Hollow and bridge sites favoured at low CO coverages•Linear, bridge and hollow bound CO co-exist at high coverages.•Simulated and experimental IR spectra of adsorbed CO in excellent agreement•Framework for interpreting experimental CO spectra over Pd catalysts presentedCO vibrational spectra over catalytic nanoparticles under high coverages/pressures are discussed from a DFT perspective. Hybrid B3LYP and PBE DFT calculations of CO chemisorbed over Pd4 and Pd13 nanoclusters, and a 1.1 nm Pd38 nanoparticle, have been performed in order to simulate the corresponding coverage dependent infrared (IR) absorption spectra, and hence provide a quantitative foundation for the interpretation of experimental IR spectra of CO over Pd nanocatalysts. B3LYP simulated IR intensities are used to quantify site occupation numbers through comparison with experimental DRIFTS spectra, allowing an atomistic model of CO surface coverage to be created. DFT adsorption energetics for low CO coverage (θ → 0) suggest the CO binding strength follows the order hollow > bridge > linear, even for dispersion-corrected functionals for sub-nanometre Pd nanoclusters. For a Pd38 nanoparticle, hollow and bridge-bound are energetically similar (hollow ≈ bridge > atop). It is well known that this ordering has not been found at the high coverages used experimentally, wherein atop CO has a much higher population than observed over Pd(111), confirmed by our DRIFTS spectra for Pd nanoparticles supported on a KIT-6 silica, and hence site populations were calculated through a comparison of DFT and spectroscopic data. At high CO coverage (θ = 1), all three adsorbed CO species co-exist on Pd38, and their interdiffusion is thermally feasible at STP. Under such high surface coverages, DFT predicts that bridge-bound CO chains are thermodynamically stable and isoenergetic to an entirely hollow bound Pd/CO system. The Pd38 nanoparticle undergoes a linear (3.5%), isotropic expansion with increasing CO coverage, accompanied by 63 and 30 cm− 1 blue-shifts of hollow and linear bound CO respectively.

Structural properties such as size, shape and density distribution of a range of N-(2-hydroxypropyl)methacrylamide (HPMA) polymers in various solvent models have been investigated. Common atomistic force fields were compared against rotational barriers and relative conformational energies obtained from ab initio and density functional theory (DFT) data for a monomer and dimer of HPMA. This identified the AMBER99 parameter set as the most appropriate for representing the structures and so AMBER99 was employed for all molecular dynamics simulations. MD trajectories were calculated for a range of polymer sizes from 4 to 265 repeat units (2 to 35 kDa). The time averaged radius of gyration was extracted from trajectories and interpreted in the context of Flory's mean field approach. Comparison with data obtained from small angle neutron scattering (SANS) experiments was then used to differentiate between alternative solvent models. The shape adopted by such polymers was evaluated by fitting structures to ellipsoids, to allow separate analysis of radius and density profile along each axis. The density distribution of atoms was defined using these ellipsoids according to centre of mass or centre of neutron scattering lengths, the latter allowing direct comparison with experimental SANS data. We show that computational simulation of such polymers has practical application in obtaining detailed morphological information of polymer solution structure, and as a benchmark for coarse-grained methods.

•We model the adsorption and dissociation of CO on the Fe(111) surface.•Adsorption energies and vibrational frequencies are compared to available literature.•We identify and classify the transition states for CO dissociation.•A low energy pathway to dissociation is found with co-adsorbed C.We present DFT calculations relating to fundamental aspects of the adsorption, molecular diffusion and dissociation pathways available for CO on the Fe(111) surface. On the clean surface CO dissociates most easily from di-bridge (DB) sites with both carbon and oxygen atoms interacting with the surface via a tilted configuration. This adsorption site is 0.52 eV higher in energy than the lowest energy at the shallow hollow site and so CO bond cleavage takes place following molecular migration. The lowest calculated barriers are also found when the molecule re-orientates during the dissociation process to maintain a surface co-ordination for the O atom of at least two.When carbon is pre-adsorbed on the surface we find a small stabilisation of the molecularly adsorbed state when the CO⋯C separation is ~ 3 Å, but repulsive interactions reduce the binding energy at shorter distances. The molecularly adsorbed states are affected by the presence of surface carbon with some structures that are transition states for molecular diffusion becoming minima with co-adsorbed carbon. This also leads to lower energy pathways for CO bond cleavage so that our results indicate that surface carbide formation is auto-catalytic at low C coverage.

Most organic molecules pack in such a way to minimize free space, therefore exhibit minimal void volume and hence permanent porosity in the solid state is rare. We have previously demonstrated the synthesis of porous organic cages that are permanently porous to a variety of gases. However, study of the static structure alone does not adequately explain the porosity of these materials. This is especially evident in CC3, which takes up a large amount of nitrogen experimentally but its porosity is not obvious from consideration of the computed geometric solvent accessible surface area of the static crystal structure obtained from single crystal X-ray diffraction data. In this study, we show that the structure and flexibility of these organic cages is not well represented by “off the shelf” force fields that have been developed in other areas. Hence, we develop and test a bespoke force field (CSFF) for simulating the molecular dynamics of a series of porous organic cage materials. The development of CSFF has unlocked the ability to investigate phenomena that are difficult to study by direct experiments, for example, molecular dynamic analysis of the window diameters in CC3 has helped to rationalize its high N2 uptake. In the future, there is much scope to use CSFF to understand the uptake of gases and also larger guests such as halogens and solvents within a whole host of different cage systems leading on to the use of MD analysis for in silico screening of cage materials for particular molecular separations. If reliable, this could be faster than the associated sorption experiments.

The SIESTA suite of programs allows periodic density functional theory calculations to be carried out on system sizes of several hundred atoms. Here we make use of this to study the interface between Au and MgO surfaces. Atomic Au on MgO(100) shows preferential binding over surface anion sites, while the binding energy at a surface anion vacancy is significantly higher than on the stoichiometric surface. High index surfaces are used to generate kink site structures representative of extended defects and Au adsorption at these sites has a binding energy intermediate between MgO(100) and the anion vacancy. In contrast Au10 clusters are found to bind more strongly to kink sites than anion vacancies. Bader charge analysis demonstrates that electron transfer occurs from the surface to the Au species in all calculations and the distribution of this charge in the Au10 case is discussed.

We apply periodic density functional theory to α-MoO3 and its (010) surface. The formation energy and structure of defects in the form of surface oxygen vacancies are found to depend critically on the treatment of electron localisation which is achieved in the periodic model using the DFT + U method. Calculated vibrational states for the defect free surface are found to agree well with surface science experimental data and we show that the molybdenyl stretching mode is shifted to a lower frequency in the neighbourhood of a terminal oxygen vacancy. Adsorption of molecular oxygen at the defect site can result in O2, O2− or O22− surface species depending on the geometry of adsorption.

Atomistic potential calculations of the relative energies of γ-alumina structures as a function of tetrahedral Al distribution give an exhaustive list of configurations which is used to estimate thermodynamic probabilities, subsequent relaxations allow the influence of configurational entropy on structure to be assessed.

Carbon dioxide utilisation technology can contribute to the reduction of atmospheric CO2 levels both through its sequestration from flue gases and indirectly by relieving pressure on conventional feedstocks in chemical manufacturing. A promising approach is to employ CO2 to produce valuable cyclic carbonates (CCs) in reaction with suitable epoxides. This also has the advantage that carbon dioxide replaces toxic and hazardous reactants such as phosgene. In earlier work we have investigated the synthesis of epoxides from cycloalkenes using supported gold and gold–palladium nanoparticles as catalysts and oxygen from air as the oxidant under solvent free conditions. A strong dependence of epoxide selectivity on ring size was observed with C5 < C6 < C7 ≪ C8. In this study we extend this work to the investigation of cycloaddition of CO2 to different cycloalkene oxides with the ultimate aim of designing a process in which both epoxidation of an alkene and incorporation of CO2 could be achieved in a single process. However, we have found the opposite trend for the selectivity to carbonates: smaller ring cycloalkene oxides giving the highest carbonate selectivities while large rings do not yield CCs at all. The product distributions suggest that an alternative ring opening of the epoxides to yield alcohols and ketones is preferred under all the experimental conditions explored for larger ring systems. Additionally, the mechanism of the CC synthesis using a quaternary ammonium salt and ZnBr2 as the catalyst system was investigated using DFT methods. The results of the calculations support the experimental findings.