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Journal articleShankar R, Marchesini S, Petit C, 2018,
Enhanced Hydrolytic Stability of Porous Boron Nitride via the Control of Crystallinity, Porosity and Chemical Composition
<jats:p>Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or a controlled stability) over a range of chemical environments, and particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical-chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample exhibits enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures, and will progress the implementation of the material in applications involving interfacial phenomena.</jats:p><jats:p />
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Journal articleDias E, Christoforidis K, Francas L, et al., 2018,
Tuning thermally treated graphitic carbon nitride for H₂ evolution and CO₂ photoreduction: The effects of material properties and mid-gap states
, ACS Applied Energy Materials, Vol: 1, Pages: 6524-6534, ISSN: 2574-0962Graphitic carbon nitride (g-C3N4) is regarded as an attractive photocatalyst for solar fuel production, i.e., H2 evolution and CO2 photoreduction. Yet, its structural, chemical and optoelectronic properties are very much dependent on the synthesis method and are likely to contribute differently whether H2 evolution or CO2 reduction is considered. Little is known about this aspect making it difficult to tailor g-C3N4 structure and chemistry for a specific photoreaction. Herein, we create g-C3N4 of varying chemical, structural and optical features by applying specific thermal treatments and investigating the effects of the materials properties on solar fuel production. The samples were characterized across scales using spectroscopic, analytical and imaging tools, with particular attention given to the analyses of trap states. In the case of H2 evolution, the reaction is controlled by light absorption and charge separation enabled by the presence of trap states created by N vacancies. In the case of CO2 photoreduction, reactant adsorption appears as a dominating factor. The analyses also suggest that the thermal treatment leads to the formation of trap states located close to the valence band of g-C3N4.
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Journal articlePapoulis D, Panagiotaras D, Tsigrou P, et al., 2018,
Halloysite and sepiolite -TiO2 nanocomposites: Synthesis characterization and photocatalytic activity in three aquatic wastes
, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, Vol: 85, Pages: 1-8, ISSN: 1369-8001 -
Journal articleStafford JP, Patapas A, Uzo N, et al., 2018,
Towards scale‐up of graphene production via nonoxidizing liquid exfoliation methods
, AIChE Journal, Vol: 64, Pages: 3246-3276, ISSN: 0001-1541Graphene, the two‐dimensional form of carbon, has received a great deal of attention across academia and industry due to its extraordinary electrical, mechanical, thermal, chemical, and optical properties. In view of the potential impact of graphene on numerous and diverse applications in electronics, novel materials, energy, transport, and healthcare, large‐scale graphene production is a challenge that must be addressed. In the past decade, top–down production has demonstrated high potential for scale‐up. This review features the recent progress made in top–down production methods that have been proposed for the manufacturing of graphene‐based products. Fabrication methods such as liquid‐phase mechanical, chemical and electrochemical exfoliation of graphite are outlined, with a particular focus on nonoxidizing routes for graphene production. Analysis of exfoliation mechanisms, solvent considerations, key advantages and issues, and important production characteristics including production rate and yield, where applicable, are outlined. Future challenges and opportunities in graphene production are also highlighted.
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Journal articleChristoforidis KC, Syrgiannis Z, La Parola V, et al., 2018,
Metal-free dual-phase full organic carbon nanotubes/g-C3N4 heteroarchitectures for photocatalytic hydrogen production
, NANO ENERGY, Vol: 50, Pages: 468-478, ISSN: 2211-2855 -
Journal articleEvans A, Luebke R, Petit C, 2018,
The use of metal-organic frameworks for CO purification
, Journal of Materials Chemistry A, Vol: 6, Pages: 10570-10594, ISSN: 2050-7496Carbon monoxide (CO) represents a key feedstock in the petrochemical industry and must be produced in sufficient purity for industrial use. Such requirement imposes strict performance targets on separation technologies and processes employed to purify CO. An important consideration, adding further difficulty to this separation, is the chemical complexity of some CO-containing streams which include gas molecules such as H2, CO2, N2, H2O. While processes such as cryogenic distillation and/or absorption can be applied, the associated high-energy consumption and/or poor stability of the absorption solvents remain key barriers and considerations in large-scale deployment. In this review, we provide an up-to-date account of the literature on adsorption technologies for CO purification with particular emphasis on the use of metal–organic frameworks (MOFs). We highlight key chemical and structural features of MOFs which govern the adsorption mechanisms as well as the resulting performance metrics (e.g. uptake and selectivity). We discuss important aspects of technology scale-up including sorbent robustness, manufacturability and performance under ‘real’ conditions. A comparison of literature reported adsorbents, tested for CO adsorption, including a benchmark material is provided. Based on our analysis of the field, we present an outlook of future challenges as well as opportunities for future research in this area.
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Journal articlePetit C, 2018,
Present and future of MOF research in the field of adsorption and molecular separation.
, Current Opinion in Chemical Engineering, Vol: 20, Pages: 132-142, ISSN: 2211-3398It is a critical and exciting time for research on adsorption using metal–organic frameworks (MOFs) as we witness the commercial release of the MOF-based products TruPick and ION-X, two MOF-based products with application in the food packaging and electronic gas delivery platform sectors, respectively. Such milestones call for reflection on the outputs of MOF research in the field of adsorption so far and the challenges and opportunities lying ahead. To this end, this review provides a snapshot of current trends in this research space (i.e. new adsorption application, manufacturing, role of modeling), highlights the most promising structures for given applications (i.e. in gas adsorption, gas storage, molecular separation, water purification and harvesting), points to technical barriers, and exposes a vision for future research in this area.
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Journal articleHerdes C, Petit C, Mejia A, et al., 2018,
Combined experimental, theoretical, and molecular simulation approach for the description of the fluid-phase behavior of hydrocarbon mixtures within shale rocks
, Energy and Fuels, Vol: 32, Pages: 5750-5762, ISSN: 0887-0624An experimental, theoretical, and molecular simulation consolidated framework for the efficient characterization of the adsorption and fluid-phase behavior of multi-component hydrocarbon mixtures within tight shale rocks is presented. Fluid molecules are described by means of a top-down coarse-grained model where simple Mie intermolecular potentials are parametrized by means of the statistical associating fluid theory. A four-component (methane, pentane, decane, naphthalene) mixture is used as a surrogate model with a composition representative of commonly encountered shale oils. Shales are modeled as a hierarchical network of nanoporous slits in contact with a mesoporous region. The rock model is informed by the characterization of four distinct and representative shale core samples through nitrogen adsorption, thermogravimetric analysis, and contact angle measurements. Experimental results suggest the consideration of two types of pore surfaces: a carbonaceous wall representing the kerogen regions of a shale rock, and an oxygenated wall representing the clay-based porosity. Molecular dynamics simulations are performed at constant overall compositions at a temperature of 398.15 K (257 °F) and explore pressures from 6.9 MPa up to 69 MPa (1000–10000 psi). Simulations reveal that it is the organic nanopores of 1 and 2 nm that preferentially adsorb the heavier components, while the oxygenated counterparts show little selectivity between the adsorbed and free fluid. Upon desorption, this trend is intensified, as the fluid phase in equilibrium with a carbon nanopore becomes increasing leaner (richer in light components) and almost completely depleted of the heavy components which remain trapped in the nanopores and surfaces of the mesopores. Oxygenated pores do not contribute to this unusual behavior, even for the very tight pores considered. The results presented elucidate the relative importance of considering both the pore size distribution and the heterogen
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Journal articleBui M, Adjiman CS, Bardow A, et al., 2018,
Carbon capture and storage (CCS): the way forward
, Energy and Environmental Science, Vol: 11, Pages: 1062-1176, ISSN: 1754-5692Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.
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Journal articleMarchesini S, McGilvery CM, Bailey J, et al., 2017,
Template-free synthesis of highly porous boron nitride: insights into pore network design and impact on gas sorption
, ACS Nano, Vol: 11, Pages: 10003-10011, ISSN: 1936-0851Production of biocompatible and stable porous materials, e.g., boron nitride, exhibiting tunable and enhanced porosity is a prerequisite if they are to be employed to address challenges such as drug delivery, molecular separations, or catalysis. However, there is currently very limited understanding of the formation mechanisms of porous boron nitride and the parameters controlling its porosity, which ultimately prevents exploiting the material’s full potential. Herein, we produce boron nitride with high and tunable surface area and micro/mesoporosity via a facile template-free method using multiple readily available N-containing precursors with different thermal decomposition patterns. The gases are gradually released, creating hierarchical pores, high surface areas (>1900 m2/g), and micropore volumes. We use 3D tomography techniques to reconstruct the pore structure, allowing direct visualization of the mesopore network. Additional imaging and analytical tools are employed to characterize the materials from the micro- down to the nanoscale. The CO2 uptake of the materials rivals or surpasses those of commercial benchmarks or other boron nitride materials reported to date (up to 4 times higher), even after pelletizing. Overall, the approach provides a scalable route to porous boron nitride production as well as fundamental insights into the material’s formation, which can be used to design a variety of boron nitride structures.
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Journal articleCrake A, Christoforidis KC, Kafizas A, et al., 2017,
CO2 capture and photocatalytic reduction using bifunctional TiO2/MOF nanocomposites under UV-vis irradiation
, Applied Catalysis B: Environmental, Vol: 210, Pages: 131-140, ISSN: 0926-3373TiO2 nanosheets and metal-organic framework (NH2-UiO-66) were effectively coupled via an in‐situ growth strategy to form bifunctional materials for the combined capture and photocatalytic reduction of CO2 under UV–vis light irradiation. This was done to take advantage of the high CO2 adsorption capacity of the MOF and the photocatalytic properties of pre-formed TiO2 nanosheets in a single material. The prepared materials were thoroughly characterized using a variety of techniques. They were subsequently tested for CO2 adsorption and CO2 photocatalytic reduction using a heterogeneous gas/solid set-up to imitate both CO2 capture and fixation in a single process. The adopted synthesis process allowed the development of a tight interaction between TiO2 and NH2-UiO-66 forming a heterojunction, while maintaining both the high CO2 uptake and porosity of NH2-UiO-66. The nanocomposites were proven durable and significantly more efficient in reducing CO2 to CO than their single components. Photocatalytic activity was greatly affected by the nanocomposites composition with the optimum TiO2 content doubling the CO evolution rate compared with the pure TiO2. The improved photoactivity was assigned to the enhanced abundance of long lived charge carriers, as revealed by transient absorption spectroscopy (TAS). This most likely occurred due to the effective charge transfer via interface. A possible mechanism is discussed on the basis of the combined catalytic, spectroscopic and CO2 adsorption results.
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Journal articleLeeson D, Mac Dowell N, Shah N, et al., 2017,
A Techno-economic analysis and systematic review of carbon capture and storage (CCS) applied to the iron and steel, cement, oil refining and pulp and paper industries, as well as other high purity sources
, International Journal of Greenhouse Gas Control, Vol: 61, Pages: 71-84, ISSN: 1750-5836In order to meet the IPCC recommendation for an 80% cut in CO2 emissions by 2050, industries will be required to drastically reduce their emissions. To meet these targets, technologies such as carbon capture and storage (CCS) must be part of the economic set of decarbonisation options for industry. A systematic review of the literature has been carried out on four of the largest industrial sectors (the iron and steel industry, the cement industry, the petroleum refining industry and the pulp and paper industry) as well as selected high-purity sources of CO2 from other industries to assess the applicability of different CCS technologies. Costing data have been gathered, and for the cement, iron and steel and refining industries, these data are used in a model to project costs per tonne of CO2 avoided over the time period extending from first deployment until 2050. A sensitivity analysis was carried out on the model to assess which variables had the greatest impact on the overall cost of wide-scale CCS deployment for future better targeting of cost reduction measures. The factors found to have the greatest overall impact were the initial cost of CCS at the start of deployment and the start date at which large scale deployment is started, whilst a slower initial deployment rate after the start date also leads to significantly increased costs.
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Journal articleWoodward RT, Jobbe-Duval A, Marchesini S, et al., 2017,
Hypercrosslinked polyHIPEs as precursors to designable, hierarchically porous carbon foams
, Polymer, Vol: 115, Pages: 146-153, ISSN: 0032-3861Hierarchically porous carbon foams were produced by carbonization of hypercrosslinked polymerized high internal phase water-in-styrene/divinylbenzene emulsions (HIPEs). The hypercrosslinking of these poly(ST-co-DVB)HIPEs was achieved using a dimethoxymethane external crosslinker to ‘knit’ together aromatic groups within the polymers using FriedelCrafts alkylation. By varying the amount of divinylbenzene (DVB) in the HIPE templates and subsequent polymers, the BET surface area and micropore volume of the hypercrosslinked analogues can be varied systematically, allowing for the production of carbon foams, or ‘carboHIPEs’, with varied surface areas, micropore volumes and pore-size distributions. The carboHIPEs retain the emulsion-templated macropores of the original polyHIPE, display excellent electrical conductivities and have surface areas of up to 417 m2/g, all the while eliminating the need for inorganic templates. The use of emulsion templates allows for pourable, mouldable precursors to designable carbonaceous materials.
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Journal articleMarchesini S, Regoutz A, Payne D, et al., 2017,
Tunable porous boron nitride: Investigating its formation and its application for gas adsorption
, Microporous and Mesoporous Materials, Vol: 243, Pages: 154-163, ISSN: 1873-3093Boron nitride (BN) has applications in a number of areas: it can be used as lubricant, as insulating thermoconductive filler or UV-light emitter. BN can also capture large amounts of hydrocarbons and gaseous molecules, provided that it exhibits a porous structure. This porous structure also enables its application as a drug-delivery nanocarrier. Little if anything is known on controlling the porosity of BN, even though it has tremendous implications in terms of adsorption performance and drug delivery properties. To address this aspect, we provide for the first time an in-depth investigation of the effects of the synthesis conditions on the formation of porous BN. The material was also tested for CO2 capture. We found that the intermediate preparation is of paramount importance and can in fact be used to tune the porosity of BN. Owing to a combination of spectroscopic and thermal analyses, we attributed this phenomenon to the variation of the thermal decomposition pattern of the intermediates. The most microporous BN produced was able to capture CO2 while not retaining N2. Overall, this study opens the route for the design of well-controlled porous BN structures to be applied as adsorbents and drug-delivery carriers.
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Journal articleSmit B, Graham R, Styring P, et al., 2016,
CCS - A technology for the future: general discussion
, Faraday Discussions, Vol: 192, Pages: 303-335, ISSN: 1359-6640 -
Conference paperDias E, Petit C, 2016,
Investigation of the Use of Metal-Organic Frameworks for Combined Water Purification and Catalytic H2 Production
, AIChE Fall meeting 2016 -
Journal articleDias EM, Petit C, 2016,
Correction: towards the use of metal–organic frameworks for water reuse: a review of the recent advances in the field of organic pollutants removal and degradation and the next steps in the field
, Journal of Materials Chemistry A, Vol: 4, Pages: 3565-3565, ISSN: 2050-7496 -
Journal articleHong J, Chen C, Bedoya FE, et al., 2016,
Carbon nitride nanosheet/metal–organic framework nanocomposites with synergistic photocatalytic activities
, Catalysis Science & Technology, Vol: 6, Pages: 5042-5051, ISSN: 2044-4753Heterogeneous photocatalysis plays a key role in the implementation of novel sustainable technologies, e.g. CO2 conversion into fuel, H2 production from water or organics degradation. The progress of photocatalysis relies on the development of tuneable photocatalysts and particularly the ability to build nanocomposites exhibiting synergistic properties with reduced electron–hole recombination rates. We report for the first time the in situ synthesis of nanocomposites of carbon nitride nanosheets (CNNSs) and metal–organic frameworks (MOFs) for application as photocatalysts. This approach leads to the ‘nano-scale mixing’ of the components, thereby enabling a greater performance compared to other types of 2D materials/MOF composites typically obtained via physical mixing. The objective is to take advantage of the complementary features of the materials while forming a heterojunction. The structural, chemical, photophysical and electrochemical properties of the nanocomposites are characterized and compared to those of the parent materials and their physical mixture. The nanocomposites retain the high specific surface area and strong visible light absorbance of MIL-100(Fe). The intimate contact between the CNNSs and the MOF particles is found to promote the electron–hole separation significantly due to the formation of a heterojunction. Hence, more efficient photocatalytic dye degradation is achieved over the composites than the physical mixture.
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Journal articleCalvez CL, Zouboulaki M, Petit C, et al., 2016,
One step synthesis of MOF–polymer composites
, RSC Adv., Vol: 6, Pages: 17314-17317 -
Journal articleWoodward RT, Fam DWH, Anthony DB, et al., 2016,
Hierarchically porous carbon foams from pickering high internal phase emulsions
, Carbon, Vol: 101, Pages: 253-260, ISSN: 0008-6223Carbon foams were produced from a macroporous poly(divinylbenzene) (poly(DVB) precursor, synthesized by polymerizing the continuous but minority phase of water-in-oil high internal phase emulsions (HIPEs) stabilized by molecular and/or particulate emulsifiers. Both permeable and non-permeable hierarchically porous carbon foams, or ‘carboHIPEs’, were prepared by carbonization of the resulting macroporous polymers at 800 °C. The carbon yields were as high as 26 wt.% of the original polymer. CarboHIPEs retain the pore structure of the macroporous polymer precursor, but with surface areas of up to 505 m2/g and excellent electrical conductivities of 81 S/m. Contrary to some previous reports, the method does not require further modification, such as sulfonation or additional crosslinking of the polyHIPE prior to carbonization, due to the inherently crosslinked structure of poly(DVB). The use of a pourable, aqueous emulsion-template enables simple moulding, minimises waste and avoids the strong acid treatments used to remove many conventional solid-templates. The retention of the macroporous structure is coupled with the introduction of micropores during carbonization, producing hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.
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