Dermot O'Hare

Recent advances in solid sorbents for CO2 capture and new development trends

Carbon dioxide (CO2) capture using solid sorbents has been recognized as a very promising technology that has attracted intense attention from both academic and industrial fields in the last decade. It is astonishing that around 2000 papers have been published from 2011 to 2014 alone, which is less than three years after our first review paper in this journal on solid CO2 sorbents was published. In this short period, much progress has been made and the major research focus has more or less changed. Therefore, we feel that it is necessary to give a timely update on solid CO2 capture materials, although we still have to keep some important literature results published in the past years so as to keep the good continuity. We believe this work will benefit researchers working in both academic and industrial areas. In this paper, we still organize the CO2 sorbents according to their working temperatures by classifying them as such: (1) low-temperature ( 400 °C). Since the sorption capacity, kinetics, recycling stability and cost are important parameters when evaluating a sorbent, these features will be carefully considered and discussed. In addition, due to the huge amounts of cost-effective CO2 sorbents demanded and the importance of waste resources, solid CO2 sorbents prepared from waste resources and their performance are reviewed. Finally, the techno-economic assessments of various CO2 sorbents and technologies in real applications are briefly discussed.

Towards understanding, control and application of layered double hydroxide chemistry

Layered double hydroxides (LDHs) have a vast number of potential applications in fields as diverse as separation chemistry, polymer additives and catalysis. They are facile and cheap to prepare, and are environmentally friendly. In this paper, some of the most exciting recent developments in LDH chemistry are discussed, with an emphasis on how we can control their chemistry and how in situ techniques can provide enhanced understanding of the nanoscopic processes involved in intercalation reactions.

Intercalation and controlled release of pharmaceutically active compounds from a layered double hydroxide.

A series of pharmaceutically active compounds including diclofenac, gemfibrozil, ibuprofen, naproxen, 2-propylpentanoic acid, 4-biphenylacetic acid and tolfenamic acid can be reversibly intercalated into a layered double hydroxide, initial studies suggest that these materials may have application as the basis of a novel tuneable drug delivery system.

Defect‐Rich Ultrathin ZnAl‐Layered Double Hydroxide Nanosheets for Efficient Photoreduction of CO2 to CO with Water

Defect-rich ultrathin ZnAl-layered double hydroxide nanosheets are successfully prepared. Under UV-vis irradiation, these nanosheets are superior efficient catalysts for the photoreduction of CO2 to CO with water. The formed oxygen vacancies lead to the formation of coordinatively unsaturated Zn(+) centers within the nanosheets, responsible for the very high photocatalytic activities.

Flame retardant polymer/layered double hydroxide nanocomposites

Recently, there has been rapid growth in research related to the synthesis and application of flame retardant polymer–layered double hydroxide (LDH) nanocomposites. In order to outline the potential and to promote further developments in the field we have prepared a critical review of the most recent progress in the area. We discuss the techniques and indices (e.g. micro calorimetery, limiting oxygen index, cone calorimetry and UL-94) for evaluating the flame retardant properties. The flame retardant mechanism of LDHs, the types of polymers studied, the effect of LDH chemical composition and the synergistic effect with other fire retardants are reviewed. It is hoped that this review will not only introduce the synthesis, characterisation and application of polymer–LDH nanocomposites for flame retardancy, but also prompt new discussion on the use of LDH dispersions in polymer-based materials.

NiTi-Layered double hydroxides nanosheets as efficient photocatalysts for oxygen evolution from water using visible light

NiTi-Layered double hydroxides (LDH) nanosheets with lateral dimensions in the range 30–60 nm have been prepared using a reverse microemulsion method. These materials exhibit excellent photocatalytic activity (∼2148 μmol g−1 h−1) for oxygen evolution from water using visible light. The quantum yield was found to be 65.0% and 20.0% using monochromatic irradiation at 400 and 650 nm respectively.

High pseudocapacitive cobalt carbonate hydroxide films derived from CoAl layered double hydroxides

A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g(-1) at 5 mA cm(-2)) and higher rate capability and cycling stability (92% maintained after 2000 cycles).

TOF-2: A Large 1D Channel Thorium Organic Framework

A new neutral 1D channel thorium organic framework material (TOF-2) has been synthesized under hydrothermal conditions. TOF-2 exhibits a hexagonal channel structure consisting of eight-coordinate ThO6F2 polyhedra and 1,3,5-benzentricarboxylate ligands. The channels run along the c-axis and are approximately 13 A in diameter. The single-crystal X-ray structure suggests that the amount of void space is 41%. The structure is stable to ca. 400 degrees C. Gas adsorption measurements show deferential gas uptake behavior.

Ring-Opening Polymerization of 19-Electron [2]Cobaltocenophanes: A Route to High-Molecular-Weight, Water-Soluble Polycobaltocenium Polyelectrolytes

Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.

Incorporation of uranium(VI) into metal–organic framework solids, [UO2(C4H4O4)]·H2O, [UO2F(C5H6O4)]·2H2O, and [(UO2)1.5(C8H4O4)2]2[(CH3)2NCOH2]·H2O

Uranium–organic framework solids, in which uranium building units are connected by bidentate dicarboxylate anions such as succinate, glutarate, and isophthalate, were synthesized; the glutarate and isophthalate compounds contain cavities, in which occluded water and organic templates reside.