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Advanced oxidation technologies (AOTs), which involve the in situ generation of highly potent chemical oxidants, such as the hydroxyl radical (áOH), have emerged as an important class of technologies for accelerating the oxidation (and hence removal) of a wide range of organic contaminants in polluted water and air. In this report, standard figures-of-merit are proposed for the comparison and evaluation of these waste treatment technologies. These figures-of-merit are based on electric-energy consumption (for electric-energy-driven systems) or collector area (for solar-energy-driven systems). They fit within two phenomenological kinetic order regimes: 1) for high contaminant concentrations (electric energy per mass, EEM, or collector area per mass, ACM) and 2) for low concentrations (electric energy per order of magnitude, EEO, or collector area per order of magnitude, ACO). Furthermore, a simple understanding of the overall kinetic behavior of organic contaminant removal in a waste stream (i.e., whether zero- or first-order) is shown to be necessary for the description of meaningful electric- or solar-energy efficiencies. These standard figures-of-merit provide a direct link to the electric- or solar-energy efficiency (lower values mean higher efficiency) of an advanced oxidation technology, independent of the nature of the system, and therefore allow for direct comparison of widely disparate AOTs. These figures-of-merit are also shown to be inversely proportional to fundamental efficiency factors, such as the lamp efficiency (for electrical systems), the fraction of the emitted light that is absorbed in the aqueous solution, and the quantum yield of generation of active radicals.

Providing an abundant, clean, and secure renewable energy source is one of the key technological challenges facing mankind. Resurgence in the chemistry and biochemistry of hydrogen, the world's simplest closed-shell molecule, has been spurred by recent scientific and technological interest in hydrogen as an energy carrier and potential transportation fuel. Our current energy infrastructure is dominated by fossil fuel use, which leads to greenhouse gas emissions. Hydrogen is potentially an ideal energy carrier, as it is nonpolluting and gives up both its electrons upon oxidation to form only water. Although it is the most abundant element in the universe, elemental hydrogen is not present in great quantities on earth. A number of key challenges must be overcome for hydrogen to be used broadly in a sustainable future energy infrastructure to solve the globe's energy problems. To accrue the full environmental benefit of hydrogen as an energy carrier, low-carbon intensive, low polluting, and lower cost processes for producing hydrogen from renewable energy sources need to be developed. Scientific advances are needed to develop more energy efficient and cost-effective methods for purification and delivery, to design higher energy density hydrogen storage systems, especially for vehicular on-board storage, and to enable more durable fuel cells for converting hydrogen into electrical energy. Governments and industries, particularly in the United States, Japan, and Europe, have been investing heavily in research and development to overcome the technical barriers for hydrogen production, storage, and utilization to enable a sustainable future energy infrastructure based on hydrogen.

Exploratory synthesis in novel chemical spaces is the essence of solid-state chemistry. However, uncharted chemical spaces can be difficult to navigate, especially when materials synthesis is challenging. Nitrides represent one such space, where stringent synthesis constraints have limited the exploration of this important class of functional materials. Here, we employ a suite of computational materials discovery and informatics tools to construct a large stability map of the inorganic ternary metal nitrides. Our map clusters the ternary nitrides into chemical families with distinct stability and metastability, and highlights hundreds of promising new ternary nitride spaces for experimental investigation-from which we experimentally realized 7 new Zn-and Mg-based ternary nitrides. By extracting the mixed metallicity, ionicity, and covalency of solid-state bonding from the DFTcomputed electron density, we reveal the complex interplay between chemistry, composition, and electronic structure in governing large-scale stability trends in ternary nitride materials.

ContentsGreen Chemistry in the International ContextThe Concept of green ChemistryDefinition of green chemistry | Green chemistry: Why now? | The historical context of green chemistry | The emergence of green chemistryThe Content of Green ChemistryAreas of green chemistry | Preliminary remarks | Alternative feedstocks | Benign reagents/synthetic pathways | Synthetic transformations | Solvents/reaction conditionsGreen Chemistry in the International ContextIt has come to be recognized in recent years, that the science of chemistry is central to addressing the problems facing the environment. Through the utilization of the various subdisciplines of chemistry and the molecular sciences, there is an increasing appreciation that the emerging area of green chemistry1is needed in the design and attainment of sustainable development. A central driving force in this increasing awareness is that green chemistry accomplishes both economic and environmental goals simultaneously through the use of sound, fundamental scientific principles. Recently, a basic strategy has been proposed for implementing the relationships between industry and academia, and hence, funding of the research that constitutes the engine of economic advancement; it is what many schools of economics call the "triple bottom line" philosophy, meaning that an enterprise will be economically sustainable if the objectives of environmental protection, societal benefit, and market advantage are all satisfied2. Triple bottom line is a strong idea for evaluating the success of environmental technologies. It is clear that the best environmentally friendly technology or discovery will not impact on the market if it is not economically advantageous; in the same way, the market that ignores environmental needs and human involvement will not prosper. This is the challenge for the future of the chemical industry, its development being strongly linked to the extent to which environmental and human needs can be reconciled with new ideas in fundamental research. On the other hand, it should be easy to foresee that the success of environmentally friendly reactions, products, and processes will improve competitiveness within the chemical industry. If companies are able to meet the needs of society, people will influence their own governments to foster those industries attempting such environmental initiatives. Of course, fundamental research will play a central role in achieving these worthy objectives. What we call green chemistry may in fact embody some of the most advanced perspectives and opportunities in chemical sciences.It is for these reasons that the International Union of Pure and Applied Chemistry (IUPAC) has a central role to play in advancing and promoting the continuing emergence and impact of green chemistry. When we think about how IUPAC furthers chemistry throughout the world, it is useful to refer to IUPAC's Strategic Plan. This plan demonstrates the direct relevance of the mission of IUPAC to green chemistry, and explains why there is growing enthusiasm for the pursuit of this new area as an appropriate activity of a scientific Union. The IUPAC Strategic Plan outlines among other goals:IUPAC will serve as a scientific, international, nongovernmental body in objectively addressing global issues involving the chemical sciences. Where appropriate, IUPAC will represent the interests of chemistry in governmental and nongovernmental forums.IUPAC will provide tools (e.g., standardized nomenclature and methods) and forums to help advance international research in the chemical sciences.IUPAC will assist chemistry-related industry in its contributions to sustainable development, wealth creation, and improvement in the quality of life.IUPAC will facilitate the development of effective channels of communication in the international chemistry community.IUPAC will promote the service of chemistry to society in both developed and developing countries.IUPAC will utilize its global perspective to contribute toward the enhancement of education in chemistry and to advance the public understanding of chemistry and the scientific method.IUPAC will make special efforts to encourage the career development of young chemists.IUPAC will broaden the geographical base of the Union and ensure that its human capital is drawn from all segments of the world chemistry community.IUPAC will encourage worldwide dissemination of information about the activities of the Union.IUPAC will assure sound management of its resources to provide maximum value for the funds invested in the Union.Through the vehicle of green chemistry, IUPAC can engage and is engaging the international community in issues of global importance to the environment and to industry, through education of young and established scientists, the provision of technical tools, governmental engagement, communication to the public and scientific communities, and the pursuit of sustainable development. By virtue of its status as a leading and internationally representative scientific body, IUPAC is able to collaborate closely in furthering individual national efforts as well as those of multinational entities.An important example of such collaboration in the area of green chemistry is that of IUPAC with the Organization for the Economical Cooperation and Development (OECD) in the project on "Sustainable Chemistry", aimed at promoting increased awareness of the subject in the member countries. During a meeting of the Environment Directorate (Paris, 6 June 1999), it was proposed that United States and Italy co-lead the activity, and that implementation of five recommendations to the member countries be accorded the highest priority, namely:research and developmentawards and recognition for work on sustainable chemistryexchange of technical information related to sustainable chemistryguidance on activities and tools to support sustainable chemistry programssustainable chemistry educationThese recommendations were perceived to have socio-economic implications for worldwide implementation of sustainable chemistry. How IUPAC and, in particular, its Divisions can contribute to this effort is under discussion. IUPAC is recognized for its ability to act as the scientific counterpart to OECD for all recommendations and activities. Although the initiatives being developed by the OECD are aimed primarily at determining the role that national institutions can play in facilitating the implementation and impact of green chemistry, it is recognized that each of these initiatives also has an important scientific component. Whether it is developing criteria or providing technical assessment for awards and recognition, identifying appropriate scientific areas for educational incorporation, or providing scientific insight into the areas of need for fundamental research and development, IUPAC can play and is beginning to play an important role as an international scientific authority on green chemistry.Other multinational organizations including, among others, the United Nations, the European Union, and the Asian Pacific Economic Community, are now beginning to assess the role that they can play in promoting the implementation of green chemistry to meet environmental and economic goals simultaneously. As an alternative to the traditional regulatory framework often implemented as a unilateral strategy, multinational governmental organizations are discovering that green chemistry as a nonregulatory, science-based approach, provides opportunities for innovation and economic development that are compatible with sustainable development. In addition, individual nations have been extremely active in green chemistry and provide plentiful examples of the successful utilization of green chemistry technologies. There are rapidly growing activities in government, industry, and academia in the United States, Italy, the United Kingdom, the Netherlands, Spain, Germany, Japan, China, and many other countries in Europe and Asia, that testify to the importance of green chemistry to the future of the central science of chemistry around the world.Organizations and Commissions currently involved in programs in green chemistry at the national or international level include, for example:U.S. Environmental Protection Agency (EPA), with the "Green Chemistry Program" which involves, among others, the National Science Foundation, the American Chemical Society, and the Green Chemistry Institute;European Directorate for R&D (DG Research), which included the goals of sustainable chemistry in the actions and research of the European Fifth Framework Programme;Interuniversity Consortium "Chemistry for the Environment", which groups about 30 Italian universities interested in environmentally benign chemistry and funds their research groups;UK Royal Society of Chemistry, which promotes the concept of green chemistry through a "UK Green Chemistry Network" and the scientific journal Green Chemistry;UNIDO-ICS (International Centre for Science and High Technology of the United Nations Industrial Development Organization) which is developing a global program on sustainable chemistry focusing on catalysis and cleaner technologies with particular attention to developing and emerging countries (the program is also connected with UNIDO network of centers for cleaner production); andMonash University, which is the first organization in Australia to undertake a green chemistry program.Footnotes:1. The terminology "green chemistry" or "sustainable chemistry" is the subject of debate. The expressions are intended to convey the same or very similar meanings, but each has its supporters and detractors, since "green" is vividly evocative but may assume an unintended political connotation, whereas "sustainable" can be paraphrased as "chemistry for a sustainable environment", and may be perceived as a less focused and less incisive description of the discipline. Other terms have been proposed, such as "chemistry for the environment" but this juxtaposition of keywords already embraces many diversified fields involving the environment, and does not capture the economic and social implications of sustainability. The Working Party decided to adopt the term green chemistry for the purpose of this overview. This decision does not imply official IUPAC endorsement for the choice. In fact, the IUPAC Committee on Chemistry and Industry (COCI) favors, and will continue to use sustainable chemistry to describe the discipline.2. J. Elkington, < http://www.sustainability.co.uk/sustainability.htm

Mechanistic and synthetic studies in organometallic chemistry have provided considerable insight into olefin metathesis and Ziegler-Natta polymerization. New homogeneous olefin metathesis catalysts based on high oxidation state transition metals have opened new opportunities in polymer synthesis by providing unprecedented control in ring-opening polymerization of cyclic alkenes. The recent development of living coordinative polymerization systems has led to the preparation of a number of new, interesting materials, including block copolymers, conducting polymers or precursors, and ionophoric polymeric substrates.

Mixed lead–tin hybrid perovskite alloy CH3NH3(Pb1–x Sn x )­I3 attracted significant attention lately because of the reduction of its band gap below both end compounds, which makes it a promising bottom cell material in all-perovskite tandem solar cells. The effect is a consequence of a strongly nonlinear dependence of the alloy band gap on chemical composition. Here, we use electronic structure calculations at different levels of theory (density functional theory (DFT), hybrid DFT, and QSGW, with and without spin–orbit interactions) to investigate the presently elusive origin of this effect. Contrary to current conflicting studies, our results show that neither spin–orbit interactions nor the composition induced changes of the crystal structure and ordering of atoms contributes to the nonlinearity of the band gap. We find that the strong nonlinearity is primarily a consequence of chemical effects, i.e., the mismatch in energy between s and p atomic orbitals of Pb and Sn, which form the band edges of the alloy. These results unravel the nature of the band gap bowing in Sn/Pb hybrid perovskite alloys and offer a relatively simple way to estimate evolution of the band gap in other hybrid perovskite alloys.

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