There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

BACKGROUND With a rising global population, increasing energy demands, and impending climate change, major concerns have been raised over the security of our energy future. Developing sustainable, fossil-free pathways to produce fuels and chemicals of global importance could play a major role in reducing carbon dioxide emissions while providing the feedstocks needed to make the products we use on a daily basis. One prospective goal is to develop electrochemical conversion processes that can convert molecules in the atmosphere (e.g., water, carbon dioxide, and nitrogen) into higher-value products (e.g., hydrogen, hydrocarbons, oxygenates, and ammonia) by coupling to renewable energy. Electrocatalysts play a key role in these energy conversion technologies because they increase the rate, efficiency, and selectivity of the chemical transformations involved. Today’s electrocatalysts, however, are inadequate. The grand challenge is to develop advanced electrocatalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies. ADVANCES Over the past decade, substantial progress has been made in understanding several key electrochemical transformations, particularly those that involve water, hydrogen, and oxygen. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward the development of improved catalysts. Catalyst design strategies that aim to increase the number of active sites and/or increase the intrinsic activity of each active site have been successfully developed. The field of hydrogen evolution, for example, has seen important breakthroughs over the years in the development of highly active non–precious metal catalysts in acid. Notable advancements have also been made in the design of oxygen reduction and evolution catalysts, although there remains substantial room for improvement. The combination of theory and experiment elucidates the remaining challenges in developing further improved catalysts, often involving scaling relations among reactive intermediates. This understanding serves as an initial platform to design strategies to circumvent technical obstacles, opening up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions. OUTLOOK A systematic framework of combining theory and experiment in electrocatalysis helps to uncover broader governing principles that can be used to understand a wide variety of electrochemical transformations. These principles can be applied to other emerging and promising clean energy reactions, including hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, among others. Although current paradigms for catalyst development have been helpful to date, a number of challenges need to be successfully addressed in order to achieve major breakthroughs. One important frontier, for example, is the development of both experimental and computational methods that can rapidly elucidate reaction mechanisms on broad classes of materials and in a wide range of operating conditions (e.g., pH, solvent, electrolyte). Such efforts would build on current frameworks for understanding catalysis to provide the deeper insights needed to fine-tune catalyst properties in an optimal manner. The long-term goal is to continue improving the activity and selectivity of these catalysts in order to realize the prospects of using renewable energy to provide the fuels and chemicals that we need for a sustainable energy future.

/pdf/combining-theory-and-experiment-in-electrocatalysis-insights-3l4yblici7.pdf

Combining theory and experiment in electrocatalysis: Insights into materials design

Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

Noble metal-free hydrogen evolution catalysts for water splitting

Lateral thinking in biomimetic materials chemistry has permitted chemists to create fascinating structures that mimic the biomaterials optimized by Nature. The integration of organic and inorganic chemistry at multiple length scales gives optimal performance characteristics to biomaterials, such as bone. In a similar fashion, lateral thinking in our lab has enabled us to consolidate the chemistry of inorganic surfactant-templated mesoporous materials with the organic-inorganic hybrid structure of amorphous xerogels. A new class of materials, periodic mesoporous organosilicas (PMOs), has emerged that marries organic and solid-state chemistry in the channels of hexagonally ordered mesoporous materials. Various organic and organometallic groups may be integrated into the framework, creating materials with novel, tunable properties. Surfactant can be solvent-extracted or ion-exchanged to create a high surface area PMO with the framework and the organic group intact. This renders the organic groups accessible for reaction to give a new type of “chemistry of the channels”.

Periodic mesoporous organosilicas (PMOs): Nanostructured organic-inorganic hybrid materials

Nanocatalysis: Catalysis with Nanoscale Materials

In this paper, we report a simple template-free synthetic method that produces amorphous, nanoporous aluminosilicate and highly selective catalyst for toluene alkylation. The structure and composition of the material and its corresponding control material are characterized by various techniques. The material shows excellent catalytic selectivity for alkylation of toluene by tert-butyl alcohol in temperatures between 50–150 °C under atmospheric pressure, producing exclusively 4-tert-butlytoluene (ca. 99%).

Template-free synthesis of highly selective amorphous aluminosilicate catalyst for toluene alkylation

A hierarchically ordered porous carbon electrocatalyst with exclusively surface‐anchored cobalt species, dubbed Co@HOPC, is synthesized from polyaniline and cobalt‐functionalized silica microparticles templates, and its high electrocatalytic activity for the oxygen evolution reaction (OER) is demonstrated. The material requires a small potential (320 mV) to drive the reaction with a current density of 10 mA cm−2 and a small Tafel slope of 31.2 mV dec−1. Moreover, Co@HOPC shows better catalytic activity for OER than in situ cobalt‐doped and surface cobalt‐loaded hierarchically ordered porous carbon materials synthesized by traditional methods. This is due to the abundant surface cobalt species present in Co@HOPC and the material's good electrical conductivity. This work provides a new strategy to utilize functionalized silica microparticles as templates to synthesize hierarchically ordered porous carbon materials with metal‐rich surfaces and efficient electrocatalytic activities.

Hierarchically Ordered Nanoporous Carbon with Exclusively Surface‐Anchored Cobalt as Efficient Electrocatalyst

Nanoporous carbons derived from metal-conjugated phosphoprotein/silica: Efficient electrocatalysts for oxygen reduction and hydrazine oxidation reactions

Tewodros Asefa

Papers

Periodic mesoporous organosilicas (PMOs): Nanostructured organic-inorganic hybrid materials

Nanocatalysis: Catalysis with Nanoscale Materials

Template-free synthesis of highly selective amorphous aluminosilicate catalyst for toluene alkylation

Hierarchically Ordered Nanoporous Carbon with Exclusively Surface‐Anchored Cobalt as Efficient Electrocatalyst

Nanoporous carbons derived from metal-conjugated phosphoprotein/silica: Efficient electrocatalysts for oxygen reduction and hydrazine oxidation reactions