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Metal-organic Framework
METAL–ORGANIC FRAMEWORKS (MOFs) are compounds consisting of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. They are a subclass of coordination polymers , with the special feature that they are often porous . The organic ligands included are sometimes referred to as "struts", one example being 1,4-benzenedicarboxylic acid (BDC). More formally, a metal–organic framework is a coordination network with organic ligands containing potential voids. A coordination network is a coordination compound extending, through repeating coordination entities, in one dimension, but with cross-links between two or more individual chains, loops, or spiro-links, or a coordination compound extending through repeating coordination entities in two or three dimensions; and finally a coordination polymer is a coordination compound with repeating coordination entities extending in one, two, or three dimensions
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Specific Surface Area
SPECIFIC SURFACE AREA (SSA) is a property of solids defined as the total surface area of a material per unit of mass , (with units of m2/kg or m2/g) or solid or bulk volume (units of m2/m3 or m−1). It is a derived scientific value that can be used to determine the type and properties of a material (e.g. soil or snow ). It has a particular importance for adsorption , heterogeneous catalysis , and reactions on surfaces . CONTENTS* 1 Measurement * 1.1 Calculation * 1.2 Adsorption
Adsorption
* 1.3 Gas permeability * 2 See also * 3 References MEASUREMENTValues obtained for specific surface area depend on the method of measurement. In adsorption based methods, the size of the adsorbate molecule (the probe molecule), the exposed crystallographic planes at the surface and measurement temperature all affect the obtained specific surface area
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Energy Storage
ENERGY STORAGE is the capture of energy produced at one time for use at a later time. A device that stores energy is sometimes called an accumulator . Energy
Energy
comes in multiple forms including radiation, chemical , gravitational potential , electrical potential , electricity, elevated temperature, latent heat and kinetic . Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms. Bulk energy storage is currently dominated by hydroelectric dams, both conventional as well as pumped. Some technologies provide short-term energy storage, while others can endure for much longer
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Gas Cylinder
A GAS CYLINDER or tank is a pressure vessel used to store gases at above atmospheric pressure . High-pressure gas cylinders are also called bottles, but a bottled gas may instead be in a liquid or dissolved state in the cylinder. CONTENTS * 1 Nomenclature differences * 2 History * 3 Materials * 4 Regulations and cylinder testing * 5 Valve connections * 6 Safety and standards * 6.1 International and national standards * 6.2 Color coding * 7 Common cylinder sizes * 8 See also * 9 References * 10 External links NOMENCLATURE DIFFERENCESIn the United States, "bottled gas" typically refers to liquefied petroleum gas . "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tanks . Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used
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Adsorption
ADSORPTION is the adhesion of atoms , ions , or molecules from a gas, liquid, or dissolved solid to a surface . This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption , in which a fluid (the absorbate) is dissolved by or permeates a liquid or solid (the absorbent), respectively. Adsorption is a surface-based process while absorption involves the whole volume of the material. The term sorption encompasses both processes, while desorption is the reverse of it. Adsorption
Adsorption
is a surface phenomenon . IUPAC Definition Increase in the concentration of a substance at the interface of a condensed and a liquid or gaseous layer owing to the operation of surface forces. Note 1: Adsorption
Adsorption
of proteins is of great importance when a material is in contact with blood or body fluids
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Molecule
A MOLECULE is an electrically neutral group of two or more atoms held together by chemical bonds . Molecules are distinguished from ions by their lack of electrical charge . However, in quantum physics , organic chemistry , and biochemistry , the term molecule is often used less strictly, also being applied to polyatomic ions . In the kinetic theory of gases , the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear , that is, it consists of atoms of one chemical element , as with oxygen (O2); or it may be heteronuclear , a chemical compound composed of more than one element, as with water (H2O). Atoms and complexes connected by non-covalent interactions , such as hydrogen bonds or ionic bonds , are generally not considered single molecules
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Specific Energy
SPECIFIC ENERGY is energy per unit mass . (It is also sometimes called "energy density," though "energy density" more precisely means energy per unit volume .) It is used to quantify, for example, stored heat or other thermodynamic properties of substances such as specific internal energy , specific enthalpy , specific Gibbs free energy
Gibbs free energy
, and specific Helmholtz free energy
Helmholtz free energy
. It may also be used for the kinetic energy or potential energy of a body. Specific energy is an intensive property , whereas energy and mass are extensive properties
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Hydrogen Storage
Methods of HYDROGEN STORAGE for subsequent use span many approaches including high pressures, cryogenics, and chemical compounds that reversibly release H2 upon heating. Underground hydrogen storage is useful to provide grid energy storage for intermittent energy sources , like wind power , as well as providing fuel for transportation, particularly for ships and airplanes. Most research into hydrogen storage is focused on storing hydrogen as a lightweight, compact energy carrier for mobile applications . Liquid hydrogen
Liquid hydrogen
or slush hydrogen may be used, as in the Space Shuttle . However liquid hydrogen requires cryogenic storage and boils around 20.268 K (−252.882 °C or −423.188 °F). Hence, its liquefaction imposes a large energy loss (as energy is needed to cool it down to that temperature). The tanks must also be well insulated to prevent boil off but adding insulation increases cost
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Chemisorption
CHEMISORPTION is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbant surface. Examples include macroscopic phenomena that can be very obvious, like corrosion , and subtler effects associated with heterogeneous catalysis . The strong interaction between the adsorbate and the substrate surface creates new types of electronic bonds . In contrast with chemisorption is physisorption , which leaves the chemical species of the adsorbate and surface intact. It is conventionally accepted that the energetic threshold separating the binding energy of "physisorption" from that of "chemisorption" is about 0.5 eV per adsorbed species . Due to specificity, the nature of chemisorption can greatly differ, depending on the chemical identity and the surface structure
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Platinum
PLATINUM is a chemical element with symbol PT and atomic number 78. It is a dense , malleable , ductile , highly unreactive, precious , gray-white transition metal . Its name is derived from the Spanish term platina, meaning "little silver". Platinum
Platinum
is a member of the platinum group of elements and group 10 of the periodic table of elements . It has six naturally occurring isotopes . It is one of the rarer elements in Earth\'s crust , with an average abundance of approximately 5 μg /kg. It occurs in some nickel and copper ores along with some native deposits, mostly in South Africa , which accounts for 80% of the world production. Because of its scarcity in Earth's crust, only a few hundred tonnes are produced annually, and given its important uses, it is highly valuable and is a major precious metal commodity . Platinum
Platinum
is one of the least reactive metals
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Activated Carbon
ACTIVATED CARBON, also called ACTIVATED CHARCOAL, is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions . Activated is sometimes substituted with active. Due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 3,000 m2 (32,000 sq ft), as determined by gas adsorption . An activation level sufficient for useful application may be attained solely from high surface area; however, further chemical treatment often enhances adsorption properties. Activated carbon
Activated carbon
is usually derived from charcoal and is sometimes utilized as biochar . Those derived from coal and coke are referred as ACTIVATED COAL and ACTIVATED COKE respectively
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Hydrogen Spillover
In heterogeneous catalysis , hydrogen molecules can be adsorbed and dissociated by the metal catalyst. The migration of hydrogen atoms from the metal catalyst onto the nonmetal support or adsorbate comprise the spillover phenomenon. Spillover, generally, is the transport of a species adsorbed or formed on a surface onto another surface. Hydrogen spillover can be characterized by three major steps, the first being where molecular hydrogen is split via dissociative chemisorption into its constitutive atoms on a transition metal catalyst surface, followed by migration from the catalyst to the substrate, culminating in their diffusion throughout the substrate surfaces and/or in the bulk materials. CONTENTS* 1 Mechanism and Trends * 1.1 Mechanism * 1.2 Trends * 2 Applications * 3 References MECHANISM AND TRENDSMECHANISMThe mechanism behind hydrogen spillover has been long disputed
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Atom
An ATOM is the smallest constituent unit of ordinary matter that has the properties of a chemical element . Every solid , liquid , gas , and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale ). Atoms are small enough that attempting to predict their behavior using classical physics – as if they were billiard balls, for example – gives noticeably incorrect predictions due to quantum effects . Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons . Protons and neutrons are called nucleons . More than 99.94% of an atom's mass is in the nucleus
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Physisorption
PHYSISORPTION, also called PHYSICAL ADSORPTION, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption . CONTENTS * 1 Introduction * 2 Modeling by image charge * 3 Modeling by quantum-mechanical oscillator * 4 Physisorption potential * 5 Comparison with chemisorption * 6 See also * 7 References INTRODUCTIONThe fundamental interacting force of physisorption is caused by van der Waals force . Even though the interaction energy is very weak (~10–100 meV), physisorption plays an important role in nature. For instance, the van der Waals attraction between surfaces and foot-hairs of geckos provides the remarkable ability to climb up vertical walls. Van der Waals forces originate from the interactions between induced, permanent or transient electric dipoles
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Covalent Organic Framework
COVALENT ORGANIC FRAMEWORKS (COFS) are two-dimensional and three-dimensional organic solids with extended structures in which building blocks are linked by strong covalent bonds . COFs are porous and crystalline and are made entirely from light elements (H, B, C, N, and O) that are known to form strong covalent bonds in well-established and useful materials such as diamond , graphite , and boron nitride . Preparation of COF materials from molecular building blocks would provide covalent frameworks that could be functionalized into lightweight materials for diverse applications
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Azole
AZOLES are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom (i.e. nitrogen , sulfur , or oxygen ) as part of the ring. Their names originate from the Hantzsch–Widman nomenclature . The parent compounds are aromatic and have two double bonds ; there are successively reduced analogs (azolines and azolidines ) with fewer. One, and only one, lone pair of electrons from each heteroatom in the ring is part of the aromatic bonding in an azole. Names of azoles maintain the prefix upon reduction (e.g., pyrazoline , pyrazolidine ). The numbering of ring atoms in azoles starts with the heteroatom that is not part of a double bond, and then proceeds towards the other heteroatom. Imidazole and other five-membered aromatic heterocyclic systems with two nitrogens are extremely common in nature and form the core of many biomolecules , such as histidine
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