第十五章 硼族元素 Chapter 15 The Boron Family Elements. Boron (B) Aluminum (Al) Gallium (Ga) Indium (In) Thallium (Tl) ns 2 np 1. §15-1 Boron and its compounds 一、 General properties 1. 硼的化学性质与 Si 有某些相似之处， ( 对角线相似 原则 ) ，通常硼呈现 +3 氧化态，负氧化态的情况很少。
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第十五章 硼族元素Chapter 15 The Boron Family Elements
Boron (B) Aluminum (Al) Gallium (Ga)
Indium (In) Thallium (Tl)
相当于将左图中的2c2e B-B键沿键轴方向裂分成两半并分别向上和向 下移动与原有的开方式3c2e B-B-B键接合，形成4个特别的3c2e键，其中2个硼分别将各自的一个价轨道分成两半加入这4个3中心成键。也可以看作4个2.5c2e键（按价轨道计算中心数）代替了原来的2个B-B和2个B-B-B。
4620 (SEP=12, nido-，巢式结构)
Discovered in 1992, mesoporous materials are porous materials with regularly arranged, uniform mesopores (2 nm to 50 nm in diameter). Their large specific surface area, as high as 1,000 m2/g, makes them useful as catalysts or adsorbents.
Zeolites. Zeolite is a Greek word that means “boiling stone,” because naturally occurring zeolites are minerals that absorb water that subsequently boils when heated. Zeolites are microporous, crystalline aluminosilicates consisting of three components: framework tetrahedra, cations, and adsorbed molecules. Depending upon the framework and cations, the adsorbed phase feels a local electrostatic environment ranging from nonpolar to extremely polar. Three important zeolite framework topologies are shown in Figures.
The technological importance of these materials cannot be overstated. For example, it is estimated that the monetary value of zeolitic catalysis to petroleum cracking over the past several decades is in excess of 100 billion dollars. Zeolites are also used as molecular sieves for separating chemical mixtures, as ion exchangers and filters, as environmentally safe detergents, as desiccants for new coolant systems, and as hydrocarbon traps for new cold-start catalytic converters. Mesoporous sieves show promise for separating biomolecules and may be useful for making optical electronic materials with substantial quantum confinement.