物理吸附Physisorption

吸附热一般为 5–40 kJ/mol，与吸附质的液化热相近；不需要活化能，几乎瞬间达到平衡；降低压力或升高温度即可脱附，吸附质分子结构不变；任何气体在任何固体表面都会发生物理吸附，越易液化的气体（沸点越高）吸附量越大；低温下吸附量大，可在单层之上继续吸附形成多层。

Heats of adsorption are typically 5–40 kJ/mol, close to the heat of liquefaction; no activation energy is needed, so equilibrium is reached almost instantly; lowering the pressure or raising the temperature desorbs the adsorbate unchanged; every gas physisorbs on every solid, and gases that liquefy more easily (higher boiling points) adsorb more; uptake is large at low temperature and can continue beyond a monolayer into multilayers.

77 K 下氮气在固体表面的物理吸附是测定比表面积（BET 法）和孔径分布（BJH 法、密度泛函法）的标准方法。IUPAC 把吸附等温线分为六类（I–VI 型），I 型对应微孔材料，IV 型带滞后环对应介孔材料。活性炭比表面积可达 1000–3000 m²/g，某些金属有机框架超过 7000 m²/g。

Nitrogen physisorption at 77 K is the standard method for specific surface area (BET) and pore-size distribution (BJH and density-functional methods). IUPAC classifies isotherms into six types, I to VI: type I indicates micropores and type IV, with a hysteresis loop, mesopores. Activated carbon reaches 1000–3000 m²/g, and some metal–organic frameworks exceed 7000 m²/g.

物理吸附用于活性炭除味脱色、硅胶和分子筛干燥、变压吸附分离空气（沸石分子筛优先吸附 N₂ 制氧）、储存甲烷和氢气，以及气相色谱的固定相分离。

Physisorption is used for odour and colour removal with activated carbon, drying with silica gel and molecular sieves, air separation by pressure-swing adsorption (zeolites preferentially take up N₂ to give oxygen), methane and hydrogen storage, and separation on gas-chromatography stationary phases.