利用柔性多孔晶体高效储存/分离乙炔和二氧化碳

乙炔在工业和科学研究中非常重要,但其高活性（高纯乙炔的安全压缩压力小于2个大气压）限制了其存储与运输。此外,乙炔与二氧化碳具有相似的分子尺寸和物理性质,使得对其吸附分离变得困难。本项研究通过在多孔金属多氮唑框架（MAF）的孔道开口加入柔性侧基,获得了一个具有开关效应的新型多孔材料（MAF-2）。研究显示,合理的孔道表面结构加上柔性框架与动态侧基的协同效应,令MAF-2具备了独特的乙炔和二氧化碳吸附行为。该材料对乙炔的饱和吸附能力可达到119cm3g-1,而且常温常压下也可达到70cm3g-1。更重要的是,该材料的柔性行为使其吸附等温线不同于常规多孔材料。在实际应用条件下,MAF-2的乙炔吸附量随着压力增加而快速增加。在298K,1.0—1.5个大气压之间,MAF-2可以存储20倍其体积的乙炔,相当于同体积气体钢瓶有效储量的40倍。此外,在常温常压下,该材料具有非常高的乙炔/二氧化碳吸附比（3.7）,可望应用于这两种气体的分离,并减少吸附分离过程中的能耗。

Optimized Acetylene/Carbon Dioxide Sorption in a Dynamic Porous Crystal

The low compression limit of acetylene （C2H2） and its similarity to carbon dioxide （CO2） challenge the development of novel adsorbents.We illustrate in this report that the unique static and dynamic pore characteristics of a metal azolate framework,Cu（etz）]n （MAF-2,Hetz = 3,5-diethyl-1,2,4-triazole）,can combine to show extraordinary C2H2/CO2 sorption behaviors,which have been elucidated by a combination of gas sorption measurements and single-crystal structure analyses of the sorption complexes of both C2H2 and CO2.As demonstrated by single-crystal X-ray crystallography,C2H2/CO2 hexamers are confined inside the nanocages of MAF-2 in different configurations.The subtle difference between C2H2 and CO2 is magnified by consequent framework dynamics,which produce sigmoid isotherms that are optimized for practical adsorptive applications.Large C2H2 uptake （70 cm3 g-1） and high C2H2/CO2 uptake ratio （3.7） at 298 K,1 atm as well as facile gas desorption are revealed.Since the C2H2 uptake at 298 K,1 atm is far from saturation （119 cm3 g-1）,MAF-2 permits a usable C2H2 storage capacity 20 times higher than its volume or 40 times higher than that of a gas cylinder working between practical limits of 1.0—1.5 atm.