Photo-switchable smart metal organic framework membranes with tunable and enhanced molecular sieving performance

Developing a novel MOF membrane material with switchable separation performance is an exciting and challenging research project. In the present work, we report preparation of a new kind of light induced smart MOF membrane, i.e., Cu(AzDC)(4,4-BPE)(0.5) membrane, which shows (i) enhanced molecular sieving performance, and (ii) is able to respond quickly to external light stimuli. Two photo-switchable moieties are addressed in the Cu(AzDC)(4,4-BPE)(0.5) membrane: azobenzene and bis(4-pyridyl)ethylene. When the Cu(AzDC)(4,4-BPE)(0.5) membrane is in situ irradiated with Vis and UV light, the separation factor of a H-2/CO2 mixture can be switched reversibly between 21.3 and 43.7. This switching effect is mainly caused by reduced CO2 adsorption in the UV-cis state as proven by independent adsorption studies. For a steric reason, adsorption of CO2 is limited for the UV-cis state. In full agreement with this model, the adsorption of other gases H-2, CH4 and N-2 as well as their permeation behaviour is not observably influenced by the trans-cis switching.

开发一种具有可切换分离性能的新型金属 - 有机框架（MOF）膜材料是一个令人兴奋且具有挑战性的研究项目。在本研究中，我们报道了一种新型光诱导智能MOF膜的制备，即Cu(AzDC)(4,4 - BPE)(0.5)膜，它（i）具有增强的分子筛分性能，并且（ii）能够对外部光刺激快速响应。Cu(AzDC)(4,4 - BPE)(0.5)膜中存在两种光可切换部分：偶氮苯和双（4 - 吡啶基）乙烯。当Cu(AzDC)(4,4 - BPE)(0.5)膜在原位用可见光和紫外光照射时，H₂/CO₂混合物的分离因子可在21.3和43.7之间可逆切换。这种切换效应主要是由于在紫外 - 顺式状态下CO₂吸附减少所致，这已通过独立的吸附研究证实。由于空间位阻原因，在紫外 - 顺式状态下CO₂的吸附受到限制。与该模型完全一致的是，其他气体H₂、CH₄和N₂的吸附以及它们的渗透行为没有受到反式 - 顺式切换的明显影响。