Efficient One-Step Purification of C1 and C2 Hydrocarbons over CO2 in a New CO2‑Selective MOF with a Gate-Opening Effect

Removing CO2 impurity is an essential industrial process in the purification of hydrocarbons. The most promising strategy is the one-step collection of high-purity hydrocarbons by employing CO2-selective adsorbents, which requires improving the CO2 adsorption and separation behavior of adsorbents, especially the low-pressure performance under actual industrial conditions. Herein, we constructed a new flexible metal–organic framework [Zn­(odip)0.5(bpe)0.5(CH3OH)]·0.5NMF·H2O (1) (H4odip = 5,5′-oxydiisophthalic acid, bpe = 1,2-bi­(4-pyridyl)­ethylene, and NMF = N-methylformamide) containing rich ether O adsorption sites in the channels that exhibits remarkable adsorption capacity for CO2 (118.7 cm3 g–1) due to the only gate-opening-type abrupt adsorption of CO2 at room temperature. Its low affinity for other competing gases enables it to deliver high selectivity for the adsorption of CO2 over C1 and C2 hydrocarbons. For equimolar mixtures of CO2–CH4 and CO2–C2H2, the selectivities are 376.0 and 13.2, respectively. Molecular simulations disclose more abundant adsorption sites for CO2 than hydrocarbons in 1. The breakthrough separation performances combined with remarkable stability and recyclability further verify that 1 is a promising adsorbent that can efficiently extract high-purity hydrocarbons through selective capture of CO2.

脱除二氧化碳（CO₂）杂质是烃类纯化过程中的关键工业步骤。当前最具应用潜力的策略是借助二氧化碳选择性吸附剂一步制备高纯度烃类，该技术亟需优化吸附剂的二氧化碳吸附与分离性能，尤其是在实际工业工况下的低压吸附表现。本研究中，我们构建了一种新型柔性金属有机框架（metal–organic framework）材料[Zn(odip)₀.₅(bpe)₀.₅(CH₃OH)]·0.5NMF·H₂O (1)，其中H₄odip代表5,5'-氧二间苯二甲酸，bpe代表1,2-双(4-吡啶基)乙烯，NMF为N-甲基甲酰胺（N-methylformamide）。该框架的孔道内富含醚氧吸附位点，在室温下仅对二氧化碳表现出开门型突跃吸附，因此对二氧化碳展现出优异的吸附容量（118.7 cm³·g⁻¹）。相较于其他竞争气体，该吸附剂对其亲和力极低，因此对二氧化碳与C1、C2烃类的吸附展现出极高的选择性。针对CO₂–CH₄与CO₂–C₂H₂的等摩尔混合体系，其选择性分别可达376.0与13.2。分子模拟结果表明，该框架中二氧化碳的吸附位点数量多于烃类分子。穿透分离性能结合其优异的稳定性与可回收性，进一步证实该吸附剂可通过选择性捕获二氧化碳高效提取高纯度烃类，是一款极具应用前景的吸附材料。