Abstract:

The development of functional porous crystalline materials driven by physical adsorption for deep removal of CO₂ impurities from crude syngas is an important way to produce high quality syngas. Although well-known metal organic framework (MOFs) has made many breakthroughs in CO₂ capture, it often suffers from the key problems of decreasing adsorption capacity and low product purity in μL/L CO₂ capture and non-room temperature CO₂/CO purification. Based on this, the classical Mg-MOF-74 (1a) was taken as the research object and aminopyrazine motif (apz) could be successfully confined to the 1a channel (1a-apz) by a facile steam-coordination strategy. The results showed that 1a-apz had outstanding separation performance for 1/99 CO₂/CO mixture, and the purity and yield of CO were 99.99% and 70.5L/kg, respectively, at the operating temperature of 348K. Crude syngas containing the mixtures of H₂/N₂/CH₄/CO/CO₂ (46/18.3/2.4/32.3/1, volume fraction) confirmed that 1a-apz remained prominent trace CO₂ capture performance. In situ gas-loaded crystal diffraction, temperature-dependent spectroscopy tests, high-resolution synchrotron radiation X-ray diffraction and theoretical calculations revealed that the apz motif in 1a-apz structure not only had "adaptive adsorption" behavior at the appropriate threshold temperature, but also could effectively regulate the local electrostatic potential of pore surface and confine the functionalized multiple adsorption sites. Thus, yielded "induction-fit" behavior between CO₂ and pore surface would form, which was similar to the "enzyme-substrate" identification process in the biological world.

Key words: syngas, metal-organic frameworks (MOFs), "induced-fit"identification, carbon dioxide capture, CO₂/CO separation

摘要：

开发物理吸附驱动的功能化多孔晶态材料用于粗合成气中CO₂杂质深度去除是生产高质量合成气的重要途径。尽管金属有机框架材料（metal organic framework，MOFs）在CO₂捕获方面取得了诸多突破，但在面临痕量CO₂捕集和非室温CO₂/CO提纯方面常有吸附量下降和产品纯度低等关键问题。基于此，本文以经典的Mg-MOF-74（1a）为研究对象，通过温和的蒸汽配位策略可将氨基吡嗪基元（apz）成功地限域在1a孔道中（1a-apz）。结果表明，1a-apz对1/99的CO₂/CO混合组分有突出的分离性能，且在348K工况温度下，CO产品纯度和产率分别为99.99%和70.5L/kg。粗合成气H₂/N₂/CH₄/CO/CO₂（体积比46/18.3/2.4/32.3/1）穿透实验证实1a-apz仍保持突出的痕量CO₂捕集性能。原位气体负载晶态衍射、变温光谱测试、原位高分辨同步辐射X射线衍射和理论计算等手段揭示了1a-apz 结构中的apz基元在适宜阈值温度下不仅会发生“吸附自适应”行为，还可以有效调控孔隙局域静电势和限域功能化多重吸附位点，从而实现CO₂与孔表面形成类似生物界“酶-底物”辨识过程的“诱导-契合”行为。

关键词: 合成气, 金属有机框架材料, “诱导-契合”辨识, CO₂捕集, CO₂/CO分离