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

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