Synthesis Of Controllable Microporous Materials And Their Applications In Gas Separation By Adsorption

Environmental problems and energy shortages caused by the rapid consumption of fossil energy have become critical issues in recent years.Gas separation is a key technology in the process of toxic gas removal and clean energy purification in the environment.Adsorption separation technology has the advantages of low energy consumption and environmental friendliness,which is considered to be an ideal gas separation technology.However,traditional adsorbent materials possess“trade-off”effect between adsorption capacity and selectivity,which restricted the development and application of adsorption separation technology.Therefore,it is of great significance to develop new adsorption materials with high capacity and high selectivity at the same time.As adsorbents,microporous materials have advantages in gas adsorption and separation.Therefore,this work will concentrate on investigating microporous carbon materials and microporous metal organic frameworks?MOFs?.By optimizing the preparation conditions,the pore size and surface chemistry were precisely controlled.Thus,several types of microporous carbon materials and MOFs materials were synthesized.Besides,the materials were systematically characterized,the gases?CO₂,SO₂,C₂H₂?adsorption-desorption isotherms and the separation performance of two-binary mixtures were also measured,which further verify the application prospects of these materials as gas separation adsorbents.We introduce our works as follows:?1?Agricultural waste oil tea shell was used as carbon source,traditionally,biomass-derived carbons,via chemical activation process,posse wide pore size distributions from micropores to macropores.Outstanding BET surface area of 2676m² g^-1 was obtained with excellent CO₂ uptake of 6.15 and 2.26 mmol g^-1 under 1 bar and 0.15 bar at 273 K.Furthermore,the outstanding CO₂/N₂,CO₂/CH₄,and CH₄/N₂selectivities of 43.5,7.4,and 5.9 were obtained on OTS-1-550 at 298 K and 1 bar.The pore size effect on CO₂ capture and gas-separation performance was carefully investigated,indicating that the ultramicropores?<1 nm?governed the CO₂ adsorption capacity at 1 bar.Besides,the vacuum swing adsorption?VSA?processes and breakthrough experiments have confirmed their practical application potential,the solid waste was successfully converted into functional materials.?2?Ultra-high surface area and nitrogen-rich porous carbons are prepared via a low-temperature and one-pot N-doping method.The obtained carbons exhibited a large surface area of 2965.7 m² g^-1 and a high N-doping level of 6.6 at%,endowing them as efficient gas-mixture selective adsorbents.By optimizing the ratio of porogen/carbon or activation temperature,the as-prepared N-rich microporous carbons possessed outstanding mixed-gas selectivities of CO₂/N₂?77.9?,CO₂/CH₄?12.8?,and CH₄/N₂?4.9?at 298 K and 1 bar.Furthermore,three samples with almost identical surface properties were successfully prepared by judicious selection of activation conditions,thus the favorable effect of pyrrole/pyridine?N-5?species on gas-mixture separation could be demonstrated.?3?A microporous metal–organic framework?ELM-12?with specific polar sites and proper pore size for the highly efficient removal of SO₂ from flue gas and other SO₂-containing gases was reported.A high SO₂ capacity of 61.2 cm³ g^-1 combined with exceptionally outstanding selectivity of SO₂/CO₂?30?,SO₂/CH₄?871?,and SO₂/N₂?4064?under ambient conditions?i.e.,10:90 mixture at 298 K and 1 bar?were achieved.Notably,the SO₂/N₂ selectivity is unprecedented among ever reported values of porous materials.Moreover,the DFT-D calculations illustrated the superior SO₂ capture ability and selectivity arise from the high density SO₂ binding sites of CF₃SO₃^-group in the pore cavity(S^?+···O^?-interactions)and aromatic linkers in the pore walls(H^?+···O^?-interactions).Dynamic breakthrough experiments confirm the regeneration stability and excellent separation performance.Furthermore,ELM-12 is also stable after exposure to SO₂,water vapor,and organic solvents.?4?A microporous metal–organic framework Cu₂?pzdc?₂?pyz?[CPL-1,pzdc=2,3-pyrazinedicarboxylate;pyz=pyrazine]with dumbbell shaped 1D channel and specific binding sites is explored for deep desulfurization.The proper size of 4.1×6.2?and strong SO₂ trapping sites on CPL-1 render a high adsorption uptake of SO₂(44.8 cm³g^-1)with a record-high selectivity for SO₂/N₂?368?and SO₂/CH₄?74.3?separation at ambient conditions.Moreover,the dispersion-corrected density functional theory calculations have identified the dual specific adsorption sites of SO₂,such as S^?+···O^?-electrostatic interactions and O^?-···H^?+hydrogen bonds.The feasibility of CPL-1 for SO₂/N₂,SO₂/CH₄,CO₂/CH₄,CO₂/N₂,and mimicked flue gas mixture separations were validated by dynamic breakthrough experiments.Water vapor and CO₂ impurity were introduced to the gas feed streams to confirm the excellent separation performance of CPL-1.Moreover,a scale-up production of CPL-1 via a facile and green method was conducted,and reproducible CPL-1 adsorbent with undamaged adsorption and separation performances was successfully manufactured in kilogram quantity.These unique features render CPL-1 a very promising adsorbent for practical desulfurization processes.?5?During the production of polymer grade ethylene,the content of acetylene?1%?in ethylene needs to be reduced to 40 parts per million.We herein report a metal-organic framework MOF[Cu?dps?₂?MF₆?]·6H₂O?MF₆-Cu-dps??M=Si or Ge?with flexible properties can effectively remove acetylene from acetylene/ethylene mixtures.At 298K and 1 bar,the adsorption capacity of C₂H₂ reach 4.57 mmol g^-1,and the IAST selectivity is greater than 10⁹.Molecular dynamics simulation shows its specific binding site and unique pores.What's more,the purity of the obtained ethylene was over 99.9995%,and the actual separation ability was confirmed by breakthrough experiment.