配体插入型疏水微孔MOFs的设计构筑及燃烧后碳捕集性能研究

Porous metal-organic frameworks(MOFs) are the most promising adsorbent for carbon dioxide post-combustion capture. However, the hydrothermal stability and cycle life capability within thousands of sorption/desorption are still the main problems for their practical application at the conditions of flue gas of power plants.For the low partial pressure of carbon dioxide and water co-existing environment of flue gas, this research uses symmetry-matching ligand insertion pore space partition novel strategy and MIL type MOFs as prototype frameworks to tune and contruct the hydrophobic microporous MOFs with highly hydrothermal stability by introducing the N-heterocycle in the insertion ligand and methyl groups in primary ligand and using high covalent metal cations. The reserch focuses on the relationship between factors of metal cations, primary ligand, insertion ligand, pore structure and chemistry property and its adsorption capability for post-combustion carbon dioxide capture and hydrothermal stability, including the effect of impurities of H2O, O2,NOX,SO2 on carbon dioxide capture capability and the intrinsic mechanism. The MOFs constructed are characterized by powder X-ray diffraction(PXRD), N2 adsorption and desorption, SEM, TEM and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) methods. By using fixed-bed adsorption dynamic breakthrough method and simulating the condition of flue gas, the effects of impurities of H2O, O2,NOX,SO2 on adsorption capability of carbon dioxide are examined and the mechanism for the effect of impurities on adsorption capability by in-situ diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometer(DRIFTS/MS) method. This research has important scientific significance and application value for the study of structure-activity relationship between the construction of hydrophobic microporous metal-organic frameworks adsorbent with hydrothermal stability based on symmetry-matching ligand insertion pore space partition strategy and gas separation capability and the realization of adsorption performance adjustment.

多孔金属有机骨架材料（MOFs）是用于燃烧后碳捕集最具前景吸附剂，尚存在烟气环境下水热稳定性和循环寿命问题。本研究针对燃烧后捕集CO2低分压和水共存环境，采用对称配体孔分隔新方法，以较稳定MIL-88为原型骨架，在插入配体中引入氮杂环，主配体中引入甲基官能团，采用高价金属阳离子，调控构筑高水热稳定性疏水微孔新型MOFs吸附剂，研究不同金属离子、不同主配体、插入配体、孔结构和表面特性与碳捕集性能和水热稳定性构效关系及水、O2、NOX、SO2等杂质对吸附性能影响和作用机制。研究采用PXRD、 N2吸附脱附、SEM、TEM、DRIFTS表征结构；在模拟烟气条件下研究各杂质对吸附性能和循环耐久性影响；通过原位DRIFTS/MS研究杂质对吸附性能影响机理。研究对揭示基于配体插入孔分隔法构筑高水热稳定性疏水微孔MOFs吸附剂与气体分离性能构效关系和作用机制及实现性能调控具有重要科学意义和应用价值。

项目研究采用对称配体孔分隔新方法，以较稳定MIL-88为原型骨架，在插入配体中引入氮杂环，主配体中引入甲基官能团，采用高价金属阳离子，调控构筑高水热稳定性疏水微孔新型MOFs吸附剂，研究了不同金属离子、不同主配体、插入配体、孔结构和表面特性与碳捕集性能和水热稳定性构效关系及烟道气杂质对吸附性能影响和作用机制。研究表明：孔分割MIL-88新型MOFs吸附剂是新型合成平台，在金属离子、主配体和插入配体选择上均具有多样性和可调控性，在吸附小分子气体中具有广阔应用前景。在常温低压下吸附气体小分子，获得微孔孔径与分子大小相当，并对吸附剂表面作用力和有效吸附位密度进行调控是获得大吸附容量的关键因素。采用热重分析仪对新型吸附剂进行热稳定性研究，研究表明制备的吸附剂在200℃以下具有较好的热稳定性。在烟气环境下，新型MOFs吸附剂对CO2具有较好的吸附性能。研究对揭示基于配体插入孔分隔法构筑高水热稳定性疏水微孔MOFs吸附剂与气体分离性能构效关系及实现性能调控具有重要科学意义。