Abstract:

Ammonia(NH₃) is the main raw material of nitrogen fertilizer production, and it is also an important indirect source of PM_2.5.The ammonia emission reduction and recycling are the necessary ways for green development, especially under the green industrial production cycle.Adsorption method has the noteworthy feature of the ammonia capture without phase change and the advantages that enrichment of ammonia can be directly related to carbon dioxide synthesis of nitrogen fertilizer(such as urea).This work studies the ammonia adsorption properties of the flexible reversible transformation MOFs material Cu(BDC).Three dimensional dense structure of Cu(BDC)(DMF) is prepared by hydrothermal method, and one-dimensional pore structure Cu(BDC) was obtained after the removal of DMF under heating at high temperature with changed crystal structure.The Cu(BDC) has the surface area of 535 m²·g^-1 and the adsorption capacity of pure ammonia up to 18.4 mmol·g^-1 in an atmospheric pressure, which is higher than the traditional adsorbent and other new porous materials such as MOFs and COFs.By reducing the pressure and vacuum heating, the Cu(BDC) can be progressively regenerated and thus has excellent “ammonia” characteristics.Additionally, Cu(BDC)(DMF) can be converted into Cu(BDC)(NH₃)₂ in the ammonia environment, eliminating the process of Cu(BDC) preparation.

Key words: nitrogen fertilizer, PM_2.5, ammonia, adsorbents, metal-organic frameworks, reversible transformation

摘要：

氨气（NH₃）作为氮肥合成的主要原料和PM_2.5的重要间接来源，在工业生产倡导绿色循环的大势之下，减排与回收是绿色发展的必行之路。基于吸附法具有氨气无相变，富集得到的氨气可以直接与二氧化碳反应合成氮肥（如尿素）的优势，研究了具有可逆转化性质的柔性MOFs材料Cu（BDC）的氨气吸附性能。实验中通过水热法制备了三维致密结构的Cu（BDC）（DMF），高温加热脱除DMF后晶体结构发生改变，得到了具有一维孔道结构的Cu（BDC）材料，比表面积为535 m²·g^-1，纯氨气的吸附量在一个大气压下高达18.4 mmol·g^-1，高于传统吸附剂以及其他新型的多孔MOFs和COFs等材料，并且通过减压和加热，材料可以逐步实现再生，具有优良的“载氨”特性。直接制备的Cu（BDC）（DMF）也可以在氨气的环境中（DMF被NH₃替代）转变为Cu（BDC）（NH₃）₂，省去了制备Cu（BDC）的过程。

关键词: 氮肥, PM_2.5, 氨气, 吸附剂, 金属有机骨架, 可逆转化