Enhanced CO_2/N_2 separation performance in HP-Cu-BTCs by modifying the open-metal sites and porosity using added templates

摘要

HP-Cu-BTCs (CTAB), HP-Cu-BTC(N,N), HP-Cu-BTC(SDBS) series with open metal coordination site Cu(I), cage window sites, tunable porosity, high specific surface area, cavity, etc., were synthesized using cationic surfactant (cetyltrimethylammonium bromide, neutral organic amine, and an anionic surfactant as templates, respectively, A variety of techniques were used to analyze the materials before and after CO_2 cycle adsorption at 303 K. A high BET specific surface area (1,194.06 m~2/g) and total pore volume (0.63 cm~3/g) were found in the synthesized HP-Cu-BTC(N,N). The synthesized HP-Cu-BTC(N,N) not only has high CO_2 adsorption capacity (7.4293 mmol/g) but also good selectivity (37.20) for adsorption separation of CO_2/N_2. Besides, FT-IR spectroscopy, CO_2-TPD curves and adsorption kinetic curve demonstrated that the adsorption mechanism of synthesized HP-Cu-BTC(N,N) was mainly attributable to phy-sisorption and it could be regenerated at relatively low temperature. The mesoporous structure not only improves the uptake capacity but also improves the diffusion and mass transfer of CO_2. At the same time, the CO_2-TPD showed that the HP-Cu-BTCs may have two major adsorption sites. One is to absorb CO_2 molecules through van der Waals forces. The other is the electrostatic interaction of the open Cu sites with CO_2. Therefore, the CO_2/N_2 adsorption selectivity of HP-Cu-BTC(N,N) is significantly higher than that of conventional Cu-BTC. After five consecutive adsorption/desorp-tion cycles, the adsorbents retained an excellent adsorption property. Thus, it is a very good adsorbent for the CO_2 capture.