Modulating the Acidic and Basic Site Concentration of Metal‐Organic Framework Derivatives to Promote the Carbon Dioxide Epoxidation Reaction

• Published in: Chemistry : a European journal Vol. 27; no. 43; pp. 11102 - 11109
• Main Authors: Ji, Jinhua, Liu, Hao, Chen, Zewei, Fu, Yajun, Yang, Weijun, Yin, Shuang‐Feng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 02.08.2021
• Subjects: Basicity; Bimetals; Carbon dioxide; carbon dioxide conversion; Catalysis; Catalytic converters; Chemistry; Cobalt; Cycloaddition; Energy storage; Epoxidation; Ions; Metal concentrations; Metal-organic frameworks; metalloporphyrin; Metals; Nitrogen; Porphyrins; Precursors; Pyrolysis; Pyrolysis products; Volatilization; Zinc
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202100430

Metal‐organic framework (MOF) is an ideal precursor/template for porous carbon, and its active components are uniformly doped, which can be used in energy storage and catalytic conversion fields. Metal‐organic framework PCN‐224 with carboxylporphyrin as the ligand was synthesized, and then Zn2+ and Co2+ ions were coordinated in the center of the porphyrin ring by post‐modification. Here, PCN‐224−ZnCo with different ratios of bimetallic Zn2+/Co2+ ions were used as the precursor, and the metal‐nitrogen‐carbon(M−N−C) material of PCN‐224−ZnCo‐950 was obtained by pyrolyzing the precursor at 950 °C in Ar. Because Zn is easy to volatilize at 950 °C, the formed M−N−C materials can reflect different Co contents and different basic site concentrations. The formed material still maintains the original basic framework. With the increase of Zn2+/Co2+ ratio in precursor, the concentration of N‐containing alkaline sites in pyrolysis products gradually increase. Compared with the precursor, PCN‐224−ZnCo1‐950 with Zn2+/Co2+=1 : 1 has greatly improved basicity and suitable acidic/ alkaline site concentration. It can be efficiently used to carbon dioxide absorption and catalyze the cycloaddition of CO2 with epoxide. More importantly, the current method of adjusting the acidic/basic sites in M−N−C materials through volatilization of volatile metals can provide an effective strategy for adjusting the catalysis of MOF derivatives with porphyrin structure. PCN‐244−ZnCo1 was successfully synthesized and then pyrolyzed to the target product PCN‐224−ZnCo1‐950 at 950 °C. The physical structure of PCN‐224−ZnCo1‐950 did not change much, as judged by SEM and N2 adsorption and desorption. Due to the volatilization of Zn, PCN‐224−ZnCo1‐950 has greatly improved basicity and suitable acidic/alkaline site concentration compared to the precursor. It can be efficiently used to carbon dioxide absorption and catalyze the cycloaddition of CO2 with epoxides.