Dual Site Lewis‐Acid Metal‐Organic Framework Catalysts for CO2 Fixation: Counteracting Effects of Node Connectivity, Defects and Linker Metalation. Issue 16 (4th July 2018)

• Record Type: Journal Article
• Authors: Epp, Konstantin; Semrau, A. Lisa; Cokoja, Mirza; Fischer, Roland A.
• Is Part Of: ChemCatChem. Volume 10:Issue 16(2018)
• Page Start: 3506
• Page End: 3512
• Publication Date: 2018-07-04
• Subjects: metal-organic frameworks -- heterogeneous catalysis -- carbon dioxide fixation -- Lewis acids -- porphyrinoids; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201800336
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Three Zr‐oxo‐cluster node and porphyrin‐linker based MOFs, MOF‐525, PCN‐222 and PCN‐224 exhibiting different linker connectivities of 12, 8 and 6 and their porphyrin‐linker metalated analogues, were synthesized and tested as catalysts for CO2 fixation by using the cycloaddition of CO2 and propylene oxide to propylene carbonate as the test reaction. In general, the catalytic activity correlates with the connectivity of the Zr‐oxo nodes. The lowest connected PCN‐224 (6‐fold) exhibits a superior catalytic activity in this series, while higher connected PCN‐222 (8‐fold) and MOF‐525 (12‐fold) are less active. Interestingly, the catalytic activity of the higher connected MOFs significantly depends on defects. The (ideally) 12‐connected MOF‐525, however exhibiting 16% of missing linker defects, features a higher catalytic activity compared to the 8‐connected PCN‐222 with less defects. The overall catalytic activity is increased in dual site catalysts when the porphyrin linkers are metalated with Mn(III) and Zn(II) centers, which are acting as additional Lewis acid sites. Here, the metalated MOFs with higher connectivity exhibit the highest activity. Abstract : Two Lewis acids for one job : The catalytic activity of Zr6 ‐nodes in Zr‐porphyrin MOFs in the cycloaddition of CO2 and propylene oxide depends on the tunable degree of connectivity of the nodes in the framework. The activity is further improved by the incorporation of Mn(III) sites, which shows the flexibility and variability potential of MOFs in catalysis.