A facile fabrication of a multi-functional and hierarchical Zn-based MOF as an efficient catalyst for CO2 fixation at room-temperature

Abstract

Carboxyl-containing and amine-rich Zn-MOF [Zn₂L₂MA·2DMF] (MA = melamine, H₂L = 2,5-thiophenedicarboxylic acid) was facilely synthesized by a simple room-temperature stirring approach. In addition, the synthesis period was reduced to 2 h due to the organic amine of triethylamine (TEA), tripropylamine (TPA) or triamylamine (TAA) as a protonation agent, which made the fabrication of Zn-MOF both time- and energy-saving. The obtained Zn-MOF possessed hierarchical pores (labeled as Hie-Zn-MOF) and efficiently catalyzed the CO₂ fixation with epoxides. The existing mesopores in Hie-Zn-MOF were beneficial for the diffusion and accessibility of substrates as well as the carbonate product, while the micropores accelerated CO₂ gathering and strengthened its interaction with active sites. Hie-Zn-MOF-TEA with TEA as a protonation agent exhibited 97% yield of propene carbonate at room temperature. In particular, the catalytic activity for bulky epoxides was evidently higher than that for comparative Zn-MOF with only micropores (labeled as Mic-Zn-MOF), and the corresponding product yield was obviously improved from 64% to 88% with the butyl glycidyl ether substrate. Besides, the tentative synthesis procedure for the Hie-Zn-MOF catalyst and the feasible catalytic mechanism for CO₂ fixation to epoxides are proposed. The time- and energy-saving synthesis strategy and efficient Zn-MOF catalyst are attractive in CO₂ capture and CO₂ chemical conversion.