CO2-generated amorphous metal organic frameworks for efficient CO2 conversion

Abstract

Developing a feasible method to capture and utilize post-combustion CO₂ in order to mitigate the adverse effects of excessive CO₂ emission is a challenging task. Herein, we demonstrate a series of newly fabricated CO₂-based metal–organic frameworks (MOFs) for CO₂ solidification and utilization. The CO₂ molecules react with deprotonated piperazine ligands, self-assemble with metal ions (Cu²⁺, Co²⁺) and generate a batch of MOFs with adjustable crystallinity from crystalline to amorphous. The crystalline MOFs can be precisely controlled by adjusting the ratio of metal sites, organic ligands and additional modulators through a bottom-up synthesis method. It is found that the amorphous CO₂-based MOFs show outstanding catalytic performance for CO₂ cycloaddition with epoxides (yield >99%, TOF = 218 h⁻¹) superior to that of the corresponding crystalline ones, which is attributed to the abundant catalytic sites and accessible hierarchical pores of amorphous MOFs.