Engineering cost-effective N-rich metal–organic frameworks (MOFs) for highly efficient CO2 capture and its catalytic conversion to cyclic carbonates: a step towards sustainable carbon utilization

Abstract

In an era where the optimization of CO₂ stands at the frontier of sustainable chemistry, we unveil two architecturally rare, N-rich metal–organic frameworks (MOFs), {[Zn₂(TATAB)₂(Me₃NH)₂](H₂O)₂(CH₃OH)₂}_n (ZS-2) and {[Cu₂(TATAB)₂(Me₃NH)₂](Me₂NCHO)₂}_n (ZS-3), meticulously designed using a solvothermal route. These crystalline frameworks manifest a unique srs topology (3/10/c1 net), elevating them beyond the realm of conventional porous materials. BET analyses reveal remarkably high surface areas, with ZS-2 exhibiting 630.35 m² g⁻¹ and ZS-3 reaching 641.36 m² g⁻¹, together with narrow pore-limiting diameters of approximately 2.40 nm and 3.98 nm, respectively. These features underscore their mesoporous nature, rendering them highly suitable for selective molecular sieving and effective CO₂ capture and fixation. ZS-3 shows a high CO₂ uptake of 64 cm³ g⁻¹, exceeding both ZS-2 (56 cm³ g⁻¹) and many benchmark MOFs reported in the literature. XPS analysis confirms strong metal–CO₂ interactions, as reflected by clear shifts in binding energies from 1022.08 to 1023.52 eV for Zn 2p and from 933.60 to 934.34 eV for Cu 2p, indicating strong chemisorptive affinity. Interestingly, ZS-2 exhibits better catalytic performance, with higher conversion efficiency, greater selectivity, and increased TON and TOF in CO₂-epoxide cycloaddition under mild conditions at 1 atm and 60 °C. The captured CO₂ was successfully converted into cyclic carbonates, as confirmed by ¹H NMR spectroscopy.