An Uncommon Carboxyl-Decorated Metal-Organic Framework with Selective Gas Adsorption and Catalytic Conversion of CO2

Abstract

A new three-dimensional (3D) framework, [Ni(btzip)(H₂ btzip)]⋅2 DMF⋅2 H₂ O (1) (H₂ btzip=4,6-bis(triazol-1-yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of nickel wire and a triazolyl-carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO₂ and C₂ H₆ adsorption capacity but also significant selective capture for CO₂ and C₂ H₆ over CH₄ and CO in 273-333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO₂ - and C₂ H₆ -philic sites. As a result of the presence of accessible Brønsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO₂ with propylene oxide/4-chloromethyl-1,3-dioxolan-2-one/3-butoxy-1,2-epoxypropane into cyclic carbonates.

Keywords: CO2 capture and conversion; crystal engineering; crystal structures; metal-organic frameworks; microporous materials.