MIL-91(Ti), a small pore metal–organic framework which fulfils several criteria: an upscaled green synthesis, excellent water stability, high CO2 selectivity and fast CO2 transport

Abstract

A multidisciplinary approach combining advanced experimental and modelling tools was undertaken to characterize the promises of a small-pore type Ti-based metal–organic framework, MIL-91(Ti) for CO₂ capture. This material was prepared using two synthesis strategies, i.e. under hydrothermal conditions and under reflux, and its single component adsorption behaviour with respect to CO₂, CH₄ and N₂ was first revealed by gravimetry measurements. This hydrophilic and highly water stable MOF is characterized by a relatively high CO₂ adsorption enthalpy. Molecular simulations combined with in situ powder X-ray diffraction evidenced that this is due to the combined interaction of this probe with N–H and P–O groups in the phosphonate linker. High CO₂ selectivities in the presence of either N₂ or CH₄ were also predicted and confirmed by co-adsorption measurements. The possibility to prepare this sample under reflux represents an environmentally friendly route which can easily be upscaled. This green synthesis route, excellent water stability, high selectivities and relatively fast transport kinetics of CO₂ are significant points rendering this sample of utmost interest for CO₂ capture.