Synthesis of a novel amorphous metal organic framework with hierarchical porosity for adsorptive gas separation

Abstract

A novel amorphous iron metal-organic framework (NEU-2 = Fe(BPDI)(Py) 2 , BPDI = N,N'bis(glycinyl)pyromellitic diimide; Py = pyridine) with multichannel pore systems is synthesized, and subsequently tested as class 1 sorbent by evaluating its CO 2 capture capacity. Whereas the meso- and macro-pores present in NEU-2 are loaded with polietilenimina (PEI), micropores are maintained accessible for CO 2 diffusion. Tests at different temperatures and cyclic adsorption-desorption experiments are performed to examine CO 2 uptake and amine efficiency evolution. Moreover, the diffusion resistance present within the pores of the material is measured by comparing the fast uptake at the beginning of the capture (pseudo-kinetic regime) to the slow uptake at the end of capture towards equilibrium (pseudo-diffusive regime). It is also reported a comparative study of the CO 2 capture capacity of amorphous NEU-2 and crystalline NEU-1c. This research demonstrates that the ordered crystalline state of MOFs is not a requirement for gas uptake, establishing novel amorphous MOFs with hierarchical porosity as promising materials for CO 2 ‐capture applications. It is evidenced that amorphous MOFs may facilitate a variety of chemical separations due to its framework flexibility and, ultimately, its guest-responsive capability. • Design, synthesis and structure elucidation of an amorphous iron MOF (NEU-2). • NEU-2 shows a hierarchical pore distribution. • Amorphous MOFs as efficient designs for gas uptake. • NEU-2 addresses the trade-off between amine loading and low access to amine sites.