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

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 CO2 capture capacity. Whereas the meso- and macro-pores present in NEU-2 are loaded with polietilenimina (PEI), micropores are maintained accessible for CO2 diffusion. Tests at different temperatures and cyclic adsorption-desorption experiments are performed to examine CO2 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 CO2 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 CO2‐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.