Gallate-Based Metal-Organic Frameworks for Highly Efficient Removal of Trace Propyne from Propylene

Purification of propylene from the propyne (C3H4)/propylene (C3H6) mixture is a significant and challenging process in the chemical industry. Nowadays, the removal of propyne from propylene mainly relies on the energy-intensive hydrogenation catalyzed by noble metals. We herein report three gallate-based metal-organic frameworks, namely, M(II)-gallate (M = Ni, Mg, Co), which provide excellent performance in terms of removing propyne from the propyne/propylene mixture (1:99, v/v). The C3H4 uptake capacities of Mg-, Co-, and Ni-gallate can reach 3.75, 3.21, and 2.65 mmol/g, while the C3H6 uptake capacities are only 1.50, 1.49, and 0.9 mmol/g respectively, at ambient conditions. Particularly, the productivities of 99.9999% pure C3H6 in Co-gallate and Mg-gallate were 1580 and 1420 mL/g, respectively, outperforming the state-of-the-art material USTA-200 (1400 mL/g). The adsorption mechanism was further investigated by using the first-principle dispersion-corrected density functional theory calculations, revealing that the excellent C3H4/C3H6 separation ability of M-gallate originates from stronger supramolecular interactions and C-H-O interactions between the hydrogen atoms from C3H4 and oxygen atoms from M-gallate frameworks. Besides, the M-gallate materials also show excellent regeneration ability. Thus, this work demonstrates that the family of M-gallate materials shows industrially promising porous materials for propylene purification by the adsorption process.