Microstructural optimization of NH2-MIL-125 membranes with superior H-2/CO2 separation performance by innovating metal sources and heating modes

Abstract

Metal-organic framework (MOF) membranes have received increasing attention due to their unprecedented potential for energy-efficient gas separation. Compared with other MOF materials (like ZIF), fabrication and microstructural manipulation of high-performance Ti-MOF-based membranes, although being very attractive due to their excellent chemical and thermal stability, remained relatively less investigated due to the limitations of available titanium sources and heating modes. In this study, different Ti sources (TPOT, TiS2, and MXene) and heating modes (conventional heating, multi-mode microwave heating, and single-mode microwave heating) were examined for the preparation of NH2-MIL-125 membranes showing diverse microstructures and gas separation performances. The present work revealed that for the first time, MXene, the new two-dimensional Ti carbide, could be used as Ti source for synthesizing MOF membranes. The best performing NH2-MIL-125 membranes, which were obtained with TiS2 as the metal source under single-mode microwave heating, exhibited the highest H-2/CO2 selectivity (ca. 17.2) as well as considerable H-2 permeance (1.7 x 10(-7) mol m(-2) s(-1) Pa-1), owing to an enhanced non-thermal effect of single-mode microwave heating and balanced dissolution rate of TiS2.