Carbon molecular sieve membranes derived from hydrogen-bonded organic frameworks for CO2/CH4 separation.

Carbon molecular sieve (CMS) membranes are ideal candidates for natural gas separation due to their rigid pore structures and stability. The chemical composite and spatial configuration of the used precursors for deriving CMS membranes can greatly influence the final microporous structure and separation performance of the membranes. Most CMS membranes are transformed from amorphous precursors such as polymers nowadays. Here, for the first time, we report a new type of CMS membrane derived from a crystalline porous hydrogen-bonded organic framework membrane (named HCMS). The conversion process has been studied with the characterization of TGA, FTIR, XRD, SEM, and pore size distribution. The effect of pyrolysis temperature on the membrane structure has been investigated to achieve optimized CO 2 /CH 4 separation performance. On the one hand, as the pyrolysis temperature increases from 550 to 650 °C, the pore size distribution of HCMS membrane is narrowed, which is conducive to improving the molecular sieving effect of the membrane. On the other hand, higher ratios of graphitic N and pyrrolic N, which show better affinity for CO 2 molecules than pyridinic N, are obtained on the HCMS membranes, leading to more favorable adsorption of CO 2. The optimized HCMS membrane pyrolyzed at 600 °C shows a remarkable CO 2 /CH 4 selectivity of 128 and excellent separation stability at varying temperatures and pressures. The HCMS membranes derived from the crystalline HOF precursor can also maintain a stable separation performance against physical aging. The results reported in this work may open the door to constructing CMS membranes with the precursor of crystalline porous membranes. Crystalline porous hydrogen-bonded organic framework membrane is employed as a new kind of precursor for the first time to derive carbon molecular sieve membrane with a narrow pore size distribution, which reveals good separation selectivity and stability for CO 2 /CH 4. [Display omitted] • For the first time, a HOF membrane is used as a precursor to derive HCMS membrane. • Ordered porosity of HOF leads to a narrow pore size distribution of HCMS membrane. • Effect of pyrolysis temperature on membrane structure and CO 2 affinity is studied. • The HCMS-600 membrane reveals the optimized CO 2 /CH 4 separation selectivity of 128. • The HCMS-600 membrane is long-term stable at variable temperatures and pressures. [ABSTRACT FROM AUTHOR]