A new yttrium‐based metal–organic framework for molecular sieving of propane from propylene with high propylene capacity

Abstract

Developing energy-efficient alternatives for propylene (C 3 H 6 ) and propane (C 3 H 8 ) separation is of great significance and challenge in the petrochemical industry. Herein, we report the rational design of a new yttrium-based ultramicroporous metal-organic framework (MOF) comprised of 12-connected hexanuclear [Y 6 (OH) 8 (COO) 12 ] 2À cluster and 5-(3,5-dicarboxybenzoylamino)isophthalic acid (H 4 dbai) with ftw topology. It possesses a suitable pore window size and a relatively large pore volume for molecular sieving separation of C 3 H 8 from C 3 H 6 with a high C 3 H 6 capacity. At 298 K and 100 kPa, the adsorption capacity of C 3 H 6 was 2.57 mmol/g, which is the highest among the reported C 3 H 6 /C 3 H 8 molecular sieving MOF adsorbents. The molecular simulation revealed that the steric hindrance effect together with the electrostatic interaction of the oxygen sites in the window resulted in the molecular sieving separation of C 3 H 6 /C 3 H 8 . The breakthrough experiments confirmed its excellent separation performance under dynamic conditions to produce high purity (97.1%) of C 3 H 6 with a working adsorption capacity of 1.75 mmol/g.

Molecular Sieving of Propylene from Propane in Metal–Organic Framework-Derived Ultramicroporous Carbon Adsorbents

“…Significantly, an unprecedented uptake ratio of C 3 H 6 /C 3 H 8 at 1.0 kPa up to 403 was achieved on C-CDMOF-2-700, superior to that of SCMS-0.2-800 (177) and Y-abtc (99), and outperforming all reported adsorbents (Figure d,f). The uptake ratio of C 3 H 6 /C 3 H 8 at 298 K and 100 kPa on C-CD-MOF-2-700 was calculated to be 15.2, still higher than Co–gallate (12.8) and HIAM-301 (10.5), only next to Y-dbai (25.7) . The ultrahigh IAST selectivity (>10 4 ) was also achieved, and the uncertainness may be caused by the negligible adsorption of C 3 H 8 .…”

“…C 3 H 8 eluted out immediately, indicating negligible retention in the column, followed by C 3 H 6 with a long retention time of 18 min g –1 (Figure d), equivalent to a dynamic uptake of 1.18 mmol g –1 , verifying the great potential of C-CDMOF-2-700 for molecular sieving separation of C 3 H 6 /C 3 H 8 . The dynamic adsorption uptake of C 3 H 6 on C-CDMOF-2-700 is also competitive, which is much higher than those of Co–gallate (0.98 mmol g –1 ) and KAUST-7 (0.65 mmol g –1 ) but lower than those of Y-abtc (1.26 mmol g –1 ), HIAM-301 (1.66 mmol g –1 ), and Y-dbai (1.61 mmol g –1 ) . Similar complete separation performance but with a shorter retention time of C 3 H 6 was also realized on C-CDMOF-1-600 (Figure S15a), which may be ascribed to the slower diffusion rate.…”

“…Remarkably, the optimal C-CDMOF-2-700 with the most appropriate pore size (5.0 Å) exhibited a high uptake of C 3 H 6 (1.97 mmol g –1 ) at 298 K and 1 bar together with a negligible uptake of C 3 H 8 (0.13 mmol g –1 ) under identical conditions, demonstrating the great potential in molecular sieving separation of C 3 H 6 /C 3 H 8 . This notable amount of C 3 H 6 is even higher than some top-performing molecular sieve adsorbents like KAUST-7 (1.41 mmol g –1 ), Co–gallate (1.79 mmol g –1 ), and Y-abtc (1.95 mmol g –1 ), only next to HIAM-301 (3.2 mmol g –1 ), Y-dbai (2.57 mmol g –1 ), and SCMS-0.2-800 (2.54 mmol g –1 ) (Table S4). The isosteric heat of adsorption ( Q st ) at zero coverage of C 3 H 6 based on the virial method (Table S4) was calculated to be 34.6 kJ mol –1 , significantly lower than other molecular sieve adsorbents, only slightly higher than that of the benchmark HIAM-301 (Figure c,e), indicating a facile regeneration under mild conditions.…”

Recent Advances in the Development of Metal–Organic Frameworks for Propylene and Propane Separation

“…Breakthrough experiments show that 99.5% pure C 3 H 6 can be separated from a C 3 H 6 /C 3 H 8 mixture. Besides, another isostructural material Y-dbai (H 4 dbai = 5-(3,5-dicarboxybenzoylamino)­isophthalic acid) similarly presents a strong sieving ability in C 3 H 6 /C 3 H 8 separation …”

“…Besides, another isostructural material Y-dbai (H 4 dbai = 5-(3,5dicarboxybenzoylamino)isophthalic acid) similarly presents a strong sieving ability in C 3 H 6 /C 3 H 8 separation. 93 The tradeoff between uptake capacity and separation selectivity is a long-lasting problem in gas separation. Interestingly, a newly reported ftw type MOF Y 6 (OH) 8 (eddi) 3 (DMA) 2 (also termed as HIAM-301; eddi = H 4 eddi = 5,5′-(ethene-1,2-diyl)diisophthalic acid) with a distorted pore structure (Figure 6c) has set a good example to overcome this dilemma.…”