Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework

Abstract

Efficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

Optimal Pore Chemistry in an Ultramicroporous Metal–Organic Framework for Benchmark Inverse CO2/C2H2 Separation

“…At 273 K, CO 2 and C 2 H 2 uptakes can reach 151.7 and 53.5 cm 3 cm −3 , respectively (Figure 2 b). The uptake of CO 2 at 298 K is much higher than that of the most state‐of‐the‐art CO 2 ‐selective materials, such as MUF‐16 (74.7 cm 3 cm −3 ), [2c] SIFSIX‐3‐Ni (98.4 cm 3 cm −3 ), [1d] PCP‐NH 2 ‐ipa (93.6 cm 3 cm −3 ), [17] and CD‐MOFs (60.4 cm 3 cm −3 ) [7] . At 273 K, the uptake is comparable with that of the benchmark Tm‐OH‐bdc (153 cm 3 cm −3 ) [18] (Figure 2 c), suggesting the feasibility of Ce IV ‐MIL‐140‐4F in inverse CO 2 /C 2 H 2 separation.…”

Photoinduced Electron‐Transfer (PIET) Strategy for Selective Adsorption of CO2 over C2H2 in a MOF

“…The observed CO 2 /C 2 H 2 uptake ratio measured at 100 kPa and 273 K may reach approximately 7.1, which is the second highest CO 2 /C 2 H 2 adsorption ratio in the known values (Table 1). [6o, 7b–e] Moreover, PMOF‐1 displays an unprecedented photocontrollable gate effect to CO 2 : the as‐synthesized sample exhibits a gate effect, which disappears after PIET.…”

“…However, Very few reported porous materials have better adsorption of CO 2 than C 2 H 2 at standard pressure due to the stronger interactions of C 2 H 2 with a sorbent (Table 1). [4, 6c,g–j,o, 7] In them, high CO 2 /C 2 H 2 uptake ratio with minor adsorption of C 2 H 2 was only unexpectedly observed in K 2 [Cr 3 O(OOCH) 6 (4‐ethylpyridine) 3 ] 2 [α‐SiW 12 O 40 ] (≈4.8 ratio), [6h] [Mn(bdc)(dpe)] (≈6.4 ratio), [6o] Cd‐NP (≈6.0 ratio) [7d] and MUF‐16 family (up to ≈12.0 ratio) [7e] . General design strategies for dominant adsorption of CO 2 over C 2 H 2 while keeping minor adsorption of C 2 H 2 are still absent.…”

Optimal Pore Chemistry in an Ultramicroporous Metal–Organic Framework for Benchmark Inverse CO2/C2H2 Separation

“…However, since CO 2 is the main contaminant in C 2 H 2 (3 % and even up to 50 %), [2e] CO 2 ‐selective sorbents are preferred for C 2 H 2 purification because they will permit the direct isolation of C 2 H 2 as a pure raffinate product. This will also efficiently leverage extensive industrial expertise in light‐product‐focused adsorptive cycles [1c, 2c] . Unfortunately, MOFs exhibiting inverse CO 2 /C 2 H 2 selectivity are rare, and within this subset of materials, the trade‐off between CO 2 adsorption capacity and inverse CO 2 /C 2 H 2 selectivity is still a significant barrier in prevailing materials.…”