Isolation of CO 2 from acetylene (C 2 H 2 )v ia CO 2selective sorbents is an energy-efficient technology for C 2 H 2 purification, but as trategic challenge due to their similar physicochemical properties.T here is still no specific methodology for constructing sorbents that preferentially trap CO 2 over C 2 H 2 .W ereport an effective strategy to construct optimal pore chemistry in aC e IV -based ultramicroporous metalorganic framework Ce IV -MIL-140-4F,based on charge-transfer effects,f or efficient inverse CO 2 /C 2 H 2 separation. The ligandto-metal cluster charge transfer is facilitated by Ce IV with lowlying unoccupied 4f orbitals and electron-withdrawing Fatoms functionalizedt etrafluoroterephthalate,a ffording ap erfect pore environment to matchCO 2 .The exceptional CO 2 uptake (151.7 cm 3 cm À3 )along with remarkable separation selectivities (above4 0) set an ew benchmark for inverse CO 2 /C 2 H 2 separation, which is verified via simulated and experimental breakthrough experiments.The unique CO 2 recognition mechanism is further unveiled by in situ powder X-ray diffraction experiments,F ourier-transform infrared spectroscopym easurements,and molecular calculations.

Membrane technology is attractive for natural gas separation (removing CO2, H2O, and hydrocarbons from CH4) because of membranes’ low energy consumption and small environmental footprint. Compared to polymeric membranes, microporous inorganic membranes such as silicoaluminophosphate-34 (SAPO-34) membrane can retain their separation performance under conditions close to industrial requirements. However, moisture and hydrocarbons in natural gas can be strongly adsorbed in the pores of those membranes, thereby reducing the membrane separation performance. Herein, we report the fabrication of a polycrystalline MIL-160 membrane on an Al2O3 substrate by in situ hydrothermal synthesis. The MIL-160 membrane with a thickness of ca. 3 μm shows a remarkable molecular sieving effect in gas separation. Besides, the pore size and environment of the MIL-160 membrane can be precisely controlled using reticular chemistry by regulating the size and functionality of the ligand. Interestingly, the more polar fluorine-functionalized multivariate MIL-160/CAU-10-F membrane exhibits a 10.7% increase in selectivity for CO2/CH4 separation and a 31.2% increase in CO2 permeance compared to those of the MIL-160 membrane. In addition, hydrophobic MIL-160 membranes and MIL-160/CAU-10-F membranes are more resistant to water vapor and hydrocarbons than the hydrophilic SAPO-34 membranes.

Rational design of covalent organic frameworks (COFs) to broaden their diversity is highly desirable but challenging due to the limited, expensive, and complex building blocks, especially compared with other easily available porous materials. In this work, we fabricated two novel bioinspired COFs, namely, NUS-71 and NUS-72, using reticular chemistry with ellagic acid and triboronic acid-based building blocks. Both COFs with AB stacking mode exhibit high acetylene (C2H2) adsorption capacity and excellent separation performance for C2H2/CO2 mixtures, which is significant but rarely explored using COFs. The impressive affinities for C2H2 appear to be related to the sandwich structure formed by C2H2 and the host framework via multiple host–guest interactions. This work not only represents a new avenue for the construction of low-cost COFs but also expands the variety of the COF family using natural biochemicals as building blocks for broad application.

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