Thermoregulated Phase‐Transition Synthesis of Two‐Dimensional Carbon Nanoplates Rich in sp2 Carbon and Unimodal Ultramicropores for Kinetic Gas Separation

The development of highly selective, chemically stable and moisture‐resistant adsorbents is a key milestone for gas separation. Porous carbons featured with random orientation and cross‐linking of turbostratic nanodomains usually have a wide distribution of micropores. Here we have developed a thermoregulated phase‐transition‐assisted synthesis of carbon nanoplates with more than 80 % sp² carbon, unimodal ultramicropore and a controllable thickness. The thin structure allows oriented growth of carbon crystallites, and stacking of crystallites in nearly parallel orientation are responsible for the single size of the micropores. When used for gas separation from CH₄, carbon nanoplates exhibit high uptakes (5.2, 5.3 and 5.1 mmol g^?1) and selectivities (7, 71 and 386) for CO₂, C₂H₆ and C₃H₈ under ambient conditions. The dynamic adsorption capacities are close to equilibrium uptakes of single components, further demonstrating superiority of carbon nanoplates in terms of selectivity and sorption kinetics.     

Low-Concentration C2H6 Capture Enabled by Size Matching in the Ultramicropore

Low-concentration ethane capture is crucial for environmental protection and natural gas purification. The ideal physisorbent with strong C₂H₆ interaction and large C₂H₆ uptake at low-concentration level has rarely been reported, due to the large pK_a value and small quadrupole moment of C₂H₆. Herein, we demonstrate the perfectly size matching between the ultramicropore (pore size of 4.6 Å) and ethane (kinetic diameter of 4.4 Å) in a nickel pyridine-4-carboxylate metal–organic framework (IISERP-MOF 2 ), which enables the record-breaking performance for low concentration C₂H₆ capture. IISERP-MOF 2 exhibits the large C₂H₆ adsorption enthalpy of 56.7 kJ/mol, and record-high C₂H₆ uptake at low pressure of 0.01–0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C₂H₆-loading crystal structure analysis revealed that the maximized interaction sites in IISERP-MOF 2 with ethane molecule originates the strong C₂H₆ adsorption. The dynamic breakthrough experiments for gas mixtures of C₂H₆/N₂(1/999, v/v) and C₂H₆/CH₄ (5/95, v/v) proved the excellent low-concentration C₂H₆ capture performance.