Tailoring Pore Environment of Metal–Organic Framework via In Situ Ligand Reaction Strategy to Boost CH 4 /N 2 Separation

Low-concentration coalbed gases are vital energy resources, but more significant amounts of N 2 severely limit the efficient utilization of their primary component CH 4 . Due to their similar physicochemical properties, separating CH 4 from N 2 remains highly challenging. Adsorption using porous materials has emerged as a promising approach for CH 4 /N 2 separation. Herein, we developed an in situ ligand reaction strategy to engineer the pore shape and chemical environment of a copper-based metal–organic framework (NUC-201Cu), achieving efficient CH 4 /N 2 mixture separation. Structural characterization elucidated the successful modulation of pore geometry and in situ conversion of CN groups into tetrazole groups during the one-spot MOF synthesis process. The single-component adsorption isotherm of NUC-201Cu exhibits a high CH 4 adsorption capacity of 36.4 cm 3 /g at 298 K and 1 bar, surpassing most reported MOFs for CH 4 /N 2 separation. Theoretical calculations unveiled that the suitable pore geometry and polarized tetrazole groups optimized pore environments to establish preferential interactions with CH 4 via C–H···N hydrogen bonds. In situ time-dependent infrared spectroscopy further confirmed the strong host–guest interaction between the framework and CH 4 . Breakthrough experiments verified the exceptional CH 4 /N 2 separation performance of NUC-201Cu under different dynamic separation processes. This research establishes an in situ ligand reaction strategy to optimize the pore adsorption environment for effective separation of CH 4 /N 2 .