Probing the Node Chemistry of a Metal–Organic Framework to Achieve Ultrahigh Hydrophobicity and Highly Efficient CO2/CH4 Separation

We demonstrate a novel microwave-assisted strategy to in situ functionalize the node chemistry of Zr-based metal–organic frameworks (Zr-MOFs) with a 2-aminobenzimidazole (2-AMI) agent. The novel strategy can concomitantly weaken the Lewis acidity of Zr6O8 nodes of Zr-MOFs through bonding with 2-AMI, contributing to admirable surface hydrophobicity with an ultrahigh water contact angle of 151.7° and enhanced stability. The successful coordination process was jointly verified by thermogravimetry analysis, 1H nuclear magnetic resonance spectroscopy , and X-ray photoelectron spectroscopy analyses. Meanwhile, the tailor-made pore microenvironment enabled highly efficient CO2/CH4 separation via a synergetic equilibrium-kinetic effect. Gas adsorption isotherms and time-dependent kinetic profiles cooperatively reveal that UiO-66(N10%-Zr) exhibits an advanced ideal adsorbed solution theory selectivity of 326, an excellent diffusion selectivity of 60.7, and a dynamic selectivity of 195 for CO2/CH4 separation, confirming the unwanted equilibrium-kinetic effect. Breakthrough experiments and modeling simulations further confirm the enhanced hydrophobic nature and high CO2/CH4 separation performance of UiO-66(N10%-Zr) even under humid conditions. The node-based engineering strategy is here demonstrated to be highly effective for CO2/CH4 separation, providing a new direction to achieve advanced MOF structures with sustainable advantages including high adsorption capacity, high selectivity, and hydrophobicity, which are of crucial significance for industrial applications.