This work performs a systematic computational study toward a molecular understanding of the separation characteristics of metal-organic frameworks (MOFs), for which the purification of synthetic gas by two representative MOFs, MOF-5 and Cu-BTC, is adopted as an example. The simulations show that both geometry and pore size affect largely the separation efficiency, complex selectivity behaviors with different steps can occur in MOFs, and the electrostatic interactions that exist can enhance greatly the separation efficiency of gas mixtures composed of components with different chemistries. Furthermore, the macroscopic separation behaviors of the MOF materials are elucidated at a molecular level to give insight into the underlying mechanisms. The findings as well as the molecular-level elucidations provide useful microscopic information toward a complete understanding of the separation characteristics of MOFs that may lead to general design strategies for synthesizing new MOFs with tailored properties, as well as guiding their practical applications.

Current technologies for removing heavy metal ions are typically metal ion specific. Herein we report the development of a broad-spectrum heavy metal ion trap by incorporation of ethylenediaminetetraacetic acid into a robust metal-organic framework. The capture experiments for a total of 22 heavy metal ions, covering hard, soft, and borderline Lewis metal ions, show that the trap is very effective, with removal efficiencies of >99% for single-component adsorption, multi-component adsorption, or in breakthrough processes. The material can also serve as a host for metal ion loading with arbitrary selections of metal ion amounts/types with a controllable uptake ratio to prepare well-dispersed single or multiple metal catalysts. This is supported by the excellent performance of the prepared Pd2+-loaded composite toward the Suzuki coupling reaction. This work proposes a versatile heavy metal ion trap that may find applications in the fields of separation and catalysis.

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