Anion Regulates scu Topological Porous Coordination Polymers into the Acetylene Trap

The development of efficient porous absorbents with high uptake and selectivity remains a great challenge, especially for the recovery of acetylene (C2H2) from its carbon dioxide (CO2)-containing mixtures. Here, we propose and report an anion-planting strategy for regulating the scu topological porous coordination polymers (PCPs) into the C2H2 trap. The three electronegative anions SiF62-, TiF62-, and ZrF62-, in addition to the ligand of 3,5-di(1H-imidazol-1-yl)benzoic acid (HL) and Cu2+ ion, were employed to construct highly porous PCPs (NTU-60, NTU-61, and NTU-62) with varied window aperture. Especially, due to a matching distance (d(F-F)) of 5.7 angstrom along the c-axis, the limited space that can be assigned as a single C2H2 trap enables NTU-61 to show optimal ability for C2H2 (van der Waals (vdW) parameters of the two H atoms: similar to 5.72 angstrom) recognition, validated by Grand Canonical Monte Carlo (GCMC) calculations and Raman spectra. These characteristics allow the NTU-series to show higher C2H2 uptake, as well as excellent C2H2/CO2 separation performance under dynamic conditions. The molecular insight and strategy here not only permit balanced adsorption and separation in a single domain but also exhibit an opportunity to develop advanced adsorbents in nearly all frameworks with lattice or coordinated ions, which may act as the platforms for various selective guest trappings with on-demand time and/or spatial resolution.

Automated summary

This study proposes an anion-planting strategy to regulate the porous coordination polymers for efficient separation and adsorption of acetylene. By introducing specific anions and ligands, porous polymers with different window apertures were constructed, and a structure with suitable matching distance was chosen to achieve high separation and adsorption of acetylene. This molecular insight and strategy offer a possibility for developing advanced adsorbents.