High-Pressure Carbon Dioxide Adsorption and Dynamic Breathing Behavior in a Flexible Zn2L2 Metallosupramolecular Mesocate

Abstract A discrete M2L2 metallosupramolecular complex containing bis-bidentate pyridylimine Schiff base ligand (L), [Zn2(NCSe)4(L)2]·5MeOH (1), has been synthesized and characterized. The solid-state structure of 1 reveals a neutral double-strand dinuclear mesocate architecture, comprising two Zn(II) atoms in octahedral geometry that coordinate with two chelating ligands L positioned in a side-by-side arrangement. Complex 1 demonstrates stability in water and a variety of common organic solvents, maintaining a pH range from 3 to 13, and can endure temperatures up to 240 °C. The thermally activated 1 has been examined for CO2 adsorption at pressures up to 20 bar and temperatures ranging from 0 to 55 °C, showing notable CO2 adsorption characteristics affected by temperature-dependent sorption hysteresis. The binding mechanism of the CO2-mesocate complex 1 was examined via in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at pressures up to 20 bar and a temperature of 35 °C. Notably, Hirshfeld surface analysis is employed to visualize and quantify intermolecular interactions, aiding in the identification and examination of active sites for the CO2 molecule. This study demonstrates the effectiveness of a supramolecular CO2 adsorption approach, utilizing flexible and low-symmetry mesocate components. The development of advanced carbon capture materials for both low- and high-pressure applications may benefit from this potentially promising approach.