Closed-pore crystal capable of adsorbing CO2 onto isolated cavities generated by disorderly mixing of substituents on host skeleton

A single crystal adsorbent, [Rh(II)(2)(bza)(4)(2,3-empyz)](n)(2,3-empyz = 2-ethyl-3-methylpyrazine) (1), was synthesized by self-assembly reaction of a Rh-2 benzoate complex and substituted pyrazine linker. The compound consists of one-dimensional zigzag chains, which generated a closed-pore structure without channels. The cavities were statistically generated by the static disorder of substituents on pyrazine and are separated by long intervals within the crystal. The property of CO2 absorption was characterized in this closed-pore system. The CO2 inclusion structure was determined by single-crystal X-ray diffraction measurements. These studies suggest that CO2 molecules were adsorbed and diffused in the nonporous crystal with the isolated cavities.