The impact of solution vs. slurry vs. mechanochemical syntheses upon the sorption performance of a 2D switching coordination network

The selection and optimization of synthesis routes for porous metal-organic materials are critical for their large-scale manufacture but remain largely underexplored. In this study, we compare mechanochemistry vs. slurry vs. solution methods for the synthesis of a 1D chain coordination polymer {[Co(bpy)(NCS)₂(H₂O)₂]·bpy}_n (chn-1-Co-NCS-H₂O) that is an intermediate to the 2D switching coordination network [Co(bpy)₂(NCS)₂]_n, sql-1-Co-NCS (1 = bpy = 4,4′-bipyridine). Although neat mechanosynthesis using Co(NCS)₂ and bpy as the starting materials failed, both water slurry and water-assisted mechanochemical syntheses afforded the desired intermediate, chn-1-Co-NCS-H₂O, in high yield. Nevertheless, the resulting sql-1-Co-NCS products were observed to exhibit different CO₂ sorption profiles depending on the synthesis methods used to prepare chn-1-Co-NCS-H₂O. This study reveals that water can play an important role in mechanosynthesis, not only by inducing and accelerating the reaction process, but also by enhancing product quality in a manner that is not readily detectable by PXRD.