Mechanochemical Solid Form Screening of Zeolitic Imidazolate Frameworks using Structure-Directing Liquid Additives

We demonstrate a systematic application of the mechanochemical liquid-assisted grinding (LAG) methodology to screen for forms of zinc imidazolate (ZnIm2), of fundamental importance as the simplest member of the zeolitic imidazolate framework materials family. The exploration of 45 different liquid additives, selected based on their molecular structure and physicochemical properties has resulted in seven different ZnIm2 topologies, appearing in 12 structurally distinct solid forms (including two previously unknown forms of the crb (BCT) topology), amorphous phases, and the interrupted moc topology material. All prepared topologies were also explored computationally, using dispersion-corrected periodic density functional theory (DFT) calculations, enabling the rationalization of screening outcomes, and setting the stage for future prediction of additive-directed MOF synthesis. This first systematic exploration of LAG in screening for three-dimensional metal-organic frameworks demonstrates the potential of the liquid additive to not only accelerate materials synthesis, but also to direct it towards topologically different frameworks. The ability to discover novel forms in a material that already exhibits at least 21 crystalographically and functionally different forms provides a strong testimony on the power of mechanochemistry in metal-organic materials discovery.