Unveiling Novel Polymorphs of Zirconium-Based Metal–Organic\nFrameworks from De Novo Syntheses and Phase Transformations

Polymorphism\ngrants metal–organic frameworks (MOFs) a high\ndegree of structural diversity for various applications. Here, we\ndescribe the discovery of three new phases of zirconium-muconate MOFs,\ndenoted as NU-412 (<b>bct</b>), NU-413 (<b>bcu</b>), and\nNU-414 (<b>reo</b>). NU-412 was first synthesized using formic\nacid as both modulator and coligand de novo and was crystallographically\ncharacterized. The formate coligand in NU-412 could be selectively\nremoved to yield NU-413 with a higher degree of coordinative unsaturation\nat the Zr<sub>6</sub> node and maintained the channel geometry of\nthe structure. Inspired by the intermediate NU-414 product observed\nduring the growth of NU-412, we investigated the possibility of phase\ntransformations as an approach to yield NU-412 and demonstrated success\nin accessing novel polymorphs from existing phases.