Programmable Guest‐Induced 5‐Phase‐Transition Topological Reconstructions of Cobalt Formate Metal–Organic Frameworks

Abstract

ABSTRACT Structural dynamics in metal–organic frameworks (MOFs) typically rely on elaborate, flexible organic linkers. Here, we challenge this paradigm by demonstrating a rare, reversible 5‐phase‐transition cycle in a minimalist cobalt formate MOF system. Central to this evolution is the conceptual reframing of the amorphous state (Co‐Amor); rather than representing a structural dead‐end, Co‐Amor functions as a programmable, high‐energy reactive hub that lowers reorganization barriers. We show that specific guest molecules selectively direct the reconstruction of this amorphous matrix into distinct crystalline architectures, including chiral (Co‐Hex), perovskite‐like (Co‐Trig), diamondoid (Co‐Mono1), and hydrated (Co‐Mono2) frameworks, effectively ‘reprogramming’ the material's underlying lattice physics. The generality of the guest‐molecule selectivity is verified by Co‐Hex and Co‐Trig, which have different crystalline structures but share the same phase‐transition behavior, thereby further highlighting the adaptability and importance of this system. Most notably, we uncover a rare gas‐solid reconstruction where CO2 acts as a morphogenic trigger, inducing a gradual amorphous‐to‐crystal transition to the rigid Co‐Mono1 phase. This chemoselectivity originates from a specific C–H···O hydrogen‐bond complementarity between the formate channel walls and CO2. This work highlights the untapped potential of amorphous intermediates in directing structural reconfigurations, offering a blueprint for designing highly adaptive materials from the simplest molecular building blocks.