Gibbs-Thomson mediated ice growth inhibition by MOF-based organic linkers through interfacial clustering

In this work, we present the first computational investigation of MOF organic linkers as small-molecule ice recrystallisation inhibition (IRI) agents. Guided by previous computational and experimental studies on MOF-based IRI agents, we selected four promising linker candidates: benzene-1,4-dicarboxylic acid (BDC) and its hydroxyl- and carboxyl-functionalized variants, alongside the 2,2'-bipyridine-5,5'-dicarboxylic acid (commonly known as BPYDC) linker. Density functional theory calculations confirmed their structural stability, and molecular dynamics (MD) simulations at 240 K validated their IRI activity. Notably, these molecules form interfacial clusters that adsorb onto the ice surface, exhibiting a pronounced concentration-dependent response. We observed an inverse relationship between the ice growth rate and molecular concentration. This trend is characterized by a critical threshold below which clusters are insufficient to inhibit growth, and a saturation point at higher concentrations, beyond which the inhibition efficiency plateaus. These findings are consistent with recent experimental reports. In the high-concentration regime, interfacial clustering induces curvature at the ice front, suppressing growth via the Gibbs-Thomson effect. MD simulations identified BPYDC as the most effective inhibitor. Further analysis revealed that the larger molecular size of BPYDC promotes the formation of larger interfacial clusters, enabling superior surface coverage and enhancing growth inhibition relative to BDC and its derivatives. Quantifying the thermal hysteresis induced by interfacial curvature reveals that linker clustering directly influences the magnitude of hysteresis, thereby explaining the observed ice growth behavior. This study provides the first direct molecular evidence that the efficacy of small-molecule IRIs is governed by interfacial clustering and surface coverage, rather than hydrogen bonding alone. By identifying a unique surface coverage threshold and saturation behavior of inhibition, we establish MOF linkers as a potent new class of IRI agents.