Abstract
<jats:p>Size-dependent phenomena appear across materials science, from quantum-confined semiconductor nanocrystals to size-tunable catalytic metals. Metal-organic frameworks (MOFs), a compositionally diverse class of porous coordination materials composed of metal nodes and organic linkers, are no exception. Despite the long-standing view of MOFs as bulk crystalline solids defined by their periodic lattice, a growing body of evidence demonstrates that MOF properties such as optical behavior, electronic structure, phase transition, mechanical flexibility, and adsorption characteristics depend markedly on particle size. Here, we report recent findings on size-dependent phenomena of MOF nanoparticles and emerging evidence that their metal-ligand bonds become more labile at smaller dimensions, offering a unifying explanation for the diverse size effects observed across this class of materials.</jats:p>