Metal-dependent adsorption and photothermal-assisted catalysis in heterometallic metal-organic frameworks

Abstract

The modular nature of metal-organic frameworks (MOFs) enables structural and functional tuning through controlled combinations of organic linkers and metal ions. Here, we report an isostructural MOF series, M-DGIST-20, constructed from trinuclear TiM2(mu 3-O)(COO)6 (M2+ = Ni2+, Co2+, and Mn2+) clusters and a naphthalenediimide-based ligand. The frameworks feature high porosity (approximate to 85% void volume) and serve as a platform to examine composition-function relationships. Iodine adsorption experiments reveal metal-dependent kinetics, with Ni-DGIST-20 showing the fastest uptake due to stronger M-I2 interactions and higher structural robustness. Post-synthetic coordination of imidazole at open metal sites further increases the adsorption rate and capacity. In addition, efficient photothermal conversion and accessible metal sites in M-DGIST-20 allow localized heating and Lewis acidic catalysis, accelerating the Knoevenagel condensation and subsequent Michael addition-intramolecular cyclization. This study demonstrates how compositional and post-synthetic tuning can modulate adsorption and catalytic activity of MOFs.