Bulky substituent and solvent-induced alternative nodes for layered Cd–isophthalate/acylhydrazone frameworks

Abstract

A series of three cadmium-based two-dimensional (2D) metal–organic frameworks, featuring 4-pyridinecarboxaldehyde isonicotinoyl hydrazone bridging pillars (pcih) and either 5-tert-butyl-substituted or non-substituted isophthalate linkers, have been prepared and characterized. Isophthalates with bulky tert-butyl substituents (tBu-iso²⁻) form two-dimensional (2D) frameworks with various metal node nuclearities: [Cd(tBu-iso)(pcih)(DMF)]_n or [Cd₂(tBu-iso)₂(pcih)₂]_n, dependent on synthetic conditions; whereas, in contrast, unsubstituted isophthalates (iso²⁻) yield only the framework with dinuclear nodes [Cd₂(iso)₂(pcih)₂]_n, regardless of the conditions. Diverse nodes of interdigitated layers have a significant influence on the thermal stability and adsorption behavior of the materials.