Isophthalate–Hydrazone 2D Zinc–Organic Framework: Crystal Structure, Selective Adsorption, and Tuning of Mechanochemical Synthetic Conditions

A new layered mixed-linker
metal–organic framework [Zn2(iso)2(pcih)2]n (MOF) built from isophthalate
ions (iso2–) and 4-pyridinecarbaldehyde isonicotinoyl
hydrazone (pcih) was prepared
using both solution and mechanochemical methods. By use of the latter,
the 2D MOF is obtained either in a one-mortar three-component grinding
or on the way of a two-step mechanosynthesis. Tuning of mechanochemical
synthetic conditions allowed us to identify both necessary and favorable
factors for the solid-state formation of the MOF. Single-crystal X-ray
diffraction reveals the presence of interdigitated layers in the ABAB
arrangement and interlayer 0D cavities filled with guest molecules.
Upon thermal activation, the dynamic framework exhibits stepwise and
selective adsorption of CO2 over N2 as well
as high-pressure H2 adsorption reaching maximum excess
of 1.15 wt% at 77 K. The mechanochemical synthetic protocol is expanded
to a few other interdigitated structures.