Ligand Symmetry Modulation for Designing Mixed-Ligand Metal–Organic Frameworks: Gas Sorption and Luminescence Sensing Properties

Herein, we report
the synthesis of a new mixed-linker Zn­(II)-based metal–organic
framework (MOF), {[Zn2(atz)2­(bpydb)]­(DMA)8}n (1) (atz = deprotonated
3-amino-1,2,4-triazole, bpydb = deprotonated 4,4′-(4,4′-bipyridine-2,6-diyl)
dibenzoic acid, DMA = N,N-dimethylacetamide),
through symmetry modulation of a triazole ligand. The desymmetrized
triazole linkers not only bond to the Zn­(II) ions to result in a new
helical Zn-triazolate chain building unit but also lead to the formation
of a highly porous framework (N2 uptake: 617 cm3/g; BET surface area: 2393 m2/g) with 1D helical channels.
The adsorption properties of desolved 1 were investigated
by H2, C2H2, CO2, and
CH4 sorption experiments, which showed that 1 exhibited high uptake capacity for H2 at 77 K and C2H2 around room temperature. More importantly, the
high C2H2 uptake capacity but low binding energy
makes this MOF a promising candidate for effective C2H2 capture from C2H2/CO2 and
C2H2/CH4 mixed gases with low regenerative
energy cost. In addition, 1 shows potential application
for the luminescence sensing of small aromatic molecules picric acid
(PA) and p-xylene (PX).