Acid-directed synthesis of three Cd-based metal–organic frameworks with luminescence and catalytic CO2 transformation properties

Abstract

In this paper, we showed an example of acid-directed hydrothermal synthesis of three Cd-based metal–organic frameworks (MOFs) under similar conditions, namely, [Cd(TIDB)(AA)_0.5(NO₃)]_n (1), [Cd₃(TIDB)₂(AA)₂(H₂O)₂(HCOO)₂]_n (2), and {[Cd₄(TIDB)(AA)₄(H₂O)₅](C₂H₅OH)₂(H₂O)₂}_n (3) (TIDB = 1,3,5-tri(1H-imidazol-1-yl)benzene, H₂AA = anthracene-9,10-dicarboxylic acid). Compound 1 was synthesized by the introduction of HNO₃ as a structure-directing agent. It has 2D coordination networks with the 3,4-c bey topology. The porous 3D supramolecular framework in compound 1 is stabilized by H-bonds. Compound 2 was formed with the use of a HCOOH agent. It has a 3D coordination network with a new 3,4,5-c underlying net topology, and it is also porous. Compound 3 was obtained using a CH₃COOH agent. It has a disordered non-porous 3D coordination network. Because 3 was hard to purify, 1 and 2 were chosen for further property investigation. On the one hand, fluorescence studies showed that 1 and 2 are both blue-emitting MOFs with quantum yields of 2.3% and 0.8%, respectively. On the other hand, CO₂ cycloaddition performance was also tested, which revealed that 2 has a superior catalytic conversion of epoxybutane at 60 °C and 1 atm with a high yield of up to 95.6%.