A highly sensitive turn-on ratiometric luminescent probe based on postsynthetic modification of Tb3+@Cu-MOF for H2S detection

Abstract

The fabrication of luminescent materials with lanthanide cations encapsulated within MOF pores is currently of interest because luminescent materials are used in numerous applications. In this study, a distinctive strategy via postsynthetic modification (PSM) of a novel metal–organic framework [Cu(HCPOC)₂]_n (Cu1) (H₂CPOC = 5-(4′-carboxyphenoxy)nicotinic acid) and terbium ions (Tb³⁺) for sensing hydrogen sulfide (H₂S) is reported. The obtained composite Tb³⁺@Cu1 emits a weak typical Tb³⁺ ion emission and strong ligand-centred emission. Interestingly, H₂S, as a strong electron donor, can strongly enhance the luminescence of Tb³⁺ through its superior affinity for Cu²⁺ ions. The composite Tb³⁺@Cu1 was designed as a luminescent turn-on ratiometric probe for H₂S detection, showing high sensitivity and selectivity. The detection limit of Tb³⁺@Cu1 (1.20 μM) is far below that of Cu1 (13.25 μM). Moreover, a similar ligand, 5-(4′-carboxyphenyl)nicotinic acid (H₂CPC), was used to synthesize a fascinating structure, [Cu₅(CPC)₂(HCPC)₂(OH⁻)₄]_n (Cu2), which was quite similar to that of the famous semiconductor MoS₂, with the advantageous support of an organic linker between layers, and it showed a band gap of 2.45 eV.