Design of a Zn-MOF biosensor via a ligand "lock" for the recognition and distinction of S-containing amino acids.

Two new 2D Zn(ii) metal-organic frameworks (MOFs) {[Zn2(L)2(µ2-O)(H2O)3]·3DMA}n (Zn-1) and [Zn2(L)2(2,2'-bipy)(µ2-O)(H2O)2]n (Zn-2) (H2L = 2,5-thiophene dicarboxylic acid, bipy = 2,2'-dipyridyl) were designed and synthesized. Through the strategy of introducing bipy as a "lock", Zn-1 was transferred to Zn-2via a crystal-to-crystal process, which showed significantly enhanced solvent and air stability compared to that of Zn-1. Without post modification, Zn-2 was used as an electrode modified material to construct sensors for the electrochemical recognition and distinction of S-containing amino acids, including l-cysteine, l-methionine and l-cystine.