Fast and reversible phase transition in hydrochromic lanthanide metal-organic frameworks towards sweat pores mapping and identification

Lanthanide metal-organic frameworks (Ln-MOFs) are one of ideal candidates for hydrochromic materials with smart response owing to their tunable structural property and wide photofunctional applications. However, the negative response time of the hydrochromic Ln-MOFs still brings in a huge challenge for the practical application. Here we report a novel hydrochromic Ln-MOF with markedly improved response time. By adjusting the water ligands, the emission color shows a reversible change between yellow and magenta due to the manipulation of the energy transfer between Tb3+ and Eu3+ ions. The hydrochromic Ln-MOFs can be employed in the sweat pores mapping and identification because of their superior sensitivity to the trace water molecules. Besides, we also gain a deep insight into the MOF structure evolution by density function theory (DFT) simulation. These results set up a deep understanding of phase-transition MOF and the internal energy transfer by establishing versatile lanthanide-doped systems.