Multifunctional lanthanide MOFs with active sites as new platforms for smart sensing of methylmalonic acid and anti-counterfeiting applications

Abstract

Insufficient intake of vitamin B₁₂ in humans can lead to the development of vitamin B₁₂ deficiency with involuntary movement disorders. In this work, a smartphone-enabled sensing platform was designed for early diagnosis of vitamin B₁₂ deficiency with involuntary movement disorders. Thus, a series of isostructural multifunctional lanthanide metal–organic frameworks (Ln-MOFs), {[Ln(L)(NMP)(H₂O)₃]·NMP·H₂O}_n (1-Ln, Ln = Eu, Tb, or Eu_xTb_1−x and NMP = 1-methyl-2-pyrrolidinone), were synthesized via 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H₃L) and Ln³⁺. 1-Ln exhibits a 4-linked two-dimensional (2D) structure with a parallel stacking and staggered arrangement between the layers, and a 3D supramolecular framework through hydrogen bonding. The fluorescence sensing studies demonstrate that 1-Eu exhibits high sensitivity and a low detection limit (1.07 × 10⁻⁵ M) for methylmalonic acid, a potential marker of vitamin B₁₂ deficiency in urine. On the other hand, the prepared fluorescent ink displays color tunability and good stability, indicating that 1-Ln is a new potential anti-counterfeiting material.