LPE-Grown Lanthanide-MOF/Cellulose Paper for Visual Sensing and Selective Dye Removal

Cellulose-based functional materials have attracted increasing attention for portable environmental monitoring and pollutant management; however, achieving a robust integration of functional components with cellulose substrates remains challenging due to weak interfacial adhesion and instability of conventional coating strategies. Herein, a binder-free liquid-phase epitaxy (LPE) strategy was developed to construct lanthanide metal-organic framework (Ln-MOF) coatings directly on unmodified cellulose fibers, yielding a stable and multifunctional Ln-MOF/cellulose composite material. The LPE process enabled uniform growth of Ln-MOF layers on cellulose paper, resulting in homogeneous luminescence with relative standard deviations below 2% and stable fluorescence performance over a wide pH range of 3-11. By regulating the Eu³⁺/Tb³⁺ ratio, the obtained composite paper exhibited tunable dual-emission characteristics and enabled smartphone-assisted ratiometric visualization of dipicolinic acid (DPA), a representative biomarker of bacterial spores, with a linear response range of 0-2000 μM and a detection limit of 10 μM. Furthermore, the anionic Ln-MOF coating endowed the cellulose material with charge-selective adsorption capability, allowing efficient removal of cationic dyes while maintaining structural integrity after four regeneration cycles. The applicability of the LPE strategy was further demonstrated using different lanthanide-organic linker systems. This work provides a versatile approach for fabricating stable cellulose/MOF composite materials and highlights their potential applications in portable chemical sensing and selective water purification.