Confined construction of CDs@MIL-101 as reusable and turn-on fluorescence sensor for highly sensitive water detection based on adsorption-solvent synergistic mechanism

Fabrication a reusable and highly sensitive fluorescence sensor in a controllable manner for water detection in solvents and humidity remains a top priority target yet a challenging task. In this work, carbon dots (CDs) are successfully implanted into confined metal–organic framework MIL-101(Cr) cages via "ship in the bottle" strategy and the confined CDs are firstly observed in MIL-101(Cr) cage showing high dispersion and high N content by advanced iDPC STEM technique. The highly selective water capture and sensitive changes of the fluorescence property with solution polarity and hydrogen-bonding donor acidity efficiently enhance the detection sensitivity and realize reusable turn-on detection based on the adsorption-solvent synergistic mechanism. Consequently, CDs@MIL-101 exhibits high sensitivity (detection limit: 0.036% and 0.028% v/v), wide response range (0.04–100% and 0.03–45%) and reusable stability for liquid water detection in acetone and tetrahydrofuran, respectively. Meanwhile, it can also detect gaseous water and the detection range is 23% to 85%. The analysis of real samples confirms the proposed method. Such construction strategy and detection mechanism will offer guidance for optimizing and expanding the detection performance of CDs, which is of great significance in the design and construction of novel multiphase sensors.