Abstract
1) The article discusses the evolution of metal-organic frameworks (MOFs) from monometallic to bimetallic formulations, highlighting their improved tunability and synergistic effects for specific applications.
2) It emphasizes the stability of a Co/Tb-based BiM-MOF, which can measure pH levels in artificial gastric juices both in solution and on paper-based substrates, a feature not previously reported.
3) The paper introduces a paper-based and colorimetric device for detecting tetracycline (TC) using a bimetallic MOF (Gd@Eu), showcasing a visual fluorescence-based color tonality from blue to red.

Research Background
1) Industry Problems: The need for sensitive and stable biochemical sensors has increased, especially in areas like environmental monitoring and medical diagnostics.
2) Previous Solutions: Previous research has utilized monometallic MOFs for sensing applications, but they often lack the required stability and sensitivity.
3) Innovation: The authors propose the use of bimetallic MOFs (BiM-MOFs) for enhanced sensing capabilities, including improved stability and tunability.

Experimental Details
1) Preparation of BiM-MOF: The authors synthesized a stable Co/Tb-based BiM-MOF using a post-modification solvothermal method, functionalizing the surface with 1-hydroxypyrene (1-OHP).
2) pH Sensor Experiment: The BiM-MOF was tested for its ability to measure pH levels in various aqueous solutions, with fluorescence emission spectra recorded for solutions of different pH values.
3) Tetracyclin Detection: A paper-based device was created for the detection of tetracycline, combining two Ln-based MOFs to create a dual-emission ratio fluorescent probe.

Analysis and Tests
1) Fluorescence Emission Spectra: The BiM-MOF showed a characteristic fluorescence associated with Tb ions that changed with pH, used for creating a calibration curve.
2) Ratiometric Chromaticity Analysis: The change in fluorescence color from blue to green with pH elevation was used for visual determination of pH levels.
3) Long-Term Stability and Reproducibility: The paper-based pH microsensor demonstrated stability for at least one month and excellent reproducibility with a relative standard deviation (RSD) of less than 7.3%.

Conclusion
1) Enhanced Properties: BiM-MOFs have shown improved tunability and a broader range of properties for biochemical sensing applications.
2) New Opportunities: The introduction of a second metal into MOFs has created new opportunities for designing materials with unique physicochemical properties.
3) Challenges Ahead: Despite progress, BiM-MOF development faces challenges in achieving optimal synergy between metals and ensuring stability in various applications.
4) It is hoped that authors will conduct supplementary research on the mechanistic understanding of BiM-MOFs and their integration into existing sensing technologies.


Recent Advances of Bimetallic-Metal Organic Frameworks: Preparation, Properties, and Fluorescence-Based Biochemical Sensing Applications
Sameera Sh. Mohammed Ameen* and Khalid M. Omer*
DOI：10.1021/acsami.4c06931
Link：https://pubs.acs.org/doi/10.1021/acsami.4c06931