at first, you should mentioned to sensor properties. which parameter are essential and important for a good sensor?

based on information about sensors, you can select MOFs.

the realm of MOFs are very huge and you can select best of them for your goal.

Metal Organic Frameworks (MOFs) are highly porous materials. The best thing about them is the ease of tailoring the pore size and functionalization of ligands. For getting specific metal sensor you need to design your ligand specifically which will help you to capture that specific metal ion from the solution. But while designing that you need to keep the porosity also. So, for designing the specific application MOF you need to take care many parameters, like porosity, dimensionality of MOFs, stability of MOFs in respective solution where you want to test it, ligand functinonalization.

For more insight you can go through our group recent article in Chem Eur J

where we rationally designed a bi-functional MOF for selective gas adsorption and aqueous phase TNP sensing

https://www.researchgate.net/publication/321108620_Frontispiece_Rational_Design_of_a_Bifunctional_Two-Fold_Interpenetrated_Zn_II_-Metal-Organic_Framework_for_Selective_Adsorption_of_CO_2_and_Efficient_Aqueous_Phase_Sensing_of_246-Trinitrophenol

https://www.researchgate.net/publication/319904937_Rational_design_of_bifunctional_2-fold_interpenetrated_ZnII-metal-organic_framework_for_selective_adsorption_of_CO2_and_efficient_aqueous_phase_sensing_of_246-trinitrophenol

The nature of the MOFs is important so as to avoid a breakdown of the MOFs in the process of application. MIL-100(Fe), MIL-101 are MOFs you can study to see if they suit your particular purpose.