Method of detecting mercury ions with a fluorescein hydrazide-appended metal-organic framework as a chemosensor

2:

• The method of claim 1, wherein a unit of the MOF chemosensor composite has a formula of [Ni3(BTC)2(H2O)3−n(FH)n] wherein n=1, 2 or 3.

3:

• The method of claim 1, wherein at least 90% of the nickel is Ni2+.

4:

• The method of claim 1, wherein the MOF chemosensor composite has a morphology of rod-shaped structures assembled into sheets.

5:

• The method of claim 1, wherein the MOF chemosensor composite has a Brunauer-Emmett-Teller (BET) specific surface area of 350-450 m2 g−1.

6:

• The method of claim 1, wherein the MOF chemosensor composite has a stability up to 150° C.

7:

• The method of claim 1, wherein the MOF has at least one pore;
• and
• wherein the fluorescein hydrazide at least partially penetrates at least one pore of the MOF.

8:

• The method of claim 1, further comprising:
• monitoring the change in the absorption profile of the MOF chemosensor composite between 350 and 600 nm;
• wherein a peak of the profile between 350 and 380 nm decreases in intensity and a peak between 550 and 600 nm increases in intensity in the presence of Hg2+.

9:

• The method of claim 1, further comprising:
• monitoring the change in the fluorescence profile of the MOF chemosensor composite between 500 and 650 nm;
• wherein a peak of the profile between 515 and 550 nm increases in intensity in the presence of Hg2+.

10:

• The method of claim 1, wherein the change in the absorption and/or fluorescence profile linearly correlates with the concentration of Hg2+ in the aqueous solution.

11:

• The method of claim 1, further comprising quantifying the change in the absorption and/or fluorescence profile to determine a concentration of Hg2+ ions in the aqueous solution.

12:

• The method of claim 1, wherein the aqueous solution further comprises at least one metal cation selected from the group consisting of Na+, K+, Ca2+, Mg2+, Sr2+, Rb2+, Cs2+, Al3+, Ga3+, Fe2+, Fe3+, Cu2+, Ni2+, Pb2+, Cd2+, Co2+, Zn2+, Pd2+, and Ag+;
• and
• the change in the absorption and/or fluorescence profile occurs only in the presence of Hg2+.

13:

• The method of claim 1, wherein the MOF chemosensor composite is selective for detecting Hg2+ ions.

14:

• The method of claim 1, wherein the limit of detection for Hg2+ ions is 1-10 ppb.

15:

• The method of claim 1, wherein the binding constant of the Hg2+ to the MOF chemosensor composite is 105-106 M−1.

16:

• The method of claim 1, further comprising:
• adding ethylenediaminetetraacetic acid to the mixture to form a solution;
• filtering the solution and drying at a temperature of 80-120° C. for at least one hour to form a recovered MOF chemosensor composite.

17:

• The method of claim 16, wherein the recovered MOF chemosensor composite maintains at least 90% of the crystallinity of the MOF chemosensor composite.