Functionalized fluorescent Zr-MOF based on photoinduced electron transfer for highly sensitive detection of nitroaromatic explosives

The development and construction of fluorescent sensors with high sensitivity for nitroaromatics explosives detection is of great significance for national security and public environmental issue. Herein, the mechanism of photoinduced electron transfer (PET) was utilized to design a newly amino-functionalized luminescent Zr-based metal-organic framework (NU-1000-NH2) for ultra-sensitive fluorescent detection of nitroaromatic explosives, like 2,4,6-trinitrotoluene, 2,4-dinitrotoluene and 2-nitrotoluene. The amino constructed in cavities of NU-1000-NH2 can be served as recognition site to capture and bind the nitroaromatic molecules. Thus the rational design of NU-1000-NH2 has been proven an effective route to recognize the electron-deficient nitroaromatic explosives, causing fluorescence quenching of NU-1000-NH2 due to the electron donor (–NH2)–acceptor (-NO2) interaction. Moreover, hydrogen-bonding effect of intermolecular N–H···Oanalyte between NU-1000-NH2 and analytes was also found assisting for binding and recognizing of nitroaromatic explosives molecule. And the density functional theory (DFT) calculations were conducted to further investigate and quantitatively assess the molecule orbitals (MOs), interaction energies and electrostatic potential map, revealing the electron transfer process from conduction band (CB) of MOF to LUMO of nitro analytes and stronger interaction effect was obtained with more nitro groups of NEs. This study provided a feasible idea to design functionalized fluorescent MOFs for nitroaromatic explosives sensing based on PET and hydrogen-bonding effect.