A bifunctional polycentric-affinity MOF/MXene heterojunction-based molecularly imprinted photoelectrochemical organophosphorus-sensing platform

Abstract

The analytical functionalization of metal organic frameworks (MOFs) has been an extremely attractive topic in photoelectrochemical (PEC) sensing. However, most PEC sensors based on photoactive MOFs are more focused on the acquisition and amplification of semiconductor photoelectric signals, and the study of affinity mechanisms for specific targets is more limited. Here, we find that PCN-224 (Zn) can effectively sense organophosphorus structures through a multicenter affinity mechanism, as evidenced by x-ray photoelectron spectroscopy (XPS) and computational chemistry. Further, we coupled PCN-224(Zn) to Nb4C3 to form a Schottky junction that enhances the photoelectric signal response of the sensor. In particular, the heterojunction exhibited a higher photocurrent density than pristine PCN-224(Zn) (17.3 μA vs. 26.5 μA cm−2). On the basis, we developed a novel MOF-based polycentric-affinity PEC sensing strategy for dimethoate (DIM) detection in concert with molecular imprinting technology. The affinity effects of the Lewis acidic center sites (Zn(II), Zr(IV)) and spatial matching through molecular imprinting synergistically ensure that DIM is precisely captured. Ultimately, a trace DIM-PEC sensor was constructed by a competitive strategy using dopamine as an electron donor. The photocurrent intensity was linearly related to the logarithm of DIM concentration in the range of 0.1 nM to 1000 nM, with a low detection limit of 26.1 pM (3σ/S). This study demonstrates the potential of bifunctional polycentric-affinity MOF in the PEC sensing.