Enhanced Enantioselective\nSensing of 1,1′-Bi-2-naphthol\nand Mandelic Acid by Proportional Fluorescence Sensor 3DOM Zn-MOF-74‑l‑Trp with Hierarchical Macro–Micropore Structure

The enantioselective performance of porous chiral metal–organic\nframeworks (CMOFs) is closely related to the pore size and uniformity\nof easily accessible active sites. The chiral recognition efficiency\nof microporous CMOFs is hindered by the restricted diffusion of the\nguest. Hierarchical porous chiral CMOFs with multiple pore size regimes\nranging from micropores to macropores have emerged as potential candidates\nin chiral separation applications. 3DOM Zn-MOF-74 crystalline porous\nmaterial with ordered macro–micropore structure was prepared\nwith a general bottom-up strategy by carrying out the controllable\nconfined growth of Zn-MOF-74 precursor in a removable three-dimensional\nordered macroporous (3DOM) polystyrene (PS) template. Then l-tryptophan ( l -Trp) was introduced into MOFs by the strategy\nof postsynthetic modifications, and finally, a chiral hierarchical\nporous functional material 3DOM Zn-MOF-74-l-Trp was successfully\nfabricated. Based on the two luminescent centers from the achiral\nligand H<sub>4</sub>DOBC and chiral ligand l-Trp, the proportional\nfluorescence sensor 3DOM Zn-MOF-74-l-Trp was hopeful to be\napplied in the field of enantioselective fluorescence sensing. The\nenantioselectivity factor values of microporous M-Zn-MOF-74-l-Trp for 1,1′-bi-2-naphthol (Binol) and mandelic acid (MA)\nwere 1.08 and 1.12, respectively. In comparison, the construction\nof hierarchical porous structure greatly enhanced the chiral recognition\nperformance, which may be due to the improved mass-transfer efficiency\nof chiral guest molecules and highly swelled accessibility to the\nchiral recognition sites in this CMOF composite, making the enantioselectivity\nfactor values correspondingly increased to 1.29 and 2.26, respectively.