Engineering bimetallic MOF nanosheets: post-modification strategy, antibacterial activity, and pollutant adsorption efficiency

Herein, Cu-based and Zn–Cu bimetallic metal–organic framework (MOF) nanosheets were synthesized and subsequently post-synthetically modified using 3-aminopropyltrimethoxysilane (APTMS). The obtained materials were characterized using FTIR, XRD, TEM, FE-SEM, and BET analyses. Their antibacterial activity and pollutant removal performance were subsequently evaluated, with Direct Red 23 (DR23) selected as the model contaminant. Inhibition-zone measurements confirmed the antibacterial activity of both Cu-BDC and Zn–Cu-BDC, which was attributed to the presence of Cu 2+ and Zn 2+ ions within the MOF structures. Increasing the adsorbent dosage enhanced dye removal efficiency because of the greater availability of active adsorption sites. The effect of pH on adsorption was examined at pH values of 2.1, 2.8, 6, 8, and 10, resulting in adsorption efficiencies of 92.1%, 48.8%, 45.6%, 44.9%, and 35.3% for Cu-BDC-NH₂ (CBN), and 94.7%, 49.6%, 43.5%, 42.1%, and 33.6% for Zn–Cu-BDC-NH₂ (ZCBN), respectively. The removal efficiencies at initial DR23 concentrations of 100, 150, 200, and 250 ppm were determined to be 92.1%, 66.8%, 54.8%, and 29.7% for CBN, and 94.7%, 76.4%, 45.2%, and 34.1% for ZCBN, respectively. At adsorbent dosages of 1, 2, 3, and 4 mg, the corresponding removal efficiencies were 58.4%, 61.8%, 92.1%, and 95.6% for CBN, and 43.3%, 50.8%, 94.7%, and 95.4% for ZCBN. Adsorption isotherm followed the Langmuir model exhibiting high correlation coefficients (R 2 = 0.9977 for CBN and R 2 = 0.9963 for ZCBN). Kinetic analysis indicated that DR23 adsorption obeyed the pseudo-second-order model. Furthermore, the materials exhibited excellent recyclability, with DR23 removal efficiencies after five cycles measured at 94.7%, 92%, 90%, 88%, and 85%, respectively.