BMA porous microspheres loaded with silane-modified Cu/Ni@MOF-TiO2 for the photocatalytic degradation of methylene blue

Abstract

Herein, we report a controllable strategy for fabricating monodispersed microspheres composed of poly(butyl methacrylate) (BMA) and silane-modified Cu/Ni-embedded metal–organic framework (MOF)-TiO₂ composites (denoted as BMA@Cu/Ni@MOF-TiO₂ microspheres) for efficient photocatalytic degradation. Monodispersed oil-in-water (O/W) emulsion templates containing silane-modified Cu/Ni@MOF-TiO₂ in the oil phase were prepared using a microfluidic device. Utilizing benzildimethyl ketal (BDK) as a photoinitiator, porous microspheres could be obtained through a straightforward photopolymerization process initiated by ultraviolet light. When the concentration of the surfactant polyglycerol polyricinoleate (PGPR 90) was 14% (w/v) and that of the crosslinker trimethylolpropane trimethacrylate (TMPTMA) was 12% (w/v), the BMA@Cu/Ni@MOF-TiO₂ microspheres demonstrated good monodispersity, with the average diameter of 180.7 μm and coefficient of variation (CV) of 3.64%. When the silane-modified Cu/Ni@MOF-TiO₂ loading was 0.4% (w/v), the removal rate for methylene blue (MB) reached 96.2% in 20 min, which is higher than that of powdered catalysts (86.6%). Under optimal conditions, the removal rate for methylene blue reached 99.3% within 50 min. Moreover, after five cycles of testing, degradation efficiency remained above 97.94%, which strongly demonstrates the reusability of the BMA@Cu/Ni@MOF-TiO₂ microspheres. The microspheres can efficiently photocatalytically degrade MB in harsh acid or alkaline environments (pH = 3–11) with good recyclability. The photocatalytic mechanism involved the generation of electron–hole pairs in Cu/Ni@MOF-TiO₂ under light irradiation, which reacted with O₂ to produce reactive oxygen species (ROS) to degrade MB. The characterization results of XPS and FTIR analyses show that silane-modified Cu/Ni@MOF-TiO₂ was successfully loaded into the microspheres. The BMA@Cu/Ni@MOF-TiO₂ microspheres exhibited a specific surface area of 5.962 m² g⁻¹ and a specific volume of 2.491 cm³ g⁻¹, providing sufficient diffusion channels and active sites for MB. Therefore, the BMA@Cu/Ni@MOF-TiO₂ microspheres demonstrated excellent recyclability, high stability and attractive photocatalytic degradation efficiency and show potential application prospects in the future treatment of dye wastewater.