Assembly of MOFs/polymer hydrogel derived Fe3O4-CuO@hollow carbon spheres for photochemical oxidation: Freezing replacement for structural adjustment

We report a new strategy for fabrication of magnetic core–shell Fe3O4[email protected] hollow sphere derived from MOFs/sodium alginate (SA) hydrogel through one-pot synthesis of ferrocene CVD and pyrolysis. Development of freezing-replacement by n-hexane overcame SA capsule shrink induced by heat-treatment and created highly-stable coconut shell-like superstructures, which allowed active sites homogeneously distributed on no-defect surface and improved magnetic and photocatalytic activity of composites. The turn over frequency (TOF) of Fe3O4[email protected] for organic pollutants degradation was 2.3 h−1 under visible light irradiation, much higher than most of reported catalysts. The synergistic effect of bimetallic clusters and carbon matrix facilitated the charge separation and accelerated H2O2 activation to yield high active radicals. Layer structure and good interfacial contact of metallic sites and porous carbon was beneficial for enhancing photocatalytic activity. The progresses offer a feasible route to rational design of MOF-derived hybrid hollow materials with tailored structure and properties for various applications.