Construction of Janus-structured ZnO@ZIF-8(-NH2)/cellulose nanofiber foam for highly efficient adsorption and photocatalysis-assisted desorption of tetracycline

MOF-based foam has potential applications in removing antibiotics from water. However, shaping MOFs into foam usually sacrifices a portion of the specific surface area and thus reduces their adsorption properties, i.e., adsorption uptake and regeneration efficiency. Herein, a Janus-structured ZnO@ZIF-8(-NH2)/cellulose nanofiber foam (C-ZnO0.5/ZAA foam) was designed as a photo-regenerable adsorbent for highly efficient tetracycline (TC) removal. Janus structured C-ZnO0.5/ZAA foam with a hybrid ZnO/ZIF-8 interface was constructed by an interface-induced epitaxial growth strategy via using ZnO as anchor points for amino-imidazolamide (AICA) modified ZIF-8 growth. The obtained C-ZnO0.5/ZAA foam showed a relatively higher specific surface area (555.7 m(2) g(-1)) and hierarchical porous structure due to the high loading and dispersion of ZIF-8 on macroporous cellulose nanofiber foam compared to reported MOF foams. Adsorption and desorption performance showed that: (1) its adsorption capacity of TC reached up to 257 mg g(-1) at a low concentration of 20 mg L-1 at 25 degrees C, about 1.9-11.1 times higher adsorption uptake than that of state-of-the-art adsorbents; (2) with photocatalysis-assisted regeneration, this foam achieved complete desorption in water within only 4 h after reaching TC adsorption saturation, whose desorption efficiency had increased 7-8 times that of the traditional regeneration method; (3) through a semi-continuous fixed-bed set-up, C-ZnO0.5/ZAA foam exhibited excellent reusability for TC removal, with only a 5% decrease in initial uptake after 10 cyclic runs. This work proposes a strategy for designing and fabricating a photo-regenerable MOF-based foam with high adsorption capacity for highly efficient capture of TC from wastewater.