Constructing Mesoporous Adsorption Channels and MOF–Polymer Interfaces in Electrospun Composite Fibers for Effective Removal of Emerging Organic Contaminants

Abstract

Recently, metal–organic framework (MOF)-based electrospun fibers have attracted considerable attention as adsorbents for organic contaminant removal from water. To prepare these fibers, two common strategies including blending electrospinning and surface coating are employed. However, fibers obtained from the two strategies still have some disadvantages, such as adsorption site blockage and unstable loading. Here, we constructed interconnected mesopores in the electrospun zeolitic imidazolate framework-8 (ZIF-8)/polyacrylonitrile (PAN) fibers with the assistance of poly­(vinylpyrrolidone) to expose more adsorption sites of ZIF-8 and make ZIF-8 more stable. Moreover, the mesopores could also enhance the diffusion of contaminant molecules and create MOF–polymer interfaces in the fiber, which improve the adsorption rate and adsorption capacity, respectively. The obtained fibers were used to adsorb antibiotic tetracycline from water. Benefiting from the mesoporous adsorption channels and the MOF–polymer interface, porous ZIF-8/PAN fibers showed faster adsorption kinetics than ZIF-8/PAN blending fibers and larger adsorption capacity than ZIF-8-coated PAN fibers and ZIF-8/PAN blending fibers. The maximum adsorption capacity of porous ZIF-8/PAN fibers was 885.24 mg/g, which is close to that of pure ZIF-8. After 10 adsorption–desorption cycles, the removal efficiency was still above 97%. In addition, porous ZIF-8/PAN fibers could act as the membrane adsorbents to dynamically separate tetracycline with a treated capacity of 9.93 × 103 bed volumes. These results demonstrate that our prepared porous ZIF-8/PAN fibers have great potential in antibiotic drug removal.

Facile One-Step Metal–Organic Framework Surface Polymerization Method

“…Meanwhile, the strong intermolecular connectivity through coordination bonds has granted MOFs with permanent porosity, a signature attribute of porous materials. − Nevertheless, both crystallinity and permanent porosity come at a cost of losing the materials’ flexibility and processability, which are two essential qualities when it comes to many industrial applications. Therefore, MOF particles are often blended with soft polymers in the form of dense membranes, − foams, − fibers, − and even fluids , to endow MOFs with improved processability. However, dispersing a rigid powdery substance into a soft polymeric medium often confronts a challenge of poor interfacial compatibility because of mechanical and chemical mismatch, which may lead to consequences such as interfacial defects, poor dispersibility, weakened mechanical strength, etc. − …”

Multifunctional Membranes—A Versatile Approach for Emerging Pollutants Removal

“…Adsorption [230] Fiber membrane with interconnected mesopores based on an electrospun zeolitic imidazolate framework-8 (ZIF-8)/PAN fibers integrated into PVP. Method: zinc salt and 2-methylimidazole as precursors into PVP to obtain electrospun fiber membrane, PVP removal at 50 Adsorption [236] Graphene oxide (GO)/poly(vinylidene fluoride) (PVDF) electrospun nanofibrous membranes (ENMs).…”

Removal of Acidic Organic Ionic Dyes from Water by Electrospinning a Polyacrylonitrile Composite MIL101(Fe)-NH2 Nanofiber Membrane

“…In addition, the mesopores enhanced the diffusion of pollutant molecules and created an MOF polymer interface in the fiber, which improved the adsorption rate and adsorption capacity, respectively. The fibers were used to adsorb tetracycline, an antibiotic, from water [ 36 ]. Maya et al demonstrated a general scheme for fabricating freestanding polymer fibers embedded in porous fibers, wherein the fibers themselves served as microreactors for the in situ growth of porous fiber crystals.…”