Search for: All records

Metal-organic frameworks (MOFs) have attracted much attention in the past decades owing to their amazing properties, including rich surface chemistry, flexible structure, superior surface area, and tunable porosity. MOFs are conventionally synthesized via wet-chemistry methods, which, however, are oftentimes plagued by long reaction durations, inhomogeneous mixing, and limited batch processes. This article reviews a rapid microdroplet-based nanomanufacturing process to fabricate MOFs-based functional materials with controlled hierarchical nanostructures to overcome the aforementioned disadvantages of wet-chemistry processes. The general formation pathways of MOFs inside the microdroplets were investigated by both experimental and theoretical approaches. Further, strategies to integrate MOFs with semiconductors to form hybrid photocatalysts are also summarized towards addressing environmental challenges, with a major focus on CO₂photoreduction. The quantitative mechanisms of CO₂adsorption, activation, and charge transfer within the hybrid nanostructures were explored by variousin-situtechniques, such as diffuse reflectance infrared Fourier transform spectroscopy, photoluminescence spectroscopy, and x-ray photoelectron spectroscopy. This review provides a new avenue for the rational design of MOFs-based functional materials to tackle a variety of environmental issues, including but not limited to global warming, air pollution, and water contamination.

 

With the increased bacteria-induced hospital-acquired infections (HAIs) caused by bio-contaminated surfaces, the requirement for a safer and more efficient antibacterial strategy in designing personal protective equipment (PPE) such as N95 respirators is rising with urgency. Herein, a self-decontaminating nanofibrous filter with a high particulate matter (PM) filtration efficiency was designed and fabricated via a facile electrospinning method. The fillers implemented in the electrospun nanofibers were constructed by grafting a layer of antibacterial polymeric quaternary ammonium compound (QAC), that is, poly[2-(dimethyl decyl ammonium) ethyl methacrylate] (PQDMAEMA), onto the surface of metal–organic framework (MOF, UiO-66-NH 2 as a model) to form the active composite UiO-PQDMAEMA. The UiO-PQDMAEMA filter demonstrates an excellent PM filtration efficiency (>95%) at the most penetrating particle size (MPPS) of 80 nm, which is comparable to that of the commercial N95 respirators. Besides, the UiO-PQDMAEMA filter is capable of efficiently killing both Gram-positive ( S. epidermidis ) and Gram-negative ( E. coli ) airborne bacteria. The strong electrostatic interactions between the anionic cell wall of the bacteria and positively charged nitrogen of UiO-PQDMAEMA are the main reasons for severe cell membrane disruption, which leads to the death of bacteria. The present work provides a new avenue for combating air contamination by using the QAC-modified MOF-based active filters. 

Nitro-functionalized metal–organic frameworks (MOFs), such as Al-MIL-53-NO 2 , have been widely used in quantitative hydrogen sulfide (H 2 S) detection based on the “turn-on” effect, where fluorescence enhancements were observed upon contact with H 2 S. This was believed to be caused by the fact that the electron-withdrawing –NO 2 groups in the initial non-luminescent MOFs were reduced to electron-donating –NH 2 groups in the sensing process. However, since most H 2 S detection is conducted in a suspension system consisting of MOFs and solvents, it is still unclear whether these –NH 2 groups are on MOFs or in the liquid. Using Al-MIL-53-NO 2 as a model MOF, this work aims to answer this question. Specifically, the supernatant and undissolved particles separated from the Al-MIL-53-NO 2 suspensions after being exposed to H 2 S were analyzed systematically. The results showed that it is the free BDC-NH 2 (2-aminobenzene-1,4-dicarboxylic acid) in the solution rather than the formation of Al-MIL-53-NH 2 that really caused the fluorescence enhancement. In particular, the formed BDC-NH 2 was reduced from the shedded BDC-NO 2 (2-nitrobenzene-1,4-dicarboxylic acid) during the decomposition of Al-MIL-53-NO 2 , which was attacked by OH − in the NaHS solution. We anticipate that this work will offer new ways of tracing fluorophores for MOF-based sensing applications in aqueous systems.