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He et al. Soft Sci 2024;4:37 https://dx.doi.org/10.20517/ss.2024.32 Page 15 of 27

luminescence collection while protecting the MOFs from harsh environments. At the same time, it allowed
for analyte penetration and interaction. The platform showed highly selective detection of explosive picric
acid using water- and thermally stable europium(Eu), 1,4-naphthalenedicarboxylic acid (H2NDC)
(EuNDC) as the fluorescent material, as demonstrated in a representative experiment [Figure 7B].

Organophosphorus pesticides, widely used for their high efficiency, are highly toxic and harmful to humans.
Overuse disrupts ecosystems and threatens human health. To address this, Jia et al. developed MOF-on-
MOF hydrogels capable of detecting pesticides and degrading them after use . They fabricated a composite
[93]
material (ZIF-8-on-Zn @SA) by using MOF(Zn ) as the core and wrapping it with ZIF-8. The porous
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structure of ZIF-8 exposes nitrogen sites, enabling high chemical activity and strong fluorescent emission.
This composite can detect thiophanate-methyl (TM) visually, offering a broad linear range, low detection
limit, and high recovery rates, making it promising for agricultural applications. Enzyme-based biosensing
can be selective and efficient, but enzymes often lose activity. To overcome this, Zhong et al. created a
hybrid sensor by co-encapsulating enzymes in ZIF-8 and double-crosslinked alginate [Figure 7C] . These
[94]
enzymes convert glucose into a blue-violet product, facilitating colorimetric glucose biosensing with
smartphone integration. The enzymes remained stable and active for 30 days at room temperature. Further
advances were made by Shen et al., who grafted UiO-66-NH and PAMAM onto sodium alginate to create
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[95]
hydrogels (SA@UiO-66-NH @PAMAM) that independently degrade organophosphorus derivatives .
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Building on this, Chen et al. developed a MOF-based hydrogel that visualizes nerve agent hydrolysis via a
yellow color change . This hydrogel can be easily shaped into cotton and used as a multifunctional sensor
[94]
with smartphone integration. Sun et al. designed a colorimetric sensor by combining porphyrin-based
MOFs with polyacrylamide-DNA hydrogel, achieving strong peroxidase-like activity and stability . The
[96]
sensor demonstrated excellent selectivity, a wide linear range, and low detection limits, making it both user-
friendly and effective for chemical sensing. In another approach, Lu et al. developed a chemiluminescence
sensor for detecting organophosphorus pesticides and D-amino acids . Using N-(4-aminobutyl)-N-
[13]
ethylisoluminol/Co /CS hydrogels as the matrix, catalyzed by MOFs [Figure 7D], they enhanced sensor
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sensitivity. The system detects up to 17 types of organophosphates by inhibiting acetylcholinesterase
(AChE) activity, which reduces H O production and affects the chemiluminescence system. It can also
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detect other reactants that produce H O .
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The collective endeavors of various research teams showcase the remarkable progress in developing MOFs-
based hydrogels for advanced and selective chemical sensing applications. Furthermore, the innovative
applications extend to addressing environmental concerns, such as the detection of organophosphorus
pesticides and the development of multifunctional hydrogels for agriculture. These advancements highlight
the potential of MOFs-based hydrogels as crucial contributors to the future of detection and sensor
technologies, providing solutions to pressing challenges across various fields, including healthcare and
environmental protection.

Biomedical application
Antibacterial
MOFs-based hydrogels have emerged as a cutting-edge approach to address the challenges associated with
bacterial infections and delayed healing. Bacterial adhesion and colonization hinder wound healing.
According to the three reported MOFs, Gwon et al. fabricated three bioactive MOFs-based hydrogels with
diacrylated polyethylene glycol, 4-arm thiolated polyethylene glycol (PEG), and MOFs . The release test of
[97]
MOFs-based hydrogels showed high-performance antibacterial activities and stability. Moreover, one of
them exhibited an excellent 99.9% antibacterial effect without cytotoxicity in human dermal fibroblasts.