Page 131 - Read Online

Lee et al. Microstructures 2023;3:2023021 https://dx.doi.org/10.20517/microstructures.2023.08 Page 13 of 19

amorphous structures via temperature-induced amorphisation through melting upon heating followed by a
fast cooling (quenching) process at ambient pressure [92,93] . These ZIF glasses form a continuous random
network similar to the amorphous structure of silica glass. Also, these emerging new types of glasses show
[94]
structural diversity and unique properties compared to inorganic, organic and metallic glasses . Recently,
our group further developed this idea and successfully fabricated embedded perovskites within the ZIF glass
matrix. This nanocomposite not only showed significantly improved photoluminescence under UV light in
ambient conditions, but the stability also improved noticeably in most solvents. Figure 9 shows how CsPbI
3
perovskite is encapsulated within the ZIF-62 glass matrix after the sintering process and the phase
distribution based on ADF and SED-STEM spectroscopy .
[95]

SUMMARY AND OUTLOOK
In conclusion, the embedment of various quantum dots into microporous materials has shown enormous
potential for applications due to its ability to enhance long-term stability, reduce aggregation, improve
efficiency, increase active material density, provide protective layers, and achieve uniform distribution.
However, some of the methods are complicated and challenging to control during the fabrication process,
which makes upscaling difficult. Although most of the studies are still in their early stages, especially QDs in
COFs and MOFs, they have proved significant functionalities and potential. Based on above mentioned
strategies, we hope this Perspective has highlighted the promising future research directions related to QDs
in microporous structure.

(1) Biocompatible nanocomposite of QDs within microporous frameworks: The demand for biocompatible
quantum dots and microporous templates is rapidly increasing for a wide range of applications, including
disease detection, drug delivery, molecule detection, and cancer treatment. Currently, most of the research
on biocompatible QDs is focused on surface engineering, including surface organic ligand exchange,
polymer encapsulation and conjugation of biomolecules on the surface of QDs. However, those approaches
still experience several issues such as size uniformity, aggregation, and stability in the biological
environment. Furthermore, although there are numerous ongoing explorations for biocompatible and
biodegradable MOFs and COFs for biomedicine applications, there have been limited investigations to
combine biocompatible framework matrixes and QDs. Thus, by intermarriage of two biocompatible
materials, QDs and specifically tailored flameworks matrix, can improve the selectivity of QDs and enable
biological targeting of small molecules and antigens, as well as providing uniformity and stability to the
composite.

(2) MOF glasses: one of the most recent and significant progress in porous materials is the development of
MOF glasses. MOF glasses are new types of glasses that have unique characteristics compared with
traditional glass materials. As these emerging materials have only been studied for less than 10 years, there
are still many research gaps to investigate. We demonstrated a MOF glass with perovskite QD
nanocomposites that greatly improved interfacial connectivity, which MOF crystals have not been able to
achieve . Furthermore, MOF glasses can be obtained through mechanical vitrification or direct synthesis
[95]
[96]
as glass . Thus, researching various types of MOFs and QDs hybrid materials as well as alternative
fabrication routes of MOFs glass could open more new possibilities for QDs and MOF glasses
nanocomposite.

(3) Fundamental study of QDs within microporous structure: Although great efforts have been made to
fabricate QDs in microporous structures and improve their efficacy, there are remaining questions for a
deeper understanding of the nanocomposite due to its set of rich physiochemical properties and dynamic
interaction between two materials. In particular, x-ray-based techniques such as small-angle X-ray