4 research outputs found
Effective Strategy toward Obtaining Reliable Breakthrough Curves of Solid Adsorbents
Metal–organic frameworks (MOFs) have demonstrated
their
versatility in a wide range of applications, including chemical separation,
gas capture, and storage. In industrial adsorption processes, MOFs
are integral to the creation of selective gas adsorption fixed beds.
In this context, the assessment of their separation performance under
relevant conditions often relies on breakthrough experiments. One
aspect frequently overlooked in these experiments is the shaping of
MOF powders, which can significantly impact the accuracy of breakthrough
results. In this study, we present an approach for immobilizing MOF
particles on the surface of glass beads (GBs) utilizing trimethylolpropane
triglycidyl ether (TMPTGE) as a binder, leading to the creation of
MOF@GB materials. We successfully synthesized five targeted MOF composites,
namely, SIFSIX-3-Ni@GB, CALF-20@GB, UiO-66@GB, HKUST-1@GB, and MOF-808@GB,
each possessing distinct pore sizes and structural topologies. Characterization
studies employing powder X-ray diffraction and adsorption isotherm
analyses demonstrated that MOFs@GB retained their crystallinity and
73–90% of the Brunauer–Emmett–Teller area of
their parent MOFs. Dynamic breakthrough experiments revealed that,
in comparison to their parent MOFs, MOF@GB configurations enhanced
the accuracy of breakthrough measurements by mitigating pressure buildup
and minimizing reductions in the gas flow rate. This work underscores
the significance of meticulous experimental design, specifically in
shaping MOF powders, to optimize the efficacy of breakthrough experiments.
Our proposed strategy aims to provide a versatile platform for MOF
powder processing, thereby facilitating more reliable breakthrough
experiments
Rationally Tailored Mesoporous Hosts for Optimal Protein Encapsulation
Proteins play important roles in the therapeutic, medical
diagnostic,
and chemical catalysis industries. However, their potential is often
limited by their fragile and dynamic nature outside cellular environments.
The encapsulation of proteins in solid materials has been widely pursued
as a route to enhance their stability and ease of handling. Nevertheless,
the experimental investigation of protein interactions with rationally
designed synthetic hosts still represents an area in need of improvement.
In this work, we leveraged the tunability and crystallinity of metal–organic
frameworks (MOFs) and developed a series of crystallographically defined
protein hosts with varying chemical properties. Through systematic
studies, we identified the dominating mechanisms for protein encapsulation
and developed a host material with well-tailored properties to effectively
encapsulate the protein ubiquitin. Specifically, in our mesoporous
hosts, we found that ubiquitin encapsulation is thermodynamically
favored. A more hydrophilic encapsulation environment with favorable
electrostatic interactions induces enthalpically favored ubiquitin–MOF
interactions, and a higher pH condition reduces the intraparticle
diffusion barrier, both leading to a higher protein loading. Our findings
provide a fundamental understanding of host–guest interactions
between proteins and solid matrices and offer new insights to guide
the design of future protein host materials to achieve optimal protein
loading. The MOF modification technique used in this work also demonstrates
a facile method to develop materials easily customizable for encapsulating
proteins with different surface properties
Biomimetic Mineralization of Large Enzymes Utilizing a Stable Zirconium-Based Metal-Organic Frameworks
Enzymes
are natural catalysts for a wide range of metabolic chemical
transformations, including selective hydrolysis, oxidation, and phosphorylation.
Herein, we demonstrate a strategy for the encapsulation of enzymes
within a highly stable zirconium-based metal-organic framework. UiO-66-F4 was synthesized under mild conditions using an enzyme-compatible
amino acid modulator, serine, at a modest temperature in an aqueous
solution. Enzyme@UiO-66-F4 biocomposites were then formed
by an in situ encapsulation route in which UiO-66-F4 grows around the enzymes and, consequently, provides protection
for the enzymes. A range of enzymes, namely, lysozyme, horseradish
peroxidase, and amano lipase, were successfully encapsulated within
UiO-66-F4. We further demonstrate that the resulting biocomposites
are stable under conditions that could denature many enzymes. Horseradish
peroxidase encapsulated within UiO-66-F4 maintained its
biological activity even after being treated with the proteolytic
enzyme pepsin and heated at 60 °C. This strategy expands the
toolbox of potential metal-organic frameworks with different topologies
or functionalities that can be used as enzyme encapsulation hosts.
We also demonstrate that this versatile process of in situ encapsulation of enzymes under mild conditions (i.e., submerged
in water and at a modest temperature) can be generalized to encapsulate
enzymes of various sizes within UiO-66-F4 while protecting
them from harsh conditions (i.e., high temperatures, contact with
denaturants or organic solvents)
Programmed Polarizability Engineering in a Cyclen-Based Cubic Zr(IV) Metal–Organic Framework to Boost Xe/Kr Separation
Efficient
separation of xenon (Xe) and krypton (Kr) mixtures through
vacuum swing adsorption (VSA) is considered the most attractive route
to reduce energy consumption, but discriminating between these two
gases is difficult due to their similar properties. In this work,
we report a cubic zirconium-based MOF (Zr-MOF) platform, denoted as
NU-1107, capable of achieving selective separation of Xe/Kr by post-synthetically
engineering framework polarizability in a programmable manner. Specifically,
the tetratopic linkers in NU-1107 feature tetradentate cyclen cores
that are capable of chelating a variety of transition-metal ions,
affording a sequence of metal-docked cationic isostructural Zr-MOFs.
NU-1107-Ag(I), which features the strongest framework polarizability
among this series, achieves the best performance for a 20:80 v/v Xe/Kr
mixture at 298 K and 1.0 bar with an ideal adsorbed solution theory
(IAST) predicted selectivity of 13.4, placing it among the highest
performing MOF materials reported to date. Notably, the Xe/Kr separation
performance for NU-1107-Ag(I) is significantly better than that of
the isoreticular, porphyrin-based MOF-525-Ag(II), highlighting how
the cyclen core can generate relatively stronger framework polarizability
through the formation of low-valent Ag(I) species and polarizable
counteranions. Density functional theory (DFT) calculations corroborate
these experimental results and suggest strong interactions between
Xe and exposed Ag(I) sites in NU-1107-Ag(I). Finally, we validated
this framework polarizability regulation approach by demonstrating
the effectiveness of NU-1107-Ag(I) toward C3H6/C3H8 separation, indicating that this generalizable
strategy can facilitate the bespoke synthesis of polarized porous
materials for targeted separations