Metal–organic frameworks (MOFs)
have gained considerable
attention as drug delivery platforms over the past decade owing to
their tunable physiochemical properties, biodiversity, and capability
to encapsulate sizable active compound loadings. Nevertheless, many
fundamental properties pertaining to MOFs’ pharmacokinetic
performances as drug carriers have been poorly investigated. One such
property is the relationship between the MOF metal center solubility
and drug release rate. In this study, we investigated this relationship
within the M-MOF-74 family by impregnating 30 or 50 wt % curcumin
on either Mg-, Ni-, Zn-, or Co-MOF-74. The drug delivery performance
of the materials was assessed in phosphate buffered saline solution
by high-performance liquid chromatography over a time period of 0–24
h. From these experiments, it was determined that the 30 wt % curcumin
loading led to increased drug delivery and kinetics compared to the
50 wt % loading regardless of the metal center, as the lower drug
concentration did not hinder diffusion from the MOF pores. As such,
the optimal curcumin loading within the M-MOF-74 family was concluded
to be greater than 30 wt % but less than 50 wt %. These experiments
also revealed that using Mg-MOF-74 as a drug carrier produced a twofold
enhancement in the release rate from 0.15 to 0.30 h1/2 compared
to the other three metal centers, where Mg-MOF-74’s improved
pharmacokinetics were attributed to the increased group II Mg solubility
compared to Ni, Co, or Zn transition metals. On the basis of these
findings, it was concluded that to promote rapid pharmacokinetics,
it is essential to use MOFs with more soluble metal centers to promote
dissolution of the nanocarrier. While this study focused on M-MOF-74,
we expect that this conclusion has implications to other crystallites
as well.
3D printing has emerged as an attractive way of formulating structured adsorbents, as it imparts lower manufacturing costs compared to hydraulic extrusion while also allowing for unprecedented geometric control. However, binderless structures have not been fabricated by 3D printing, as ink formulation has previously required clay binders which cannot be easily removed. In this study, we report the development of a facile approach to shape engineer binderless zeolites. 3D-printed inks comprised of 13X, 5A, ZSM-5, and experimental South African zeolites were prepared using gelatin and pectin as binding agents along with dropwise addition of various solvents. After printing, the dried monoliths were calcined to remove the biopolymers and form 100% pure zeolite structures. From N 2 physisorption and CO 2 adsorption measurements at 0 • C, all monoliths showed narrowing below 1 nm from their powders, which was attributed to pore malformation caused by intraparticle bridging during calcination. The various adsorption isotherms indicated that this narrowing led to varying degrees of enhanced adsorption capacities for all three gases, as the slightly smaller pores increased electrostatic binding between the sorbent walls and captured species. Analysis of CO 2 adsorption performance revealed comparable diffusivities and adsorption capacities to the commercial bead analogues, implying that biopolymer/ zeolite printing can produce contactors which are competitive to commercial benchmarks. The binderless monoliths also exhibited faster diffusivities compared to zeolite monoliths produced by conventional direct ink writingon account of an enhancement in macroporosityhighlighting that this new method enhances the kinetic properties of 3D-printed scaffolds. As such, the sacrificial biopolymer technique is an effective and versatile approach for 3D printing binderless zeolite structures.
Oxidative propane dehydrogenation using CO2 (CO2‐ODHP) is a potential alternative for propylene synthesis. In this study, bifunctional catalysts (V2O5, ZrO2, Cr2O3, and Ga2O3 doped H‐ZSM‐5) are synthesized through additive manufacturing for CO2‐ODHP. Characterization and correlation between the various characterizations and the catalytic results indicates that the direct 3D printing of metal oxides alongside H‐ZSM‐5 can considerably modify the surface properties and bulk oxide phase dispersion, thus leading to enhanced metal oxide reducibility and exceptional CO2‐ODHP performance. Among the metal monoliths, the mixed oxide sample with 5 wt% Cr, 10 wt% V, 10 wt% Zr, 10 wt% Ga and 65 wt% H‐ZSM‐5 displays the best activity, achieving ≈40% propane conversion, 95% propylene selectivity, and zero benzene/toluene/xylene production. Upon eliminating CO2, the catalyst monoliths all retain their long‐term stability; however, the propane conversions decrease by ≈3% and the propylene selectivities decreased by 5–15%. Nevertheless, all five samples examined here demonstrate exceptional catalytic activities and prolonged stabilities, which are attributed to the even distribution of surface acid sites produced by direct printing of the oxide and zeolite components. Overall, this study presents a novel way of manufacturing bifunctional structured catalysts that exhibit exceptional ODHP performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.