Electrochemical deposition has emerged as a novel approach to fabricate metal–organic framework (MOF) films. Here, for the first time, an aqueously cathodic deposition (ACD) approach is developed to fabricate ZIF‐8 type of MOF membranes without addition of any supporting electrolyte or modulator. The fabrication process uses 100% water as the sole solvent and a low‐defect density membrane is obtained in only 60 min under room temperature without any pre‐synthesis treatment. The membrane exhibits superior performance in C3H6/C3H8 separation with 182 GPU C3H6 permeance and 142 selectivity, making it sit at the upper bound of permeance versus selectivity graph, outperforming majority of the published data up to 2019. Notably, this approach uses an extremely low current density (0.13 mA cm−2) operated under an ultrafacile apparatus set‐up, enabling an attractive way for environmentally friendly, energy efficient, and easily scalable MOF membrane fabrications. This work demonstrates a great potential of aqueously electrochemical deposition of MOF membrane in the future research.
Generating pores in graphene by decoupled nucleation and expansion is desired to achieve a fine control over the porosity, and is desired to advance several applications. Herein, epoxidation is introduced, which is the formation of nanosized epoxy clusters on the graphitic lattice as nucleation sites without forming pores. In situ gasification of clusters inside a transmission electron microscope shows that pores are generated precisely at the site of the clusters by surpassing an energy barrier of 1.3 eV. Binding energy predictions using ab initio calculations combined with the cluster nucleation theory reveal the structure of the epoxy clusters and indicate that the critical cluster is an epoxy dimer. Finally, it is shown that the cluster gasification can be manipulated to form Å‐scale pores which then effectively sieve gas molecules based on their size. This decoupled cluster nucleation and pore formation will likely pave the way for an independent control of pore size and density.
Our method hinders the Ostwald ripening of polycrystalline MOF film during the solvothermal synthesis, allowing the growth of high-quality MOF films in just 8 min at room temperature.
Predictable and tunable
etching of angstrom-scale nanopores in
single-layer graphene (SLG) can allow one to realize high-performance
gas separation even from similar-sized molecules. We advance toward
this goal by developing two etching regimes for SLG where the incorporation
of angstrom-scale vacancy defects can be controlled. We screen several
exposure profiles for the etchant, controlled by a multipulse millisecond
treatment, using a mathematical model predicting the nucleation and
pore expansion rates. The screened profiles yield a narrow pore-size-distribution
(PSD) with a majority of defects smaller than missing 16 carbon atoms,
suitable for CO
2
/N
2
separation, attributing
to the reduced pore expansion rate at a high pore density. Resulting
nanoporous SLG (N-SLG) membranes yield attractive CO
2
permeance
of 4400 ± 2070 GPU and CO
2
/N
2
selectivity
of 33.4 ± 7.9. In the second etching regime, by limiting the
supply of the etchant, the nanopores are allowed to expand while suppressing
the nucleation events. Extremely attractive carbon capture performance
marked with CO
2
permeance of 8730 GPU, and CO
2
/N
2
selectivity of 33.4 is obtained when CO
2
-selective polymeric chains are functionalized on the expanded nanopores.
We show that the etching strategy is uniform and scalable by successfully
fabricating high-performance centimeter-scale membrane.
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