Olefin/paraffin separation is an important but challenging and energy-intensive process in petrochemical industry. The realization of carbons with size-exclusion capability is highly desirable but ...rarely reported. Herein, we report polydopamine-derived carbons (PDA-Cx, where x refers to the pyrolysis temperature) with tailorable sub-5 Å micropore orifices together with larger microvoids by one-step pyrolysis. The sub-5 Å micropore orifices centered at 4.1-4.3 Å in PDA-C800 and 3.7-4.0 Å in PDA-C900 allow the entry of olefins while entirely excluding their paraffin counterparts, performing a precise cut-off to discriminate olefin/paraffin with sub-angstrom discrepancy. The larger voids enable high C
H
and C
H
capacities of 2.25 and 1.98 mmol g
under ambient conditions, respectively. Breakthrough experiments confirm that a one-step adsorption-desorption process can obtain high-purity olefins. Inelastic neutron scattering further reveals the host-guest interaction of adsorbed C
H
and C
H
molecules in PDA-Cx. This study opens an avenue to exploit the sub-5 Å micropores in carbon and their desirable size-exclusion effect.
Sub-nanometer materials(SNMs) define the emergent functional material system with their characteristic dimensions at sub-1 nm scale and they can be generally constructed with the sub-1 nm molecular ...clusters as the basic structural units. Due to their extremely small sizes, the sub-nm scale particles possess diffusive dynamics in their bulk with an energy level close to typical thermal fluctuation. Meanwhile, the volume fraction of surface structures becomes dominant and the dynamics of surface structures can be distinguishable from their diffusive dynamics. The research on the dynamics of SNM is key to the understanding of their unique properties in comparison to small molecule and nano-material systems. This review paper summarizes recent progresses in the studies of relaxation dynamics of SNM upon the combinatory application of X-ray/neutron scattering, dielectric spectroscopy and rheometric technology. The functional materials inspired by the dynamics investigations with applications in mechanical strengthening, ion conduction, and gas separation are also reviewed. In the end, challenges and outlooks on the theories, characterizations and the prediction of possible new functionalities of SNMs are discussed.
The nanoconfinement of proton carrier molecules may contribute to the lowing of their proton dissociation energy. However, the free proton transportation does not occur as easily as in liquid due to ...the restricted molecular motion from surface attraction. To resolve the puzzle, herein, imidazole is confined in the channels of porous coordination polymers with tunable geometries, and their electric/structural relaxations are quantified. Imidazole confined in a square‐shape channels exhibits dynamics heterogeneity of core‐shell‐cylinder model. The core and shell layer possess faster and slower structural dynamics, respectively, when compared to the bulk imidazole. The dimensions and geometry of the nanochannels play an important role in both the shielding of the blocking effect from attractive surfaces and the frustration filling of the internal proton carrier molecules, ultimately contributing to the fast dynamics and enhanced proton conductivity.
Imidazole confined in porous coordination polymers’ channels exhibits dynamics heterogeneity of typical core‐shell‐cylinder model, in which the core‐layer possess faster rotating dynamics contributing to enhanced proton conductivity.
The emergence of polymers with intrinsic microporosity provides solutions for flexible gas separation membranes with both high gas permeability and selectivity. However, their applications are ...significantly hindered by the costly synthetic efforts, limited availability of chemical systems, and narrow window of microporosity sizes. Herein, flexible mixed matrix membranes with tunable intrinsic microporosity can be facilely fabricated from the coordination assembly of polymer brushes and coordination nanocages. Polymer brushes bearing isophthalic acid side groups can coordinate with Cu2+ to assemble into polymer networks crosslinked by 2 nm nanocages. The semi‐flexible feature of the polymer brush and the high crosslinking density of the network prevent the network from collapsing during solvent removal and the obtained aerogels demonstrate hierarchical structure with dual porosity from the crosslinked polymer network and coordination nanocage, respectively. The porosity can be facilely tuned via the amount of Cu2+ by regulating the network crosslinking density and nanocage loadings, and finally, optimized gas separation that surpasses Robeson upper bound for H2/CO2 can be achieved. The coordination‐driven assembly protocol paves a new avenue for the cost‐effective synthesis of polymers with intrinsic microporosity and the fabrication of flexible gas separation membranes.
Coordination nanocages are integrated with polymer brush for mixed matrix membranes with hierarchical porosity while the high free volume of polymer network from frustrated packing enables the access of nanocage to gas molecules, contributing to fast gas transport pathways and excellent gas selectivity to surpass upper bound for H2/CO2.
Back Cover: A new strategy for the design of polymers of intrinsic microporosity (PIMs) is developed from the coordination‐driven assembly of polymer brush and metal ions and their pore size ...distribution can be conveniently tuned via the amount of introduced metal ions as demonstrated by Panchao Yin and co‐workers in article number 2300477.
The emergence of polymers with intrinsic microporosity provides solutions for flexible gas separation membranes with both high gas permeability and selectivity. However, their applications are ...significantly hindered by the costly synthetic efforts, limited availability of chemical systems, and narrow window of microporosity sizes. Herein, flexible mixed matrix membranes with tunable intrinsic microporosity can be facilely fabricated from the coordination assembly of polymer brushes and coordination nanocages. Polymer brushes bearing isophthalic acid side groups can coordinate with Cu
to assemble into polymer networks crosslinked by 2 nm nanocages. The semi-flexible feature of the polymer brush and the high crosslinking density of the network prevent the network from collapsing during solvent removal and the obtained aerogels demonstrate hierarchical structure with dual porosity from the crosslinked polymer network and coordination nanocage, respectively. The porosity can be facilely tuned via the amount of Cu
by regulating the network crosslinking density and nanocage loadings, and finally, optimized gas separation that surpasses Robeson upper bound for H
/CO
can be achieved. The coordination-driven assembly protocol paves a new avenue for the cost-effective synthesis of polymers with intrinsic microporosity and the fabrication of flexible gas separation membranes.
Water confined on metal oxide surface plays significant roles in heterogeneous catalysis. Heteropolyacid, a 1.2 nm‐metal oxide cluster with well‐defined structure, is applied as a model to understand ...the dynamics of water on its surface. The surface water strongly associates with heteropolyacid cluster and form the so‐called ‘pseudoliquid phase’ where catalytic reactions are conducted. Broadband dielectric spectroscopy and differential scanning calorimetry have been applied to probe the dynamics of water in this pseudoliquid phase. A supercooling phase transition of water below its normal melting temperature and a dipolar glassy relaxation behaviour due to the hindered dynamics of water have been observed. The rich dynamic behavior on the surface of such well‐defined metal clusters provide new perspectives to understand the properties of surface water and their relation to catalytic performance of heteropolyacid.
Heteropolyacid: The long‐time dynamics of confined water on the dodecatungstosilicic acid surface have been investigated. A phase transition in its supercooled region and a dipolar glassy relaxation mode are observed, which enable understanding the dynamics of catalytic substances in the pseudoliquid phase.
Abstract
Graphite anodes experience co‐intercalation of K
+
ions and solvent in ether‐based electrolytes, which enables ultrafast kinetics of potassium‐ion storage. The potassium‐ion storage ...mechanisms of amorphous soft carbon (SC) and hard carbon (HC) anodes in ether‐based electrolytes are ambiguous. Herein, the co‐intercalation mechanisms of SC and HC in ether‐based electrolytes are elucidated. The solvated K
+
intercalates with a solvation structure, which avoids the sluggish desolvation process. Thus, HC and SC anodes display excellent rate capabilities. Moreover, the SC anode forms ternary K‐graphite intercalation compounds during the potassiation process. It is also demonstrated that solvated K
+
is not only stored in the spacing between graphene nanodomains but can also be stored in the closed pores of HC, enabling higher capacities than pure K
+
intercalation in ester‐based electrolytes. Nevertheless, the co‐intercalation causes the large volume expansion of SC and HC, giving rise to irreversible structural damage and capacity decay of SC and HC. The strong interaction between K
+
ions and ether molecules is the main reason for the co‐intercalation. A thick and organic‐rich solid electrolyte interphase film formed in ester‐based electrolytes can hinder the co‐intercalation in ether‐based electrolytes.
The strong inter-phase attraction is required for the effective and stable integration of inorganics and polymers in mixed matrix membranes (MMMs), which would impact the structures and microscopic ...dynamics of the two phases and cause unexpected deviation of MMM performance from original design; however, the understanding of its structure-property relationship is still poor. Herein, 2 nm coordination nanocage (CNC) with well-defined, monodispersed structure is complexed with poly(4-vinyl pyridine-r-n-butyl acrylate) (P4VP-co-PnBA) via both coordination and hydrogen bonding to afford model systems. The surface interaction between the two phases is quantified by the thickness of absorbed layers of polymers on CNC surface as well as the segmental dynamics of polymers. In broadband dielectric spectroscopy (BDS) studies, accelerated chain dynamics can be observed in the nanocomposites with loadings of CNC, which is originated from the frustrated packing of polymers absorbed on CNC surface. The co-effect of interfacial layer thickness and chain dynamics leads to the non-monotonic dependence of the MMMs’ gas permeabilities on CNC concentrations. The temperature dependence of their gas permeability and chain dynamics are both explored and the two processes are fully decoupled at temperatures higher than 333 K due to the weakening of multiple supramolecular interaction. Our discoveries provide microscopic and quantitative understanding on structure-property relationship of MMMs, which benefits directly to the rational design of polymer structures for optimized gas separation performance.
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•Quantified structure-property relationship of mixed matrix membranes is provided.•The dynamics of polymer are probed for understanding the inter-phase interaction.•The information of interfacial polymer layers on nano-filler surface are revealed.•The nonmonotonic dependence of gas permeabilities on filler loadings is deciphered.
