The poor mechanical strength of graphene oxide (GO) membranes, caused by the weak interlamellar interactions, poses a critical challenge for any practical application. In addition, intrinsic but large-sized 2D channels of stacked GO membranes lead to low selectivity for small molecules. To address the mechanical strength and 2D channel size control, thiourea covalent-linked graphene oxide framework (TU-GOF) membranes on porous ceramics are developed through a facile hydrothermal self-assembly synthesis. With this strategy, thiourea-bridged GO laminates periodically through the dehydration condensation reactions via NH and/or SH with OCOH as well as the nucleophilic addition reactions of NH to COC, leading to narrowed and structurally well-defined 2D channels due to the small dimension of the covalent TU-link and the deoxygenated processes. The resultant TU-GOF/ceramic composite membranes feature excellent sieving capabilities for small species, leading to high hydrogen permselectivities and nearly complete rejections for methanol and small ions in gas, solvent, and saline water separations. Moreover, the covalent bonding formed at the GO/support and GO/GO interfaces endows the composite membrane with significantly enhanced stability.

To separate small molecules/species, it’s crucial but still challenging to narrow the 2D-interspacing of graphene oxide (GO) membranes without damaging the membrane. Here the fast deposition of ultrathin, defect-free and robust GO layers is realized on porous stainless steel hollow fibers (PSSHFs) by a facile and practical electrophoresis deposition (ED) method. In this approach, oxygen-containing groups of GO are selectively reduced, leading to a controlled decrease of the 2D channels of stacked GO layers. The resultant ED-GO@PSSHF composite membranes featured a sharp cutoff between C2 (ethane and ethene) and C3 (propane and propene) hydrocarbons and exhibited nearly complete rejections for the smallest alcohol and ion in aqueous solutions. This demonstrates the versatility of GO based membranes for the precise separation of various types of mixtures. At the same time, a robust mechanical strength of the ED-GO@PSSHF membrane is also achieved due to the enhanced interaction at GO/support and GO/GO interfaces.

Vanadia−titania−sulfate nanocatalysts for methanol oxidation to methyl formate (MF) were prepared by coprecipitation. When calcinated at 400 °C, both methanol conversion and MF selectivity reached ∼98.5% at reaction temperatures of 140−145 °C. Characterizations with several experimental techniques revealed the catalysts as highly dispersed vanadia supported by anatase titania with acidic sites of significant strength and density. The catalysts also showed very high stability with lifetime exceeding 4500 h. Extensive density functional theory calculations using both cluster and surface models revealed MF to form via the hemiacetal mechanism, involving the condensation of methanol and formaldehyde at acidic sites and methanol and hemiacetal oxidations at redox sites. The alternative formyl mechanism was predicted kinetically much less favorable, showing these catalysts to work in a distinct mechanism from the rutile titania photocatalyst. Interestingly, methanol chemisorption at redox sites leads to the formation of acidic sites capable of catalyzing the condensation reaction.

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Hierarchical SAPO-34 crystals were synthesized by a facile TEAOH etching post-treatment for the first time.

Single-atom catalysts (SACs) are getting more attention in the field of electrochemical energy storage and conversation, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), due to their welldefined active centers, tunable electron structure, maximum atom-utilization efficiency, and excellent durability. [1] Pyrolysis of metal-containing precursors is one of the most frequent approaches for SACs preparation. [2] With the atomic dispersion of catalysts, however, the increasing surface free energy results in atom aggregation to form metal clusters or nanoparticles in the thermal treatment. [3] Therefore, it is a challenge to obtain SACs with a high loading rate of metal via pyrolysis. Wei et al. synthesized atomic Zn (9.3 wt%) by adopting a low annealing rate method. [4a] Jiang et al. reported a high loading Zn atoms (11.3 wt%) supported on the N-doped hollow carbon derived from ZIF-8 covered polystyrene nanospheres. [4b] Additionally, Wan et al. developed a cascade anchoring strategy to obtain SACs with a 12.1 wt% metal loading rate [4c] and Huang et al. fabricated Co atoms (15.3 wt%) on graphenelike carbons by a salt-template method. [3c] However, developing a high atomic density is still under further exploration. Compared with the solo single-atom sites, dual-metal active sites have been demonstrated to have higher catalytic activity and selectivity for ORR. [5] Nevertheless, it is difficult to build the interaction between the dual-metal sites even on the same carbon support, because the low-density distribution of metal atoms resulted in the long distance between each other, and thus trended into isolated sites rather than synergistic sites. Therefore, developing carbon supports with highly dense atom distribution is the potential to provide a template to construct dual-metal active sites with synergistic roles.

Constructing heterostructures of covalent organic frameworks (COFs) and metal organic frameworks (MOFs) have gained great attention for various applications due to their well-defined skeletons, ordered porosity and designable functions. Herein,...