Recovering noble metals from waste streams using porous organic frameworks for heterogeneous catalysis

Recovering noble metals from waste resources and incorporating them into catalysts stands out as a promising strategy for advancing sustainability within the catalysis field. This review provides a comprehensive overview of recent investigations into noble metal recovery from waste streams, specifically employing porous organic frameworks(POFs). Additionally, the study delves into the utilization of the resultant composites, enriched with noble metals, in heterogeneous catalysis. Moreover, we offer insights into the challenges faced and outline prospects for the practical implementation of extracting noble metal catalysts from waste streams using POFs, aiming to develop cost-effective, sustainable, and efficient heterogeneous catalysts.

Drawing highly ordered MXene fibers from dynamically aggregated hydrogels

Assembly of two-dimensional (2D) nanomaterials into well-organized architectures is pivotal for controlling their function and enhancing performance. As a promising class of 2D nanomaterials, MXenes have attracted significant interest for use in wearable electronics due to their unique electrical and mechanical properties. However, facile approaches for fabricating MXenes into macroscopic fibers with controllable structures are limited. In this study, we present a strategy for easily spinning MXene fibers by incorporating polyanions. The introduction of poly(acrylic acid) (PAA) into MXene colloids has been found to alter MXene aggregation behavior, resulting in a reduced concentration threshold for lyotropic liquid crystal phase. This modification also enhances the viscosity and shear sensitivity of MXene colloids. Consequently, we were able to draw continuous fibers directly from the gel of MXene aggregated with PAA. These fibers exhibit homogeneous diameter and high alignment of MXene nanosheets, attributed to the shear-induced long-range order of the liquid crystal phase. Furthermore, we demonstrate proof-of-concept applications of the ordered MXene fibers, including textile-based supercapacitor, sensor and electrical thermal management, highlighting their great potential applied in wearable electronics. This work provides a guideline for processing 2D materials into controllable hierarchical structures by regulating aggregation behavior through the addition of ionic polymers.

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO_(2)capture

Utilizing solar energy for sorbent regeneration during the CO_(2)swing adsorption process could potentially reduce CO_(2)capture costs.This study describes a new technique—solar thermal swing adsorption(STSA)for CO_(2)capture based on application of intermittent illumination onto porous carbon monolith(PCM)sorbents during the CO_(2)capture process.This allows CO_(2)to be selectively adsorbed on the sorbents during the light-off periods and thereafter released during the light-on periods due to the solar thermal effect.The freestanding and mechanically strong PCMs have rich ultramicropores with narrow pore size distributions,displaying relatively high CO_(2)adsorption capacity and high CO_(2)/N_(2) selectivity.Given the high CO_(2)capture performance,high solar thermal conversion efficiency,and high thermal conductivity,the PCM sorbents could achieve high CO_(2)capture rate of up to 0.226 kg·kgcarbon^(-1)·h^(-1)from a gas mixture of 20 vol.%CO_(2)/80 vol.%N_(2) under STSA conditions with a light intensity of 1000 W·m^(-2).In addition,the combination of STSA with the conventional vacuum swing adsorption technique further increases the CO_(2)working capacity.

Polydopamine-based redox-active separators for lithium-ion batteries

The performance of lithium-ion batteries(LIBs)can be effectively enhanced with functionalized separators.Herein,it is demonstrated that polydopamine-based redox-active(PRA)separators can provide additional capacity to that of typical anode materials,increase the volumetric capacity of the cell,as well as,decrease the cell resistance to yield an improved performance at higher cycling rates.The PRA separators,which are composed of a 2 mm thick electrically insulating nanocellulose fiber(NCF)layer and an 18 mm thick polydopamine(PDA)and carbon nanotube(CNT)containing redox-active layer,are readily produced using a facile paper-making process.The PRA separators are also easily wettable by commonly employed electrolytes(e.g.LP40)and exhibit a high dimensional stability.In addition,the pore structure endows the PRA separator with a high ionic conductivity(i.e.1.06 mS cm^(-1))that increases the rate performance of the cells.Due to the presence of the redox-active layer,Li_(4)Ti_(5)O_(12)(LTO)half-cells containing PRA separator were found to exhibit significantly higher capacities than the corresponding cells containing commercial separators.These results clearly show that the implementation of this type of redox-active separators constitutes a straightforward and effective way to increase the energy and power densities of LIBs.