Reversible CO2 capture and release under ambient conditions is crucial for energy-efficient carbon capture and storage. Here, we report the pressure swing crystallization of CO2 in a single-crystalline guanidinium sulfate-based clathrate salt under practical conditions of 52 kPa and 298 K, with a high CO2 density (0.252 g cm
3 ) and capacity (17 wt %). The captured CO2 is released as a pure stream through moderate means of pressure or temperature stimulation, all while the desorbed Gua2SO4 is ready for another cycle. The clathrate is selective exclusively to CO2 even in the presence of common flue gas components, such as water vapor and N2, owing to the specific electrostatic interaction between the CO2 and guanidinium cations. The mechanism unraveled through single-crystal studies is distinctively different from physisorption or chemisorption, opening up a promising venue for future carbon capture and storage technologies through rapid CO2 solidification using an abundant salt.

Catalytic ammonia decomposition enables ammonia to be a hydrogen gas carrier for a carbon-free fuel economy. The challenge is to obtain high conversion yields and rates at low temperatures for a prolonged time. A promising approach is to engineer a catalyst support to minimize deleterious effects like sintering. Here, we compared a conventional 2D planar porous framework support with a vertically standing 2D structure to ascertain the effects of support geometry on the catalytic performance. The catalysts were made by loading ruthenium (Ru) nanoparticles onto the structures, and the catalytic activities were monitored by varying the ammonia (NH3) feeding rate and reaction temperature. Unlike the planar version, the vertically standing 2D support prevented nanoparticle aggregation, retained the original nanoparticle size, and showed an excellent hydrogen production rate (95.17 mmol gRu−1 min−1) at a high flow rate of 32,000 mL gcat−1 h−1 at a temperature of 450 °C.

Precious metals, particularly palladium (Pd), are in short supply, and their effective recovery from waste depends on metal-specific adsorbents that provide energy-efficient and environmentally friendly solutions. In this issue of Chem, Coskun and co-workers introduce a new porous organic polymer with exceptional porosity and stability and record-high capacity and selectivity toward Pd.

Our best option in curbing greenhouse gas emissions is to include heavy carbon emitters in a viable, sustainable, transitional solution based on a versatile syngas-based circular carbon economy and to establish a universal carbon emissions metric rather than fighting an endless war of politics, policies, and empty promises.

Interface engineering is a powerful strategy for modulating electronic structure and enhancing intrinsic activity of electrocatalysts for water splitting. Here, we grow two-dimensional cobalt-iron hydroxide (CoFe-OH) nanosheets on nickel foam substrates and deposit FeOOH nanoparticles in a rapid and scalable wet chemical approach. The CoFe-OH@FeOOH nanocomposite features abundant active sites and high surface area, allowing fast kinetics for electrochemical water splitting. The electrode has a low overpotential value of 200 mV at 50 mA cm−2 for oxygen evolution. When used as both anode and cathode for overall water splitting, CoFe-OH@FeOOH provides a low cell voltage of 1.56 V to deliver 10 mA cm−2 current density. The synergistic activity is presumed to be from the seamless interface of CoFe-OH and FeOOH, improving conductivity and mass transfer. We envision that this simple approach may offer a new direction for designing efficient electrodes for energy conversion applications.