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Developing solid porous materials into free-flowing liquids with permanent porosity is a promising strategy for overcoming certain limitations of conventional sorbent materials employed in gas storage and separation applications. The ability to control the pore size and chemical functionalities of organic frameworks gives these particular nanoporous materials distinct advantages over other small cage-like molecules or hollow particles that have been developed into porous liquids. In this paper, we describe the synthesis of a 3D imine-linked colloidal covalent organic framework (COF)-based porous liquid, designed for efficient size-exclusion of solvent, as well as for long-term stability. By tethering ionic liquids to themore » colloid surface, the colloids can be dried, purified, and resuspended in a variety of solvents without irreversible aggregation typically observed of COF colloids. Colloid size could be controlled between 50 and 400 nm, with surface areas as high as 800 m² g^–1. The 3D intertwining morphology of the colloids had pore sizes ranging from 5 to 14 Å, allowing them to efficiently size-exclude bulky ionic liquids. The COF colloids were stable towards flocculation in an ionic liquid for >1 year. Permanent porosity was confirmed with a combination of 19F NMR measurements and gas sorption techniques. CO₂ and CH₄ uptake in these porous liquids increased more than 10 and 20-fold, respectively, over non-porous, neat ionic liquid control samples. The work not only advances the state of COF-based colloid science but also represents a practical advance towards developing more robust, tunable framework-based porous liquid materials for a host of gas storage and separation applications.« less

While photoelectrochemical (PEC) solar-to-hydrogen efficiencies have greatly improved over the past few decades, advances in PEC durability have lagged behind. Corrosion of semiconductor photoabsorbers in the aqueous conditions needed for water splitting is a major challenge that limits device stability. In addition, a precious-metal catalyst is often required to efficiently promote water splitting. In this work, we demonstrate unassisted water splitting using a nonprecious metal molybdenum disulfide nanomaterial catalytic protection layer paired with a GaInAsP/GaAs tandem device. This device was able to achieve stable unassisted water splitting for nearly 12 h, while a sibling sample with a PtRu catalyst wasmore » only stable for 2 h, highlighting the advantage of the nonprecious metal catalyst. In situ optical imaging illustrates the progression of macroscopic degradation that causes device failure. Furthermore, this work compares unassisted water splitting devices across the field in terms of the efficiency and stability, illustrating the need for improved stability.« less

Copper(II) formate is efficiently incorporated into the pores of a 2D imine-based covalent organic framework (COF) via coordination with the phenol and imine groups. The coordinated metal ion is then reduced to Cu(I) with a thermal treatment that evolves CO₂. After loading with hydrogen gas, the majority of H₂ desorbs from the coordinatively saturated Cu(II) COF at temperatures < -100 degrees C. However, the activated Cu(I) COF retains adsorbed H₂ above room temperature. Adsorption/desorption of H₂ was highly reversible. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) strongly supports a molecular hydrogen interaction with Cu(I). A Kissinger analysis of variable rampmore » rate desorption experiments estimates the enthalpy of H₂ desorption from Cu(I) at 15 kJ mol^-1. The results represent an advance toward practical H₂ storage and delivery in a lightweight, stable, and highly versatile material.« less

Durable performance and high efficiency in solar-driven water splitting are great challenges not yet co-achieved in photoelectrochemical (PEC) cells. Although photovoltaic cells made from III–V semiconductors can achieve high optical–electrical conversion efficiency, their functional integration with electrocatalysts and operational lifetime remain great challenges. Herein, an ultra-thin TiN layer was used as a diffusion barrier on a buried junction n⁺p-GaInP₂ photocathode, to enable elevated temperatures for subsequent catalyst growth of Ni₅P₄ as nano-islands without damaging the GaInP₂ junction. The resulting PEC half-cell showed negligible absorption loss, with saturated photocurrent density and H₂ evolution equivalent to the benchmark photocathode decorated with PtRumore » catalysts. High corrosion-resistant Ni₅P₄/TiN layers showed undiminished photocathode operation over 120 h, exceeding previous benchmarks. Etching to remove electrodeposited copper, an introduced contaminant, restored full performance, demonstrating operational ruggedness. The TiN layer expands the synthesis conditions and protects against corrosion for stable operation of III–V PEC devices, while the Ni₅P₄ catalyst replaces costly and scarce noble metal catalysts.« less

Catalytic MoS_x thin films have been directly photoelectrodeposited on GaInP₂ photocathodes for stable photoelectrochemical hydrogen generation. Specifically, the MoSx deposition conditions were controlled to obtain 8-10 nm films directly on p-GaInP₂ substrates without ancillary protective layers. The films were nominally composed of MoS₂, with additional MoO_xS_y and MoO₃ species detected and showed no long-range crystalline order. The as-deposited material showed excellent catalytic activity toward the hydrogen evolution reaction relative to bare p-GaInP₂. Notably, no appreciable photocurrent reduction was incurred by the addition of the photoelectrodeposited MoSx catalyst to the GaInP₂ photocathode under light-limited operating conditions, highlighting the advantageous optical propertiesmore » of the film. The MoS_x catalyst also imparted enhanced durability toward photoelectrochemical hydrogen evolution in acidic conditions, maintaining nearly 85% of the initial photocurrent after 50 h of electrolysis. In total, this work demonstrates a simple method for producing dual-function catalyst/protective layers directly on high-performance, planar III-V photoelectrodes for photoelectrochemical energy conversion.« less