Amine-Based MOF for Precious Metal Remediation.

Due to the continuous growth rate of the electronic industry, hi-tech companies depend on mining and extracting precious metals to meet the public demand. The high turnover of modern devices generates an alarming amount of electronic waste (e-waste), which contains more precious metals than mined ores and therefore needs efficient recovery procedures. A highly stable homopiperazine-derived Cd-MOF, poly-[Cd(H2L)]·9H2O, with a protonated amine ligand core, exists as a twofold interpenetrated 3D framework with 1D channels into which the N+-H bond is directed. The geometry of these channels appears to be suitable to host square planar metalate complexes. Under acidic conditions, [MCl4]x- anions containing Au, Cu, Ni, and Pt, representing common components of e-waste under extraction conditions, were tested for capture and recovery. Cd-MOF exhibits remarkable selectivity and uptake performance toward Au with an adsorbent capacity of 25 mg g-1ads and shows a marked selectivity for Au over Cu in competitive experiments. The adsorption mechanism of Au appears to be predominantly physical adsorption at the surface of the material.

Spontaneous Formation of a Ligand-Based 2D Capping Layer on the Surface of Quasi-2D Perovskite Films.

Two-dimensional (2D) Ruddlesden-Popper phase perovskites (RPPs) are attracting growing attention for photovoltaic applications due to their enhanced stability compared to three-dimensional (3D) perovskites. The superior tolerance of 2D RPPs films to moisture and oxygen is mainly attributed to the hydrophobic nature of the introduced long-chain spacer cations (ligands). In this work, it is revealed that a thin capping layer, consisting of self-assembled butylammonium ligands, is spontaneously formed on the top surface of a quasi-2D perovskite film prepared by conventional one-step hot casting. Based on morphological and crystallographic analyses of both the top/bottom surfaces and the interior of quasi-2D perovskite films, the formation process of the 2D capping layer and the assembly of RPPs, comprising both large and small slab thickness (large-n, small-n), is elucidated. The vertical orientation of RPPs that is required for sufficient charge transport for 2D perovskite solar cells (PSCs) is further verified. We propose that the surface capping layer is directly responsible for the long-term stability of 2D PSCs. This work provides detailed insight into the microstructure of quasi-2D RPPs films that should assist the development of strategies for unlocking the full potential of 2D perovskites for high-performance PSCs and other solid-state electronic devices.