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The selective conversion of dilute NO pollutant into low-toxic product and simultaneous storage of metabolic nitrogen for crop plants remains a great challenge from the perspective of waste management and sustainable chemistry. This study demonstrates that this bottleneck can be well tackled by refining the reactive oxygen species (ROS) on Ni-modified NH 2 -UiO-66(Zr) (Ni@NU) using nickel foam (NF) as a three-dimensional (3D) substrate through a flow photoanode reactor via the gas-phase photoelectrocatalysis. By rationally refining the ROS to * OH, Ni@NU/NF can rapidly eliminate 82 % of NO without releasing remarkable NO 2 under a low bias voltage (0.3 V) and visible light irradiation. The abundant mesoporous pores on Ni@NU/NF are conducive to the diffusion and storage of the formed nitrate, which enables the progressive conversion NO into nitrate with selectivity over 99 % for long-term use. Through calculation, 90 % of NO could be recovered as the nitrate species, indicating that this state-of-the-art strategy can capture, enrich and recycle the pollutant N source from the atmosphere. This study offers a new perspective of NO pollutant treatment and sustainable nitrogen exploitation, which may possess great potential to the development of highly efficient air purification systems for industrial and indoor NO x control.

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Designing adsorption materials with high adsorption capacities and selectivities is highly desirable for precious metal recovery. Desorption performance is also particularly crucial for subsequent precious metal recovery and adsorbent regeneration. Herein, a metalorganic framework (MOF) material (NH 2 -UiO-66) with an asymmetric electronic structure of the central zirconium oxygen cluster has an exceptional gold extraction capacity of 2.04 g g À 1 under light irradiation. The selectivity of NH 2 -UiO-66 for gold ions is up to 98.8 % in the presence of interfering ions. Interestingly, the gold ions adsorbed on the surface of NH 2 -UiO-66 spontaneously reduce in situ, undergo nucleation and growth and finally achieve the phase separation of highpurity gold particles from NH 2 -UiO-66. The desorption and separation efficiency of gold particles from the adsorbent surface reaches 89 %. Theoretical calculations indicate that -NH 2 functions as a dual donor of electrons and protons, and the asymmetric structure of NH 2 -UiO-66 leads to energetically advantageous multinuclear gold capture and desorption. This adsorption material can greatly facilitate the recovery of gold from wastewater and can easily realize the recycling of the adsorbent.

Gold and palladium are the most widely used precious metal materials in the field of electronic devices and industrial catalysis. How to realize the green recycling of gold and palladium is important and challenging. In this work, we found that gold and palladium in wastes, such as electronic devices and industrial catalysts, can be completely dissolved and recycled by photocatalysis. Gold and palladium are oxidized to the ionic state in water, which does not involve strong acids, strong alkalis, toxic cyanides, or an organic medium. More interestingly, the dissolution of gold and palladium in different halogen aqueous solutions has special selectivity, which depends on the coordination stability constants between gold and palladium with halide ions. Therefore, gold and palladium can be selectively dissolved in iodine ion solution and bromine ion solution, respectively, then gold and palladium can be obtained by a one-step reduction. This work opens up a new direction for optimizing the photocatalytic dissolution technology and promoting the green recycling of precious metals.

The gas–water interface plays an important role in the photocatalytic degradation of volatile organic compounds (VOCs). Herein, a novel photocatalytic reactor with a tunable gas–water interface was designed and utilized to investigate the performance of photocatalytic degradation of VOCs. The relationship between the key operating parameters of the reactor and VOCs mineralization was investigated in detail with toluene as a model pollutant. The results showed that a tunable gas–water interface was formed in the process of atomized spray photocatalytic oxidation. Furthermore, the photocatalyst was easily excited by light, generating more free radicals, which was conducive to improving the mineralization performance of toluene and the durability of the catalyst. The intermediates of the toluene reaction were analyzed by photoacoustic spectroscopy (PAS), total organic carbon (TOC), and electrospray ionization–ion trap mass spectrometry (ESI–MS). The results show that abundant hydroxyl radicals are formed at the gas–water interface, which is beneficial to the opening of the benzene ring and greatly reduces the formation of toxicity and byproducts. Simultaneously, we investigated the degradation performance of acetone, formaldehyde, and n-hexane in the reactor. This provides a new strategy for using photocatalytic technology to purify industrial flue gas and indoor air.

NH2-UIO66 (NU) is a promising photocatalyst for the reduction of Cr(VI) to low-toxic Cr(III) driven by visible light under ambient conditions. However, the main limitation in this process is the inefficient ligand to metal charge transfer (LMCT) of photo-excited electrons, which is caused by inherent energy gap (ΔELMCT). This study synthesized the defective NU (NUX-H, where X is the molar equivalent of the modulator) with reduced ΔELMCT through linkers removal via acid treatment. The electronic structure of NUX-H was systematically investigated, and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms. Furthermore, they substantially lowered the energy of the unoccupied d orbitals (LUMO), which was beneficial to efficient LMCT, resulting in an improved photocatalytic activity of NUX-H toward high-concentration (100 mg/L) Cr(VI) reduction. Compared to NU with defect-free structure, the reducing rate of Cr(VI) was increased by 47 times. This work introduced an alternative strategy in terms of designing efficient photocatalysts for reducing Cr(VI) under ambient conditions.

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