Ambient Chemical Fixation of CO 2 Using a Robust Ag 27 Cluster‐Based Two‐Dimensional Metal–Organic Framework

Metal-Thiolate Framework for Electrochemical and Photoelectrochemical Hydrogen Generation

Hydrogen has evolved as the cleanest and most sustainable fuel, produced directly from naturally abundant water resources. Generation of hydrogen by electrochemical or photoelectrochemical splitting of water has been conceived as the most effective method for hydrogen production. Herein, a robust solid metal-thiolate framework (MTF-1) was obtained by hydrothermal crystallization of the reaction mixture consisting of 1,3,5-triazine-2,4,6-trithioltrisodium salt and Cu^II under mild synthesis conditions. The material was thoroughly characterized and explored as efficient catalyst for electrochemical and photoelectrochemical hydrogen evolution reaction (HER) via water splitting reactions. MTF-1 showed onset potential 0.045 V_RHE and overpotential η(@10 mA cm^-2 ) at 0.096 V_RHE . The electrochemical surface area of MTF-1 was found to be 509 m²  g^-1 . The photo current density at pH 5.0 was found to be 0.487 mA cm^-2 at 0.6 V_RHE . The feasibility of the reaction pathway was correlated from the density function theory study, which suggested the complete downhill energetics indicating spontaneous electrochemical hydrogen generation in the acidic medium.

Highly Efficient Conversion of Propargylic Alcohols and Propargylic Amines with CO2 Activated by Noble-Metal-Free Catalyst Cu2 O@ZIF-8

The cyclization reactions of propargylic alcohols and propargylic amines with CO₂ are important in industrial applications, but it was a great challenge that non-noble-metal catalysts catalyzed both reactions under mild conditions. Herein, the catalyst Cu₂ O@ZIF-8 was prepared by encapsulating Cu₂ O nanoparticles into robust ZIF-8, and it can effectively catalyze the cyclization of both propargylic alcohols and propargylic amines with CO₂ into valuable α-alkylidene cyclic carbonates and oxazolidinones with turnover numbers (TONs) of 12.1 and 19.6, which can be recycled at least five times. The mechanisms were further uncovered by NMR, FTIR, ¹³ C isotope-labeling experiments and DFT calculations, in which Cu₂ O and DBU can synergistically activate the C≡C bond and the hydroxy/amino group of substrates. Importantly, it is the first example of a noble-metal-free catalyst that can catalyze both propargylic alcohols and propargylic amines with CO₂ simultaneously.

Precisely Constructed Silver Active Sites in Gold Nanoclusters for Chemical Fixation of CO2

Precise control of the composition and structure of active sites in an atom-by-atom fashion remains insuperable for heterogeneous catalysts. Here, we introduce tailor-made catalytic sites for the cycloaddition of CO₂ to epoxides achieved by implementing Ag atoms at different levels of liberation in atomically precise Au nanoclusters. Our results reveal that a single open Ag site on the Au₁₉ Ag₄ cluster improves the ring-opening of epoxides and sequent CO₂ insertion, while the partially exposed Ag site on the Au₂₀ Ag₁ cluster exhibits a weak affinity for epoxides and poor efficiency for CO₂ capture. Structural tunability imparted by the atom-by-atom tailoring and unusual atomic charges distributed on Au and Ag atoms of the three clusters seem to be crucial for promoting challenging bond cleavages and formations in the chemical utilization of CO₂ .