Self-adaptive dual-metal-site pairs in metal-organic frameworks for selective CO2 photoreduction to CH4
Release time：2021-09-09 Views：101
Jian Li1,3, Hongliang Huang 1,3, Wenjuan Xue1,3, Kang Sun2,3, Xiaohui Song1 , Chunrui Wu1 , Lei Nie 1 , Yang Li1 , Chengyuan Liu2 , Yang Pan2 , Hai-Long Jiang 2 ✉, Donghai Mei 1 ✉ and Chongli Zhong 1 ✉
Solar-light-driven reduction of CO2-to-CH4 is a complex process involving multiple elementary reactions and various by-products. Achieving high CH4 activity and selectivity therefore remain a significant challenge. Here we show a bioinspired photocatalyst with flexible dual-metal-site pairs (DMSPs), which exhibit dynamic self-adaptive behaviour to fit mutative C1 intermediates, achieving CO2-to-CH4 photoreduction. The Cu and Ni DMSPs in their respective single-site forms under flexible microenvironment are incorporated into a metal-organic framework (MOF) to afford MOF-808-CuNi. This dramatically boosts CH4 selectivity up to 99.4% (electron basis) and 97.5% (product basis), and results in a high production rate of 158.7 μmol g−1 h−1 with a sacrificial reagent. Density functional theory calculations reveal that the flexible self-adaptive DMSPs can stabilize various C1 intermediates in multistep elementary reactions, leading to highly selective CO2-to-CH4 process. This work demonstrates that efficient and selective heterogeneous catalytic processes can be achieved by stabilizing reaction intermediates via the self-adaptive DMSP mechanism.
Photocatalytic CO2 reduction measurements. Here, 25mg of photocatalyst powder and 50mg (molar concentration 1.3mM) of [Ru(bpy)3]Cl2•6H2O were mixed in a 50-ml solution containing 30ml of acetonitrile, 10ml of TEOA and 10ml of H2O in a 250-ml quartz reaction cell. The CO2 (purity >99.999%) was purged into this reaction cell for 0.5h to eliminate the dissolved oxygen. Before illumination, the reactor was installed to CEL-SPH2N system (Beijing China Education Au-light Co., Ltd) equipped with a 300-W Xe lamp with the 420-nm cutoff filter (420nm<λ<760nm). On degassing,the system was filled with CO2 (purity >99.999%) to 1 atm. For photocatalytic CO and HCOOH reduction measurements, 10ml of CO (99.999%) or 1ml of liquid HCOOH was injected into photocatalytic system. Subsequently, the Ar as the packed gas was purged into the system to reach atmospheric pressure. Gas chromatography (Agilent 7890B) was applied to analysed gaseous products by the detectors of a thermal conductivity detector and a flame ionization detector using Ar as the carrier gas. The HCOOH in the liquid phase was analysed using ion chromatography (Thermo ICS-5000). The possible alcohol products were detected by a liquid chromatogram (Waterse 2695), and no related signals could be observed. The catalytic results were repeated three times with three batches of catalysts to give more reliable data. Gas chromatography– mass spectrometry (Bruker solanX 70 FT-MS) was applied to analyse the isotope labelled products using 13CO2 as the feed gas. The light intensity data were measured using a PM100D optical power meter (Thorlabs) equipped with a S425C detector (Supplementary Table 9). The heterogeneity test was performed by removing the catalyst from the reaction medium at 6h by centrifugation49.
Download:Nature Catalysis 2021, 4, 719–729 MOF-808-CuNi CO2RR.pdf