Transformation of CO2 into value-added chemicals with efficient and recyclable catalyst is an effective way to reduce carbon emissions. It is valuable to develop an efficient catalyst that can promote the N-formylation reaction under mild conditions with a high activity and excellent recyclability. Single atom catalysts (SACs) possess ultimate atom utilization efficiency and outstanding catalytic performance. Herein, we synthesize Zn SACs (Zn-TpPa) anchored on a COF (TpPa-1) using a facile solution method. Catalyzed by Zn-TpPa, CO2 and N-methylamine are transformed into N-methylformanilide under mild reaction conditions with a TOF of 17,155 h−1, which is the highest among all reported recyclable Zn-based catalysts. Zn-TpPa can also catalyze N-formylation of many other amines with excellent yields. The higher reactivity was attributable to the well-dispersed Zn active sites on COF and outstanding adsorption of CO2 owing to high surface area of COF. Our research provides a facile method for constructing SACs as well as an effective pathway for CO2 transformation and environmental protection. Graphical abstract Zn Single atom catalysts anchored on COF (TpPa-1) are prepared in a facile method and characterized. Zn-TpPa promotes N-formylation of N-methylaniline with CO2 and phenylsilane under mild conditions with the highest TOF among all reported recyclable Zn-catalysts. Besides, Zn-TpPa can catalyze N-formylation of many other amines with excellent yields. The work provides a facile method for constructing SACs. Download : Download high-res image (217KB) Download : Download full-size image Introduction Carbon dioxide (CO2), known as the main factor for green-house effect, has stimulated much effort to develop efficient technologies and methods for decreasing the CO2 level in the atmosphere. [[1], [2], [3], [4], [5]] As CO2 is a non-toxic, abundant, renewable C1 building block, easily available and environmentally benign feedstock, in view of green and sustainable chemistry, designing recyclable catalysts for the transformation of CO2 into value-added chemicals has recently emerged as an attractive route. [[6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23]] One interesting route to fix CO2 is synthesis of formamides through N-formylation of amines using CO2 in the presence of reducing agent. Many catalysts were reported to promote this reaction. [10,16,[24], [25], [26], [27], [28], [29], [30]] However, those reported N-formylation catalysis either have a limited turnover frequency (TOF) [21,[31], [32], [33], [34], [35], [36]] or require harsh conditions, such as high reaction temperatures (>60 °C) [7,15,21,25,34,[36], [37], [38]] or high CO2 pressure (>1 Mpa) [6,7,[13], [14], [15],21,32,33,[37], [38], [39], [40]] and poor recyclability [35]. It is highly desirable to develop an efficient catalyst that can promote the N-formylation reaction under mild conditions with a high TOF and excellent recyclability. Single-atom catalysts (SACs), containing single metal atoms anchored on solid supports, represent the utmost utilization of metallic catalysts and thus maximize catalytic reactivity. [[41], [42], [43], [44], [45]] Several fabrication processes for SACs have been reported [46], including atomic layer deposition, [47] wet chemistry [48], MOF derivative [49], potential cycling [50], acid leaching [51] and photodeposition [52]. However, they usually either require harsh conditions, such as high temperature, high pressure, acids or complicated reaction procedures. Considering the large-scale production in future industrialization, a simple and efficient way to achieve SACs is more favorable. An appropriate support is critical to interact strongly with isolated atoms, and thus prevents the movement and aggregation of isolated atoms [[53], [54], [55]], creating stable, finely dispersed active sites. Covalent organic frameworks (COFs) represent an important type of covalent porous materials with high surface area and well-defined structures. [56,57] The periodic and permanent porosity endow COFs an excellent substrate for SACs [58]. The bottom-up synthesis using different building blocks endows COFs with tunable skeleton structure, pore size, and topology schemes [53,59,60]. With the bottom-up synthesis of COFs followed by post-metalation, it offers unprecedented opportunities for constructing SACs with well-defined catalytic centers in high metal loading [61]. Herein, we demostrate Zn single atom catalyts can be prepared on COF (TpPa-1) with high loading amount by facile dropwise adding Zn2+ solution into TpPa-1 suspension (Scheme 1) [62,63]. Catalyzed by Zn-TpPa, N-methylformanilide is produced by reacting N-methylaniline with CO2 and hydrosilanes under mild reaction conditions (1 bar CO2 pressure at room temperature) in 3 h with a TOF of 17,155 h−1, which is the highest among reported recyclable Zn-based catalysts. Besides, Zn-TpPa could catalyze N-formylation of many other amines with excellent yields. Our research provides a simple yet efficient method for constructing SACs as well as provides an effective and sustainable pathway for CO2 transformation and environmental protection. Section snippets Materials and characterizations 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-1) were purchased from Shanghai Macklin Biochemical Co. Ltd. N-methylaniline, aniline, p-toluidine, N-methyl-p-toluidine, 4-methoxy-N-methylaniline, 4-bromo-N-methylaniline, N-methylcyclohexylamine, diethylamine, pyrrolidine, morpholine, 1,2,3,4-Tetrahydro-1-methylquinoline, and phenylsilane were obtained from J&K Scientific Ltd. N, N-dimethylformamide, acetonitrile mesitylene, dioxane and methanol were obtained from Aladdin Characterization of materials We synthesized single atom catalysts Zn-TpPa by adding the aqueous Zn salt solution into TpPa-1 suspension (Scheme 1), which was synthesized according to the method as previously reported. [62,63] The composition of TpPa-1 and Zn-TpPa was assessed with X-ray photoelectron spectroscopy. The peaks at 1020 eV and 1045 eV in Zn 2p XPS (Fig. S1d) spectrum indicated the presence of Zn element in Zn-TpPa. Besides, the Zn loading in the Zn-TpPa reached 0.5 wt%, as determined by inductively coupled Conclusion In conclusion, Zn single atom catalyst on COF with high loading were facially prepared. Zn-TpPa showed excellent catalyst activity, selectivity and recyclability for N-formation under mild condition with CO2 and phenysilane. It showed the highest TOF normalized to single Zn sites as 17,155 h−1 among all reported Zn-based catalysts. Importantly, Zn-TpPa showed the highest TOF among all reported catalysts which promoted N-formylation of N-methylaniline with CO2 and hydrosilanes with good CRediT authorship contribution statement Qiang Cao: Investigation, Conceptualization, Writing - original draft. Long-Long Zhang: Data curation. Chang Zhou: Resources. Jing-Hui He: Supervision, Writing - review & editing, Funding acquisition. Antonio Marcomini: Writing - review & editing. Jian-Mei Lu: Resources, Writing - review & editing, Supervision, Funding acquisition. Declaration of Competing Interest The authors report no declarations of interest. Acknowledgements We gratefully acknowledge the financial support provided by National Natural Science Foundation of China (21978185, 21938006, 21776190), the National Key R&D Program of China (2020YFC1818401, 2017YFC0210906), Basic Research Project of Leading Technology in Jiangsu Province (BK20202012), Suzhou Science and Technology Bureau Project (SYG201935) and the project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Covalent organic framework-supported Zn single atom catalyst for highly efficient N-formylation of amines with CO2 under mild conditions

Antonio Marcomini;
2021-01-01

Abstract

Transformation of CO2 into value-added chemicals with efficient and recyclable catalyst is an effective way to reduce carbon emissions. It is valuable to develop an efficient catalyst that can promote the N-formylation reaction under mild conditions with a high activity and excellent recyclability. Single atom catalysts (SACs) possess ultimate atom utilization efficiency and outstanding catalytic performance. Herein, we synthesize Zn SACs (Zn-TpPa) anchored on a COF (TpPa-1) using a facile solution method. Catalyzed by Zn-TpPa, CO2 and N-methylamine are transformed into N-methylformanilide under mild reaction conditions with a TOF of 17,155 h−1, which is the highest among all reported recyclable Zn-based catalysts. Zn-TpPa can also catalyze N-formylation of many other amines with excellent yields. The higher reactivity was attributable to the well-dispersed Zn active sites on COF and outstanding adsorption of CO2 owing to high surface area of COF. Our research provides a facile method for constructing SACs as well as an effective pathway for CO2 transformation and environmental protection. Graphical abstract Zn Single atom catalysts anchored on COF (TpPa-1) are prepared in a facile method and characterized. Zn-TpPa promotes N-formylation of N-methylaniline with CO2 and phenylsilane under mild conditions with the highest TOF among all reported recyclable Zn-catalysts. Besides, Zn-TpPa can catalyze N-formylation of many other amines with excellent yields. The work provides a facile method for constructing SACs. Download : Download high-res image (217KB) Download : Download full-size image Introduction Carbon dioxide (CO2), known as the main factor for green-house effect, has stimulated much effort to develop efficient technologies and methods for decreasing the CO2 level in the atmosphere. [[1], [2], [3], [4], [5]] As CO2 is a non-toxic, abundant, renewable C1 building block, easily available and environmentally benign feedstock, in view of green and sustainable chemistry, designing recyclable catalysts for the transformation of CO2 into value-added chemicals has recently emerged as an attractive route. [[6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23]] One interesting route to fix CO2 is synthesis of formamides through N-formylation of amines using CO2 in the presence of reducing agent. Many catalysts were reported to promote this reaction. [10,16,[24], [25], [26], [27], [28], [29], [30]] However, those reported N-formylation catalysis either have a limited turnover frequency (TOF) [21,[31], [32], [33], [34], [35], [36]] or require harsh conditions, such as high reaction temperatures (>60 °C) [7,15,21,25,34,[36], [37], [38]] or high CO2 pressure (>1 Mpa) [6,7,[13], [14], [15],21,32,33,[37], [38], [39], [40]] and poor recyclability [35]. It is highly desirable to develop an efficient catalyst that can promote the N-formylation reaction under mild conditions with a high TOF and excellent recyclability. Single-atom catalysts (SACs), containing single metal atoms anchored on solid supports, represent the utmost utilization of metallic catalysts and thus maximize catalytic reactivity. [[41], [42], [43], [44], [45]] Several fabrication processes for SACs have been reported [46], including atomic layer deposition, [47] wet chemistry [48], MOF derivative [49], potential cycling [50], acid leaching [51] and photodeposition [52]. However, they usually either require harsh conditions, such as high temperature, high pressure, acids or complicated reaction procedures. Considering the large-scale production in future industrialization, a simple and efficient way to achieve SACs is more favorable. An appropriate support is critical to interact strongly with isolated atoms, and thus prevents the movement and aggregation of isolated atoms [[53], [54], [55]], creating stable, finely dispersed active sites. Covalent organic frameworks (COFs) represent an important type of covalent porous materials with high surface area and well-defined structures. [56,57] The periodic and permanent porosity endow COFs an excellent substrate for SACs [58]. The bottom-up synthesis using different building blocks endows COFs with tunable skeleton structure, pore size, and topology schemes [53,59,60]. With the bottom-up synthesis of COFs followed by post-metalation, it offers unprecedented opportunities for constructing SACs with well-defined catalytic centers in high metal loading [61]. Herein, we demostrate Zn single atom catalyts can be prepared on COF (TpPa-1) with high loading amount by facile dropwise adding Zn2+ solution into TpPa-1 suspension (Scheme 1) [62,63]. Catalyzed by Zn-TpPa, N-methylformanilide is produced by reacting N-methylaniline with CO2 and hydrosilanes under mild reaction conditions (1 bar CO2 pressure at room temperature) in 3 h with a TOF of 17,155 h−1, which is the highest among reported recyclable Zn-based catalysts. Besides, Zn-TpPa could catalyze N-formylation of many other amines with excellent yields. Our research provides a simple yet efficient method for constructing SACs as well as provides an effective and sustainable pathway for CO2 transformation and environmental protection. Section snippets Materials and characterizations 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-1) were purchased from Shanghai Macklin Biochemical Co. Ltd. N-methylaniline, aniline, p-toluidine, N-methyl-p-toluidine, 4-methoxy-N-methylaniline, 4-bromo-N-methylaniline, N-methylcyclohexylamine, diethylamine, pyrrolidine, morpholine, 1,2,3,4-Tetrahydro-1-methylquinoline, and phenylsilane were obtained from J&K Scientific Ltd. N, N-dimethylformamide, acetonitrile mesitylene, dioxane and methanol were obtained from Aladdin Characterization of materials We synthesized single atom catalysts Zn-TpPa by adding the aqueous Zn salt solution into TpPa-1 suspension (Scheme 1), which was synthesized according to the method as previously reported. [62,63] The composition of TpPa-1 and Zn-TpPa was assessed with X-ray photoelectron spectroscopy. The peaks at 1020 eV and 1045 eV in Zn 2p XPS (Fig. S1d) spectrum indicated the presence of Zn element in Zn-TpPa. Besides, the Zn loading in the Zn-TpPa reached 0.5 wt%, as determined by inductively coupled Conclusion In conclusion, Zn single atom catalyst on COF with high loading were facially prepared. Zn-TpPa showed excellent catalyst activity, selectivity and recyclability for N-formation under mild condition with CO2 and phenysilane. It showed the highest TOF normalized to single Zn sites as 17,155 h−1 among all reported Zn-based catalysts. Importantly, Zn-TpPa showed the highest TOF among all reported catalysts which promoted N-formylation of N-methylaniline with CO2 and hydrosilanes with good CRediT authorship contribution statement Qiang Cao: Investigation, Conceptualization, Writing - original draft. Long-Long Zhang: Data curation. Chang Zhou: Resources. Jing-Hui He: Supervision, Writing - review & editing, Funding acquisition. Antonio Marcomini: Writing - review & editing. Jian-Mei Lu: Resources, Writing - review & editing, Supervision, Funding acquisition. Declaration of Competing Interest The authors report no declarations of interest. Acknowledgements We gratefully acknowledge the financial support provided by National Natural Science Foundation of China (21978185, 21938006, 21776190), the National Key R&D Program of China (2020YFC1818401, 2017YFC0210906), Basic Research Project of Leading Technology in Jiangsu Province (BK20202012), Suzhou Science and Technology Bureau Project (SYG201935) and the project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/5036142
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