The electrochemical reduction of CO2 presents a promising strategy to mitigate the greenhouse effect and reduce excess carbon dioxide emission to realize a carbon-neutral energy cycle, but it suffers from the lack of high-performance electrocatalysts. In this work, catalytic active cobalt porphyrin [TCPP(Co)=(5,10,15,20)-tetrakis(4-carboxyphenyl)porphyrin-CoII ] was precisely anchored onto water-stable 2D metal-organic framework (MOF) nanosheets (Zr-BTB) to obtain ultrathin 2D MOF nanosheets [TCPP(Co)/Zr-BTB] with accessible catalytic sites for the CO2 reduction reaction. Compared with molecular cobalt porphyrin, the TCPP(Co)/Zr-BTB exhibits an ultrahigh turnover frequency (TOF=4768 h-1 at -0.919 V vs. reversible hydrogen electrode, RHE) owing to high active-site utilization. In addition, three post-modified 2D MOF nanosheets [TCPP(Co)/Zr-BTB-PABA, TCPP(Co)/Zr-BTB-PSBA, TCPP(Co)/Zr-BTB-PSABA] were obtained, with the modifiers of p-(aminomethyl)benzoic acid (PABA), p-sulfobenzoic acid potassium (PSBA), and p-sulfamidobenzoic acid (PSABA), to change the micro-environments around TCPP(Co) through the tuning of steric effects. Among them, the TCPP(Co)/Zr-BTB-PSABA exhibited the best performance with a faradaic efficiency (FECO ) of 85.1 %, TOF of 5315 h-1 , and jtotal of 6 mA cm-2 at -0.769 V (vs. RHE). In addition, the long-term durability of the electrocatalysts is evaluated and the role of pH buffer is revealed.

中文翻译：

---

二维具有钴卟啉的金属-有机骨架纳米片，用于高效CO2电还原。

CO 2的电化学还原是减轻温室效应和减少过量二氧化碳排放以实现碳中性能量循环的一种有前途的策略，但是它缺乏高性能的电催化剂。在这项工作中，催化活性钴卟啉[TCPP（Co）=（5,10,15,20）-四（4-羧基苯基）卟啉-CoII]精确锚定在水稳定的2D金属-有机骨架（MOF）纳米片上（Zr-BTB）以获得超薄的二维MOF纳米片[TCPP（Co）/ Zr-BTB]，具有可用于CO2还原反应的催化位点。与分子钴卟啉相比，由于活性位点利用率高，TCPP（Co）/ Zr-BTB与可逆氢电极（RHE）相比，具有超高的转换频率（TOF = 4768 h-1 at -0.919 V）。此外，三个后修饰的2D MOF纳米片[TCPP（Co）/ Zr-BTB-PABA，获得了TCPP（Co）/ Zr-BTB-PSBA，TCPP（Co）/ Zr-BTB-PSABA]，对-（氨基甲基）苯甲酸（PABA），对-磺基苯甲酸钾（PSBA）和对氨基磺酰苯甲酸（PSABA），可通过调整空间效应来改变TCPP（Co）周围的微环境。其中，TCPP（Co）/ Zr-BTB-PSABA以-5.169 V（vs）的法拉第效率（FECO）为85.1％，TOF为5315 h-1，总电流为6 mA cm-2表现出最佳性能。 （RHE）。另外，评估了电催化剂的长期耐久性并揭示了pH缓冲剂的作用。其中，TCPP（Co）/ Zr-BTB-PSABA以-5.169 V（vs）的法拉第效率（FECO）为85.1％，TOF为5315 h-1，总电流为6 mA cm-2表现出最佳性能。 （RHE）。另外，评估了电催化剂的长期耐久性并揭示了pH缓冲剂的作用。其中，TCPP（Co）/ Zr-BTB-PSABA以-5.169 V（vs）的法拉第效率（FECO）为85.1％，TOF为5315 h-1，总电流为6 mA cm-2表现出最佳性能。 （RHE）。另外，评估了电催化剂的长期耐久性并揭示了pH缓冲剂的作用。