In Situ Porphyrin Substitution in a Zr(IV)‐MOF for Stability Enhancement and Photocatalytic CO₂ Reduction

Abstract

Despite numerous inherent merits of metal-organic frameworks (MOFs), structural fragility has imposed great restrictions on their wider involvement in many applications, such as in catalysis. Herein, a strategy for enhancing stability and enabling functionality in a labile Zr(IV)-MOF has been proposed by in situ porphyrin substitution. A size-and geometry-matched robust linear porphyrin ligand 4,4′-(porphyrin-5,15-diyl)dibenzolate (DCPP 2− ) is selected to replace the 4,4′-(1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-2,7(1H,3H,6H,8H)-diyl)dibenzoate (NDIDB 2− ) ligand in the synthesis of BUT-109(Zr), affording BUT-110 with varied porphyrin contents. Compared to BUT-109(Zr), the chemical stability of BUT-110 series is greatly improved. Metalloporphyrin incorporation endows BUT-110 MOFs with high catalytic activity in the photoreduction of CO 2 , in the absence of photosensitizers. By tuning the metal species and porphyrin contents in BUT-110, the resulting BUT-110-50%-Co is demonstrated to be a good photocatalyst for selective CO 2 -to-CO reduction, via balancing the chemical stability, photocatalytic efficiency, and synthetic cost. This work highlights the advantages of in situ ligand substitution for MOF modification, by which uniform distribution and high content of the incoming ligand are accessible in the resulting MOFs.More importantly, it provides a promising approach to convert unstable MOFs, which mainly constitute the vast MOF database but have always been neglected, into robust functional materials.

Porphyrin and phthalocyanine: from molecular materials to aggregates

“…此外还具有暴露的金属活性位点、氧化还原特性 [20,103,122,123] 。近年来，卟啉、酞菁作为催化剂和光敏剂 被广泛应用于光催化析氢 [124,125] 、光催化降解 [19,126] 、 光催化 CO2 还原 [127] 、光催化水氧化 [128] 等光催化反 应。其次，合成的卟啉、酞菁纳米材料往往具有大的 比表面积，形貌可控，光物理性能良好等特点。卟 啉、酞菁特殊的堆叠方式使得这些金属有机材料呈现 出了一种高度多孔的纳米结构。这种纳米多孔结构有 利于化学活性位点的充分暴露，能够促进催化剂与反 应介质的充分接触，有利于反应物与产物的快速扩 散。受自然界血红素铁卟啉位点参与生物 ORR 反应的 启发，具有 M-N 4 结构的化合物得到了科学家们的深 入研究。卟啉、酞菁主要是由不同的中心金属离子和 大环配体构成，具有结构灵活可调性，形成的 M-N 4 结构可以作为明确的活性位点参与催化反应 [129] 。酞 菁自 1964 年 Jasinski 等人 [130] 首次发现在燃料电池 中具有优异的催化性能之后，被普遍认为是最有效的 ORR 催化剂之一 [26,131,132] 。在众多催化应用中，卟 啉、酞菁催化性能的优化主要通过官能团化、中心金 属调控，轴向配位，π-π相互作用等策略与其他材 料复合，例如金属有机框架(MOFs) 、共价有机聚合 物(COFs)、石墨烯、石墨炔(GDY)等 [133][134][135] 。本部分， 主要关注的是卟啉、酞菁纳米材料近三年来利用各种…”

State‐of‐the‐Art Advancements in Photocatalytic Hydrogenation: Reaction Mechanism and Recent Progress in Metal‐Organic Framework (MOF)‐Based Catalysts

“…By combining the merits of porphyrin and MOFs, the porphyrin MOFs possess great application potential in photocatalysis. [ 127 ] The semiconductor‐like PCN‐222, a porphyrinic MOF, has been deliberately employed for effective enriching and converting CO 2 to HCOO − upon visible light irradiation. [ 103 ] The ultrafast spectroscopy together with time‐resolved photoluminescence spectroscopy unveil the existence of a deep electron trap state in PCN‐222, which enabled the catalyst to supply long‐lifetime electrons for CO 2 reduction.…”

Integrating boron atoms into ultrathin organic polymer for visible light photocatalytic CO2reduction to CH4with nearly 100% selectivity

“…26,27 For instance, metalloporphyrin or metallophthalocyanine-based organic polymers with M-N 4 (M ¼ Co, Ni, Cu, and Fe) active sites have been extensively employed for electro-/photocatalytic CO 2 reduction. [28][29][30] Graphite carbon nitride-supported metal active sites (Cu, Co, Fe, etc.) have also proven to be an effective strategy.…”