Zinc- and Copper-Loaded Nanosponges from Cellulose Nanofibers Hydrogels: New Heterogeneous Catalysts for the Synthesis of Aromatic Acetals.
Zinc- and Copper-Loaded Nanosponges from Cellulose Nanofibers Hydrogels: New Heterogeneous Catalysts for the Synthesis of Aromatic Acetals.
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DOI：
10.3390/gels8010054
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发表时间：
2022-01-12
期刊：
影响因子：
--
通讯作者：
Sacchetti A
中科院分区：
文献类型：
--
作者：
Riva L;Lotito AD;Punta C;Sacchetti A
本文报道了纤维素基金属负载纳米海绵的合成及其作为多相催化剂在有机合成中的应用。首先，将氧化纤维素纳米纤维(TOCNF)与支化聚乙烯亚胺(BPEI)和柠檬酸(CA)在水溶液中结合，并对所得水凝胶进行热处理，合成了生态安全的微孔和纳米孔纤维素纳米海绵(CNS)。随后，利用已经在环境净化领域得到广泛研究的CNS的金属络合特性，该材料成功地负载了铜(II)或锌(II)金属离子。通过扫描电子显微镜(SEM)和能量色散X射线能谱(EDS)分析以及电感耦合等离子体-光发射光谱(ICP-OES)分析，证实了金属负载的效率和均匀性。在芳香缩醛的合成中，芳香醛和醇之间的反应在有机合成中起着重要的中间体作用，所得到的材料作为多相催化剂具有很好的催化性能。优化的条件可以使转化率高于90%，对缩醛产物几乎完全有选择性，最大限度地减少，甚至在某些情况下消除了羧酸副产物的形成。对反应介质的电感耦合等离子体发射光谱分析可以排除任何可能的金属离子释放，证实催化是在多相条件下进行的。这种新型的负载金属的CNS可以重复使用和回收五次，而不会失去催化活性。
Herein we report the synthesis of cellulose-based metal-loaded nano-sponges and their application as heterogeneous catalysts in organic synthesis. First, the combination in water solution of TEMPO-oxidized cellulose nanofibers (TOCNF) with branched polyethyleneimine (bPEI) and citric acid (CA), and the thermal treatment of the resulting hydrogel, leads to the synthesis of an eco-safe micro- and nano-porous cellulose nano-sponge (CNS). Subsequently, by exploiting the metal chelation characteristics of CNS, already extensively investigated in the field of environmental decontamination, this material is successfully loaded with Cu (II) or Zn (II) metal ions. Efficiency and homogeneity of metal-loading is confirmed by scanning electron microscopy (SEM) analysis with an energy dispersive X-ray spectroscopy (EDS) detector and by inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The resulting materials perform superbly as heterogeneous catalysts for promoting the reaction between aromatic aldehydes and alcohols in the synthesis of aromatic acetals, which play a fundamental role as intermediates in organic synthesis. Optimized conditions allow one to obtain conversions higher than 90% and almost complete selectivity toward acetal products, minimizing, and in some cases eliminating, the formation of carboxylic acid by-products. ICP-OES analysis of the reaction medium allows one to exclude any possible metal-ion release, confirming that catalysis undergoes under heterogeneous conditions. The new metal-loaded CNS can be re-used and recycled five times without losing their catalytic activity.
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