Abstract:

Sustainable development is facing two major challenges: environmental pollution and energy crisis. Solar energy is a sustainable, clean and inexpensive green energy source. Therefore, the efficient use and conversion of solar energy have attracted widespread attention. Metal-organic frameworks (MOF) have gained extensive explorations as a highly versatile platform for functional applications in many research fields. Moreover, Heterostructured MOF-on-MOF composites are recently becoming a research hotspot, which are assembled by two or more different MOF with various structures and morphologies. Compared with single MOF, MOF-on-MOF composites display unprecedented tunability, richer active sites and synergistic effects, which exhibit great application potential in photocatalysis. Therefore, the article mainly reviewed the research progress on the preparation and photocatalytic performance of MOF-on-MOF composites from three aspects: photocatalytic CO₂ reduction, photocatalytic water splitting, photocatalytic degradation of organic pollutants and photocatalytic organic transformation. The synthesis strategies of MOF-on-MOF composites were summarized, including epitaxial growth, surfactant assistant growth, ligand/metal ion exchange and nucleation kinetic guided growth. The characteristics of various strategies were discussed. The advantages of MOF-on-MOF composites were analyzed in photocatalysis. It was pointed out that it was necessary to further improve the precise control and manipulation of MOF-on-MOF with high complexity, explore the clear photocatalytic reaction path and mechanism of MOF-on-MOF, expand the photocatalytic application field of MOF-on-MOF and lay a foundation for the industrial application of MOF-on-MOF.

Key words: metal?organic frameworks, structure-activity relationship, composites, heterostructures, photocatalysis

摘要：

人类的可持续发展正面临着环境污染和能源危机两大挑战，因此，高效利用和转化绿色能源（太阳能）引起了广泛关注。金属-有机框架（MOF）材料凭借其高比表面积、可调孔径和丰富活性位点等特点而逐渐成为光催化领域中一种热门材料。近年来，MOF-on-MOF复合材料成为纳米材料领域的研究热点，其重点是由两种或多种不同结构和形态的同质或异质MOF组装。与单一MOF相比，MOF-on-MOF复合材料表现出更加良好的可调性、更加丰富的活性位点和协同作用，在光催化领域中展现出了巨大的应用潜力。因此，本文主要从光催化CO₂还原、光催化水分解、光催化降解污染物和光催化有机转化这四个方面简述了MOF-on-MOF复合材料光催化性能的研究进展，介绍了MOF-on-MOF复合材料的合成策略，包括外延生长、表面活性剂辅助生长、配体/金属离子交换和成核动力学引导生长等，回顾了各种策略展现出的特点；分析了MOF-on-MOF复合材料在光催化方面的优势，阐述了影响其光催化性能的关键因素。指出需进一步提升高复杂性MOF-on-MOF的精确控制和操纵，探究了明确的MOF-on-MOF光催化反应途径和机理，拓展了MOF-on-MOF光催化应用领域，为MOF-on-MOF的工业应用奠定基础。

关键词: 金属-有机框架, 构效关系, 复合材料, 异质结, 光催化