Metal-organic framework nanosheets (MONs) as the emerging materials have been attracting great interest because the nanosheets possess a range of fascinating attributes including high surface areas and sufficient accessible active sites, and their nanoscale thicknesses are favorable for mass diffusion and transfer of substrates and products with respect to bulk metal-organic frameworks (MOFs). This review first summarizes the synthetic methods of various MONs from top-down and bottom-up methods as well as their diverse composites with different components. Then, the catalytic applications of MON based nanocatalysts are discussed and the relationships among the composition, structure and catalytic performances are revealed. Finally, the challenges and future outlook about the synthesis of diverse MONs and their composites for heterogeneous catalysis are prospected.