Can I put some references in the research article conclusion to clarify my future work?
The two main functions of a reference are:
- Make sure that you don't take credit for someone else's work.
- As an "external appendix", e.g. "you can read more about this in ..."
If your conclusion contains parts where function 1 applies you have to include the appropriate citations. If your conclusion contains a part where function 2 applies you can do so, but as a matter of style I would be reluctant to do so. A conclusion is there to emphasize the main points of your article. Adding a link to an "external appendix" is not helping.
If the others' work is not relevant enough to be part of the big picture of the problem you lay out at the beginning of the article, then it may not be worthwhile to include it at the end. You can probably write the ending in a way that makes clear that you know people have already done work on it:
These results might prompt us to revisit/further consider a broader/related question: [question]. [While X and Y have notably approached this question, a focus on [some aspect related to paper at hand] may shed new light on the subject.]
If your only reference to the other paper(s) is in the conclusion, do not criticize them. It's not the place for a nuanced critique that is needed in such a situation, plus you don't want to needlessly antagonize those authors and their colleagues, who may be among your reviewers. If a key part of your current research article is the critique of the other research, then it may be appropriate to bring it up again, but try to take the tone in the conclusion of "building on" others' research rather than "correcting their hideous mistake." ;)