During his doctoral studies, Felix participated in different international projects on human rights and related issues. He was a research assistant for the Advancing Child Rights Strategic Litigation project, which aims to promote synergies between research and practice in the area of child rights strategic litigation. Felix also did pro bono work for the International Federation of Red Cross and Red Crescent Societies, contributing to the development of the Global Disaster Risk Management Law Index. As a research associate of the University of Nottingham's Rights Lab, he worked on the 2019 'Measurement, Action, Freedom' Report on the UN Sustainable Development Goal 8.7., by the Minderoo Foundation's Walk Free initiative.

Before joining the University of Nottingham, Félix worked for six years as a qualified lawyer at the Constitutional Court of Colombia. He was responsible for monitoring the following topics related to the protection of the rights of internally displaced persons by violence: humanitarian aid, housing, security measures, protection and restitution of land, and income generation programs. He coordinated and drafted key judgments on these subjects.

Prior to serving at the Court, he worked in the capacity of consultant for the United Nations High Commissioner for Refugees (UNHCR) - Opción Legal in Bogotá, carrying out research on constitutional jurisprudence and international protection standards regarding internally displaced persons.

Felix's current research focuses on the establishment of priorities regarding the guarantee of economic and social rights in post-conflict situations, including the question of the role that reparations should play in these settings. His research addresses the jurisprudence of European, Inter-American and African human rights bodies, as well as the work of the Committee on Economic, Social and Cultural Rights. Felix complements his legal research with moral thinking and contemporary theories of distributive justice, which allowed him to develop a priority setting framework for these contexts.