First of all, when we are dealing with grace it does not matter how smart we are. We can be sure that many people thought that they were smarter than St. Jean Vianney, but he was the instrument of countless conversions. We could say the same for other so called non-academics like St. Joseph Cupertino or St. Catherine of Sienna yet their impact was of historic proportions. Also consider the conversion of St. Augustine, St. Monica and St. Ambrose were the vessels of the grace delivered to Augustine who was perhaps one of the greatest minds the world has ever seen. Therefore it will be your witness of an authentic relationship with Jesus Christ and the Hope and Joy that exists in your life because of that relationship.
However, to satisfy the intellectual side of your friend there are some suggestions. (1) Be honest. There is nothing wrong with saying, 'That is a good question, I'm not quite sure, I will find the answer for you.' If you do say that then you must be sure to follow up. Find the answer and get back to them, otherwise you have jeopardized your own integrity.
(2) Keep studying. Questions that you don't have the answers to are great opportunities for you to deepen your own understanding of the Faith. So keep reading your Bible and Catechism as well as some other trusted authors. Perhaps God has placed this person into your life for your own intellectual development.
(3) In Her 2,000 year history the Church has been able to put together a nice collection of brilliant minds. The chances that your friend is going to ask questions that have not already been answered are probably pretty slim. Of course, there are the bid dogs of the intellectual sphere like St. Albert the Great, St. Augustine, St. Bonaventure, St. Edith Stein, Pope John Paul II, St. Robert Bellarmine, and lets not forget, St. Thomas Aquinas. Unfortunately, many times intellectuals today will discount anyone who came before the Enlightenment (but that would not discount the to Poles, St. Edith Stein and John Paul). There are however many within the Church that have answered the bell of modern man's intellect. This list should get you started: C.S. Lewis, G.K. Chesterton, F.J. Sheed, Fulton Sheen, Peter Kreeft, Alice Von Hilderbrand, and lets not forget a man from Germany named Joseph Ratzinger.
(4) Find a priest that would be willing to spend time with your friend. Most priests would not define themselves as intellectuals, however, to go through the rigourous academia of seminary is not for the faint of mind. Priests usually have a degree in philosophy and at least a masters in theology therefore they have the creditials.